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Muetta PLPS 2005 Manual

1. RU WEE Nep ES 42 8 7 dL dI measurement Eta eese eene 42 43 8 9 OSneell D 43 Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com PLPS 2005 user manual 4 1 Introduction The PLPS 2005 Programmable Laser Power Supply is a microprocessor controlled measuring instrument for semiconductor lasers The PLPS is able to drive a laser while the voltage over and the current through the laser are measured Also the reverse clamping voltage of the laserdiode can be measured The monitor diode and or modulator diode can be biased by an adjustable voltage and the diode current is measured A sensitive current measurement range is added to measure the dark current of the monitor diode An external photocell can be biased by an adjustable voltage and the current through it is measured The current through the laser diode can be programmed to the desired value but can also be controlled by the light on the monitor diode the modulator diode or the external photocell Beside the normal DC measurements like laser current laser voltage monitor current etcetera the PLPS 2005 can also dynamically measure the light current slope of the laser at a specific current The PLPS 2005 can be controlled manually or remote by the RS232 or GPIB interface This m
2. 32 5 6 7 Read version ID status error registers en 32 5 6 8 Set Ramp mode read Ramp points 33 5 6 9 Set read E 23 DONO Set read wavelength d addis 34 5 6 11 SeUread photocell sensitivity table eet etre ttai 34 5 6 12 Set read averaging TOO uentos spat pop FR RD PPAR 35 5 6 13 Set read service request 35 y Errors and 36 0D ecc 36 G2 Fatal BEFOL Messages i eod pen Sr CHI Ii cubi edm iaa gia eiaa a RUE lcs n pae 36 6 3 Command error Messages 37 Maintenance orne TET E S ated sy mace een eee 38 Tal S IUE Um 38 7 2 Installing new SOM AUS 38 DSC IT ICALL ONIN P 40 8 1 Driven controlled measured and guarded parameters 40 8 2 Laser connection forward measurements 40 8 3 Laser connection reverse measurement 40 84 Photocell Connection iocus patet nep iyesine Y Massa USER 41 5 9 Monitor digde connection eq id 41 Modulator Connection usce e puits vada pee Vue ete el pte
3. Setlight power W Set monitor current A HAX x Set modulator current A LAR c Valid In remote and remote normal mode Example AL 3e 3 This command sets the desired laser current light power monitor current or modulator current and also selects the control parameter If you for example give a AL 3e 3 command the laser current will be adjusted until the light power on the photocell is 3mW The command can be given in remote off mode but only after a remote normal or remote reverse command the laser current will be adjusted to reach the setpoint 5 6 5 Set read bias voltages Command Answer Description BL BM BX BA BL vi Setphotocell bias voltage V BM vn Setmonitor bias voltage V 1BX vx Setmodulator bias voltage V MBA vLvmvx Set photocell monitor and modulator bias voltage Valid Reading always setting in remote off and remote normal mode Example BL BL 10 Set the bias voltages and read back the setpoints The bias voltages are only applied in normal mode the monitor bias voltage also in reverse mode The bias voltage on the photocell and the monitor diode can be between 0 and 10 volt the modulator bias voltage ranges from 5 to 5 volt Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com PLPS 2005 user manual 32
4. Dark current measurement Mdark range resolution accuracy Limit control Mmax setting accuracy control loop settling time Guard Mmax setting accuracy response time 8 6 Modulator connection Bias voltage Xbias range resolution accuracy internal resistance current limit Current measurement X ranges resolution accuracy Limit Control Xmax setting accuracy control loop settling time Guard Xmax setting accuracy response time 8 7 dL dl measurement Eta superposition current to laser measurement AC photocell current resolution accuracy 1 10 uA 20ms gt 10uA 5ms measurement time incl averaging readout 1 uA 15 bits sign gain 10 offset 10 of range 10 1 of range 10 of range max 1 second Mmax 896 of range 2 20 usec 5 V 11 bits sign 2 5 mV steps 5mV 0 01 Ohm remote sensing 110mA 2 20 200 mA 15 bits sign gain 10 offset 107 of range 103 1 of range 10 of range max 1 second 8 of range 2 20 usec sine 5 KHz 0 3 1 3 mApp 1 10 100 1000 15 bits sign gain 107 offset and noise 10 of range gain 10 offset and noise 10 of range 10 20 50 100 ms 100 0 uW A 2 000 W A Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com PLPS 2005 user manual 43 8 8 Interfaces GPIB standard functions speed write Iset read IVLM message format Serial standard
5. 5 6 6 Set read polarities Command Answer Description Read polarities 1 laser polarity m monitor polarity and x modulator polarity Polarity can be or Set polarities 1 laser polarity m monitor polarity and x modulator polarity Polarity can be or Valid Reading always setting in remote off mode Example P Set the polarities of the laser monitor and modulator diode The laser polarity is the polarity of the current to drive the laser in forward direction If the laser has its cathode connected to COMMON you should select The monitor and modulator polarity is the polarity of the voltage over the diode which is connected in reverse direction If the monitor or modulator has its anode connected to COMMON you should select 5 6 7 Read version ID status error registers Command Answer Description Read version number major minor Read ID string manufacturer type version nr S cpppsmre E nn xxx Get last error Returns an error code followed by a description in plain ASCII or 00 if no errors pending This command clears the error flag in the status string Valid Always Example 2S 00 error IDN gt Muetta Consult PLPS2005 1 01 The 2 query returns PLPS software version number IDN also returns the manufacturer and the type number The 25 command reads the status register A string containing eight characters is retur
6. rtisan tisan Technology Group is your source for quality new and certified used pre owned equipment FAST SHIPPING AND SERVICE CENTER REPAIRS WE BUY USED EQUIPMENT DELIVERY Experienced engineers and technicians on staff Sell your excess underutilized and idle used equipment TENS OF THOUSANDS OF at our full service in house repair center We also offer credit for buy backs and trade ins IN STOCK ITEMS www artisantg com WeBuyEquipment 7 EQUIPMENT DEMOS HUNDREDS OF Instra REMOTE INSPECTION LOOKING FOR MORE INFORMATION MANUFACTURERS Remotely inspect equipment before purchasing with Visit us on the web at www artisantg com 7 for more our interactive website at www instraview com 7 information on price quotations drivers technical LEASING MONTHLY specifications manuals and documentation RENTALS ITAR CERTIFIED Contact us 888 88 SOURCE sales artisantg com www artisantg com PLPS2005 User Manual Manual control and remote programming Author Werner Damman Date 01 02 27 15 40 Document nr 833 05 01 Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com PLPS 2005 user manual 2 1 3 4 Contents Iirinssisitom 4 MESE RT T 4 Visio P 6 21 Placement and connection cece 6 2 2 Mai
7. Max modul Max Eta length Laser pol Wave larity Monitor polarity Modul lator polarity M lator current X EASUR E SYST EM 190 00 0 200 1200 positive positive positive LSENS MAIN e Wavelength This sets the wavelength of the laser light Using the photocell responsivity table the sensitiveness of the photocell is calculated If a non specified value is given the nearest value in the table is used e Laser polarity Specifies the polarity of the laser current to drive it in forward direction Positive means that the laser diode has its cathode grounded connected to COMMON Monitor polarity Specifies the polarity of the bias voltage to put the monitor diode in reverse direction Positive should be selected if the anode of the monitor is grounded connected to COMMON e Modulator polarity Specifies the polarity of the bias voltage to put the modulator diode in reverse direction Positive should be selected if the anode of the modulator is grounded connected to COMMON The sign of the settings and measured values I V L M X E is such that a higher value stands for more light Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com PLPS 2005 user manual 14 3 4 The MEASURE menu In the MEASURE menu some measurement method adjustments can be made To select the MEASURE menu you should press OFF the
8. format flow control Laser monitor modulator interlock connector interlock input Photocell connector floating connected shield Interlock Trigger in out L V L M X connector trigger input trigger output I V L M X outputs 8 9 General Dimensions Weight Environmental conditions temperature relative humidity Power consumption 488 1 1987 Talker Listener Remote trigger Serial poll 4 50 msec at Iset step 0 1 100 5 20 msec at dL dI measurements ASCII text or IEEE binary floats RS232C DB9 male connector with locking 9600 38400Bd 8 bit data no parity 1 stopbit Hardware RTS CTS DB15 female with locking TTL level internal pullup 20 us filter for switch Must be grounded to enable laser DB9 female with locking DB15 male with locking TTL level internal pullup TTL level 10V fullscale single ended Rload minimal 10kOhm 364 x 120 x 376 mm wx hx d approx 6 kg 15 35 C 20 90 non condensing 230 115V 50 60Hz 100W Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com rtisan tisan Technology Group is your source for quality new and certified used pre owned equipment FAST SHIPPING AND SERVICE CENTER REPAIRS WE BUY USED EQUIPMENT DELIVERY Experienced engineers and technicians on staff Sell your excess underutilized and idle used equipment TENS OF THOUSANDS OF
9. PLPS 2005 user manual 11 3 2 Control basics After power on the PLPS shows the startup screen for a few seconds During power on an automatic self test takes place If problems occur during this test the display will show an error message See also the chapter errors Attention If this is the first time you use the PLPS do not select the NORMAL RAMP or REVERSE mode First check the settings before you turn on the laser After the self test the PLPS will switch to the OFF mode The indicator in the OFF key is lit and the screen looks like below Iset 100 004 This is the default screen At the left the actual measured values are showed I the laser current V the voltage over the laser L the light power M the monitor current X the modulator current E the dL dI value In the OFF mode the laser output is shorted and the current source is disabled so the measured current and voltage are at or near zero The modulator and monitor diodes are disconnected so no current will flow here too The photocell however is connected but not biased and shows the actual light power The right part of the screen shows Iset with a current in mA This setpoint can be altered by rotating the knob The Iset value is the desired laser current If you turn on the laser by pressing the NORMAL button the current source will be set to this value By pressing the keys you can select another control pa
10. 1 Introduction The PLPS can be remote controlled completely After powerup the PLPS 2005 starts in local mode and the front controls are active If control is taken via GPIB or RS232 the PLPS switches to remote mode the front controls are inactive now In remote mode the display and the LED indicators in the keys will reflect the actual state of the PLPS Remote reading of measurements and settings is always allowed even in local mode If the PLPS 2005 is in remote mode you can enter local mode manually by pressing successively the REVERSE RAMP NORMAL and OFF button Before remote control can be used you should select and configure the desired communications channel GPIB or RS232 This is done manually by the front controls in the SYSTEM menu See also the chapter Manual control 5 2 Command structure commands in plain text ASCII At the GPIB interface an EOI command should be sent together with the last character of the command A carriage return and or a linefeed is allowed but not mandatory If you use the RS232 interface a carriage return and or linefeed at the end of the command is mandatory A command starts with a to change a setting or with to request a setting measurement Following that a one or two character command is given followed by and one or more parameters if applicable Parameters are separated by a comma a colon a semicolon or a slash parameters are given an
11. ROM are damaged Press function key 3 during power on to invoke the serial downloader You should start the programming procedure again To check the current firmware version you can press the left function key during power up The top row of the display will show the software version number and release date Press another key to continue Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com PLPS 2005 user manual 40 8 Specifications 8 1 Driven controlled measured and guarded parameters Item Drive Measure Guard Laser I LV E Imax Vmax Photocell Lbias L Lmax Monitor Mbias M Mmax Modulator Xbias X Xmax 8 2 Laser connection forward measurements Current drive Iset ranges 0 2A en resolution 15 bits sign accuracy gain 10 offset 10 of range output voltage superposition current for dL dI measurement range waveform Current measurement I ranges resolution accuracy Voltage measurement V range resolution accuracy measurement method 8 3 Laser connection reverse measurement Current drive Iset range resolution accuracy output voltage Voltage measurement V range resolution accuracy max 8V 0 3 1 3 mA pkpk sine 5 kHz 0 2 en 15 bits sign gain 10 offset 107 of range 10V 15 bits sign gain 10 offset 107 of range remote sensing 1 200 uA uA 1 max 30V t30V 15 bits sign 30 mV Artisan Tec
12. SYSTEM THe screen should look like below Remote via GPIB address 5 GPIB msg terminator EOI RS232 baudrate 19200 RS232 flow control RTS CTS String termination CR LF 2 DEVICE MEASURE LSENS MAIN The 4 symbol at the bottom indicates that more rows are available by pressing the J key The settings can be altered by selecting the desired parameter using the 7 keys and then rotating the knob To leave the menu you can press the OFF or MAIN key Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com PLPS 2005 user manual 15 RS232 baudrate RS232 flow control String termination LCD contrast LCD brightness Bar graphs MAIN The following settings can be made Remote via PLPS be remote controlled using RS232 or GPIB Here you select the desired interface GPIB address The GPIB interface answers on a primary address from 0 to 30 GPIB msg terminator Determines how to delimit the outgoing GPIB messages The most usual setting is EOI The PLPS always responds on the incoming EOI e RS232 baudrate The desired RS232 baudrate You can select 2400 to 38400 baud RS222 flow control You can select NONE no handshaking or RTS CTS In that case the RTS output will become inactive if the incoming data buffer almost overflows If the CTS input is inactive the PLPS will stop transmi
13. also during a Ramp In OFF mode the PLPS is in the following state e laser driver is turned off and the laser input is shorted to COMMON The shorted laser output protects the laser against static charge build up The photocell is still connected to the photocell amplifier so the light measurements are still active The photocell bias voltage however is 0 volt e The monitor and modulator diode connectors are in high impedance state 10 and the bias voltages are off The display shows the actual measurements of which only the light measurement has any relevance and the I V M or X setpoint or the bias voltage setpoints Only in OFF mode it is possible to alter the laser settings maximum values polarities etcetera In OFF mode it is safe to remove or connect the laser The interlock input may now be opened without causing an error message Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com PLPS 2005 user manual 22 4 5 NORMAL mode If the NORMAL key is pressed or a remote NORMAL command is given the PLPS enters the following state The bias voltages are applied to the photocell the monitor diode and the modulator diode The laser is no longer shorted The laser driver is enabled The laser current is adjusted until the setpoint is reached The display shows the actual measured values and the setpoint In NORMAL mode the screen l
14. at our full service in house repair center We also offer credit for buy backs and trade ins IN STOCK ITEMS www artisantg com WeBuyEquipment 7 EQUIPMENT DEMOS HUNDREDS OF Instra REMOTE INSPECTION LOOKING FOR MORE INFORMATION MANUFACTURERS Remotely inspect equipment before purchasing with Visit us on the web at www artisantg com 7 for more our interactive website at www instraview com 7 information on price quotations drivers technical LEASING MONTHLY specifications manuals and documentation RENTALS ITAR CERTIFIED Contact us 888 88 SOURCE sales artisantg com www artisantg com
15. is fairly linear Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com PLPS 2005 user manual 18 To lower the photocell capacitance and to avoid the effects of the internal resistance you can apply a reverse bias voltage over the photocell The voltage is adjustable and is indicated as Lbias on the PLPS 4 1 3 Eta The PLPS is able to measure the slope of the characteristic on a specific point This is the change of light as a function of a small change of the current This the dL dI or Eta value in Watt per Amp re W A If you draw a graph showing the laser current on the horizontal axis and the Eta on the vertical axis the following picture appears Eta Current With semiconductor laser the Eta is small when the laser current is below the threshold current If the threshold current is exceeded the Eta grows very fast and then remains almost stable until the maximum allowed current Current Eta values are 0 1 0 5 Watt per Amp re The Eta graphs shows the laser linearity You can also trace small irregularities in the L I characteristic the so called kinks The Eta measurement function of the PLPS is less suitable to determine the overall Eta of the laser If you want this you can do a statistic calculation over the L I characteristic this will be more accurate 4 1 4 Monitor measurements If the laser has a built in monitor diode you can me
16. monitor modulator current is reached The IVLMXE measurements are stored per point e After a maximum has been reached the current remains at its present value During the ramp the screen looks like this Ramping 845 At the left the actual measured values are shown at the right the RAMP progress is displayed If the Eta function is activated during the ramp the ETA indicator is active The maximum number of points measured during the ramp can be set just as the measure time per point With longer measurement times per point more measurements per point are averaged resulting in less noise and more accuracy If the Eta function is enabled the measure time per point can never be below the Eta measurement time setting Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com PLPS 2005 user manual 25 During the ramp current is incremented with fixed steps The step size is determined as following maximum current start current number of points This means that if the maximum light is reached before the maximum current the measured number of points is less than the number of points in the setup Therefore you should always read the number of points before processing the ramp data 4 7 REVERSE Mdark mode If you select REVERSE mode this is only allowed from OFF mode or you give a remote REVERSE command the following happens The monitor bias voltage is appl
17. potential at or near The photocell input is primairily intended to connect a photocell It has however limited capabilities for connections to other equipment like an external photocell amplifier with a voltage output In that case you should care that the voltage output swing of the external equipment is as large as possible for example 0 to 10 volt Connect the output using a series resistor to the terminal the virtual ground input Calculate the series resistor for a maximum current of mA 10k for 10V The common terminal of the external amplifier can be connected to the shield terminal of the photocell connector on the PLPS or better with the analog ground terminal of the AUX connector 2 7 Aux connector On this connector a couple of additional signals are available You can connect an external oscilloscope to examine the amplified and scaled IVLMX signals Also available is an Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com PLPS 2005 user manual 8 external trigger in and output to synchronize the measurements In the current embedded software version 1 10 the trigger in and output have no use Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com 9 PLPS 2005 user manual OL Q3 0NnO35 iN3W4dInO3 118 18 43559 43597 DNILIUO014 HLIM SI NO
18. the modulator diode use a common return the monitor diode has its own return All laser terminals are connected using a drive and a measure wire This is done to compensate the voltage drop over the cable See the wiring diagram at the end of this chapter for a wiring example The cable to the laser should be shielded to introduce as little interference as possible Warning The shield is internally in the PLPS connected to the COMMON socket at the rear panel and with the return drive wires of the laser modulator and the monitor The LASER connector also contains the safety switch input The PLPS cannot drive the laser if this contact is not shorted to COMMON This can be done using a door contact which shorts when the door is closed to prevent a user from looking in the laser while it is active The safety input is internally tied to 5V using a pull up resistor The PLPS switches OFF if the safety input is interrupted for more than 10 microseconds 2 6 Photocell connection On the PHOTO connection you can connect a photocell The two terminals of the photocell are both connected using a drive and a measure wire like the laser connections The photocell cable should be shielded IMPORTANT Both photocell terminals must be floating and may not be connected to earth One terminal the cathode is connected to the bias voltage source 0 to 10 volts the other the anode is connected to a current input This is a virtual ground input and has a
19. you enable the service request for that flag After powerup all bits are cleared no service requests See for more information the paragraphs serial poll byte and service requests Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com PLPS 2005 user manual 36 6 Errors and troubleshooting 6 1 Self test The PLPS will perform a self test during power up The integrity of the Flash memory and the stored settings is checked and a thorough hardware test is performed If errors are found during the self test the display shows a message and would look like this Version 1 00 Jan 01 2000 Cal Jan 01 2000 Reading config Reading calib Reading responsivity Reading meas setup Serial Gpib port init Analog board init Selftest The top row shows the firmware version number and release date followed by the latest calibration date In the following rows the self test steps and their results are showed If the program code itself is damaged another screen appears This can be caused by a failed attempt to update the software See for more information the chapter Maintenance installing new software If Reading config Reading responsivity or Reading meas setup fails you should check all settings Possibly something went wrong at the moment the settings were stored If the error occurs frequently you should contact your supplier An er
20. FEM Ligula 20 4 24 eric tee ee 20 AUB E i E i aa KAS cecteeees ee ecc tute eeu pee eee d etes 21 21 4 3 NORMAL 000 6 cere e tbt cete tt temi cu ee i E care 22 A51 Changing PI NNUS Ea ee 22 45 2 HOLD PONG OMe icto eet eee reete dte eta eet 22 4 5 3 JETDAUUnDC ODC es reete tereti ete treten ente erede 23 CI DATO 23 4 6 eee c EG ee Ee PE edet 24 47 REVWERSE Mdark mode cette tte tentent 25 Remote CONTO cs c teret OH rH 26 5 1 Introduction Eee cete baee tete 26 5 2 Command 26 53 Sc DIU A 27 ST GPIB seral poll SAET ENST RER 27 523 GPIB 5 se aneii s Ea EERE aaia E e iia ES aE 28 5 6 Command overview 29 Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com PLPS 2005 user manual 3 5 6 1 Setoperating 29 2252 Read actals ion I TEM 29 SUE ME CU nn 30 JOGA BCU Se IN ean sneer eee 31 5 5 3 Setread Dias vOllaBes Vr te aM LUE 31 2 000 Set read
21. IIUDLlIS 1538 JHL 835012 38 LSAW SX 01 ANIT AHL AO 13395 01 Q3123NNOO 150 55 43587 3 B3Hl1I3 ALON gt a01 INOW ONNOAD A134US 3LON gt a01g1n00A4 43597 1 310N 11010 y 1132010 S00cSd ld 3194340 01 035012 38 5 HILINS 5207831NI A01 INON QNnOaND A134US ALON 40181n00A4 43597 1 43581 01 Q3123NNO2 3OL1INOU AOLINOW 3183Bd3S 6x SNIUH Q13IHS DU 5120 1431NI 8131 5 32404731 35435 7 33803 01 35435 97 07131 5130 12431NI 3SN3S OND ISNS NOH NOH 3SN3S QND 807 3SN3S Q0H 3535 5071 587 3592 ONY QNNOaD 134385 QNhO3D S231NO2312313 103 2010 Ia 512 sla asa 10 Ia 12 514 asa ala 31892 17NN 1803 402 26254 Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com PLPS 2005 user manual 10 3 Manual control 3 1 Front panel PROGRAMMABLE LASER POWER SUPPLY P U d un The front panel contains three groups of controls With the four keys on the left the measurement function of the PLPS is chosen The keys hav
22. RE with settings related to the measurement method SYSTEM where you can change system specific settings like display contrast or RS232 speed LSENS where you can edit the photocell responsivity table The settings in these menu s will be described in detail in the following paragraphs 3 3 The DEVICE menu The DEVICE menu screen shows all settings which are laser dependent here you can enter the datasheet of the laser To enter the DEVICE menu you should select mode OFF then press MENU The screen will look like below laser current I 100 00 mA laser voltage V 8 000 V light power L 1 000 mW monitor current M 10 000 mA modulator current X 190 00 uA Eta 0 200 W A 4 ENS If another menu is selected you should press DEVICE to show the DEVICE menu The J symbol at the bottom indicates that more rows are available by pressing the J key The settings can be altered by selecting the desired parameter using the Tl keys and then rotating the knob To adjust the decimal point press the lt gt keys The menu is left by pressing the OFF or MAIN key The following settings are available Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com PLPS 2005 user manual 13 Max laser current This sets the maximum allowed laser current before it will be damaged The actual current will be limited to this current If you for
23. anual describes the use of the PLPS 2005 with firmware version 1 10 or higher 1 1 Used terms In this paragraph some terms are explained which are used further in this manual The laser diode is a semiconductor diode with two terminals which when driven with a forward current above a specific threshold will emit coherent laser light Because only in a part of the total current range laser light will be emitted the dL dI light change for a specific current change can be high Because the laser diode behaves like a normal diode the voltage over the diode as a function of the current is logarithmic If the laser conducts small voltage changes will result in large current changes Therefore it is not practical to drive the diode with a voltage Source so a current source is used in the PLPS2005 The laser package often contains a monitor diode This is generally a PIN diode which if shorted or biased in reverse direction supplies a current which is proportional with the laser light on the monitor diode This current can be used to stabilize the optical output of the laser The package can also contain a modulator diode This diode is placed so that the laser light output flows through it By varying the voltage over the modulator diode the light output is controlled Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com PLPS 2005 user manual 5 To measure the emitted
24. asure the monitor diode current as a function of the laser diode current The current through the monitor diode is almost proportional to the laser current as with the photocell The characteristic of the monitor current M as a function of the laser current the M I characteristic looks exactly like the L I characteristic From this characteristic and the L I characteristic you can calculate the monitor diode responsivity in A W To lower the monitor diode capacitance and to avoid the effects of the internal resistance you can apply a reverse bias voltage over the monitor diode The voltage is adjustable and is referenced to as Mbias on the PLPS Another monitor diode parameter you can measure with the PLPS is the so called dark current or Mdark If no light falls on the monitor diode a small leakage current will flow To measure this current a separate sensitive current measurement range is available Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com PLPS 2005 user manual 19 4 1 5 Modulator measurement Some lasers have a modulator diode to control the light emission of the laser diode The current through the modulator diode behaves like monitor current and is almost proportional to the laser light output Besides that the modulator acts like an optical regulator the amount of light which comes through it depends on the voltage over the modulator diode This v
25. aution The instrument is default shipped for 230V mains If your mains voltage is 115V you should also change the fuses See the table at the rear panel for the correct value The mains inlet also contains the power switch 2 3 GPIB RS232 The GPIB cable is connected to the centronics style GPIB connector The GPIB address can be set using the front panel The RS232 connector is a 9 pole male D type and is wired like a DTE as a PC com port To connect the PLPS with a PC using RS232 a null modem cable should be used The baud rate and handshake mode can be set using the front panel 2 4 Earth terminals At the rear panel two 4mm sockets are available for external earth connections You can ground your measurement setup using the COMMON socket The COMMON socket is internally tied to the common electronics ground The PE socket can be used to make an Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com PLPS 2005 user manual 7 extra protective earth connection this socket is internally tied to the case and the mains earth If the laser photocell setup is electrically floating you can short the PE and COMMON terminals If the measurement setup is grounded somewhere e g via another test instrument you should leave the COMMON and PE terminals floating 2 5 Laser connection Using this connector the laser including the modulator and monitor diode is connected The laser diode and
26. complete set of data measured at the same time you should use the AA or AB command This guarantees that all measurements are done with the same laser current The AB command returns the data in binary format 4x6 24 bytes After sending a new setpoint or changing the measurement mode you can check the DAV bit in the serial poll register to determine if valid new data is available Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com PLPS 2005 user manual 30 In reverse mode you can read the V and M actuals The reverse voltage is clamped to 30V a returned voltage above 30V indicates that no valid measurement could be done In reverse mode the actual current is NOT measured the AI command returns the setpoint instead 5 6 3 Set read limits Command Answer Description 57 O Set maximum laser current A Set maximum laser voltage V Setmaximum light power W MM m maximum monitor current A NENNEN La Set maximum modulator current A Set maximum ETA W A Set maximum I V L M X E Valid Reading always set only in remote off mode Example IMA 4e 2 3 10e 3 2e 3 1 This command sets the maximum laser current laser voltage light power monitor current modulator current and Eta The maximum values can only be set if the PLPS is in remote off mode The maximum laser current is the maximum
27. current which causes no damage to the laser The laser current will never exceed this current When controlling the light output the current is also clamped to this value The set range is 100uA to 1A The maximum laser voltage is the maximum allowed voltage over the laser If this voltage is exceeded the guard circuit will directly turn off the laser The set range is from 0 to 8 Volt The maximum light power is the maximum amount of light the laser may emit Together with the values in the photocell responsivity table this determines the maximum allowed photocell current The photocell current is limited to 100 The maximum light power you can set depends on the photocell responsivity If the maximum light power is exceeded the laser current will be decreased The maximum monitor current is the largest current allowed for the monitor diode If this current is exceeded the laser current will be decreased The set range is 0 to 100 mA Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com PLPS 2005 user manual 31 The maximum modulator current is the largest current allowed for the modulator diode If this current is exceeded the laser current will be decreased The set range is 0 to 200 mA The maximum is the largest which can reliably be measured The set range is from 0 1 to 5 W A 5 6 4 Set setpoint Command Answer Description Set laser current A
28. d no parity 8 databits 1 stopbit no handshaking Then power up the PLPS while pressing the third function key under the display The PLPS display will now show PLPS 2005 Bootloader V1 2 Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com PLPS 2005 user manual 39 And the terminal screen shows PLPS2005 bootloader version 1 2 Enter E1234 to erase flash and upload Intel HEX or press space to continue the normal startup procedure At this moment you can cancel the procedure by pressing the spacebar of turning off the PLPS If you want to continue you should enter E1234 note the capital E The terminal shows 12345 Erasing flash Start Intel hex upload now The old firmware is now erased Select ASCII upload on your terminal program and select the file containing the new firmware The PLPS firmware is supplied to you as an Intel HEX file with file extension for example plps2005 hex Start the upload The PLPS is programmed during upload The terminal screen shows dots or p s for each row in the Intel hex file If programming has ended and was successful the PLPS will start with its normal opening screen If programming failed or if the contents of the Flash ROM are damaged the following message appears on the display after power up PLPS 2005 Bootloader V1 2 Checksum error in program memory The contents of the flash
29. d read back as floating point numbers and in SI units Volt Amperes Watts meters etcetera Numbers may have leading zeroes If you send a setpoint that is out of range or omit a setpoint the setting is not altered If you give a command starting with a the PLPS will return a string containing the command without followed by the requested data and terminated according to the setup in the SYSTEM menu If more than one parameter is returned the parameters are separated by commas Exceptions are the IDN command and the read binary commands AB and QB The last will return the data in binary format as 4 byte floats without CR and or LF This format has the advantage of higher transmission speed less data to transmit and no conversion to from ASCII necessary The format is IEEE standard float MSB first Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com PLPS 2005 user manual 27 Some command examples 010 34e 3 I set to 10 34 mA ML Request maximum light power answer ML 4 5497e 4 Maximum light power is 0 45497 mW IMM 0 045488 Set maximum monitor current to 45 488 mA 5 3 Error handling If an invalid command is received the error flag in the statusregister will be set and the command will be ignored from that point If an internal error occurs e g the laser voltage reaches its limit the error flag is set too The application should regula
30. e built in LEDs indicating the current state of the PLPS OFF In the OFF mode the laser output is shorted and the bias voltages are zero volt NORMAL Current flows through the laser and the bias voltages are present RAMP The laser current will increase until the maximum current or light output is reached REVERSE A small reverse current flows through the laser diode and the laser voltage is measured Also the monitor bias voltage is applied and the monitor dark current is measured With the knob on the front panel the PLPS settings can be adjusted The buttons placed under and besides this knob have the following functions FAST If this function is active the setting will change ten times faster if you rotate the knob e LOCK If this function is active rotating the knob has no effect This prevents the user from accidentally changing a setting lt gt With this keys you can adjust the position of the decimal point if applicable The display shows the menu s the current voltage setpoints and the measured values The display is lit but the backlight can be disabled You can also optimize the display contrast The function of the five keys beneath the display window is showed on the display The keys with the Tl symbols be used to select another control parameter or scroll through the menu s Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com
31. er Description Read wavelength m Set wavelength m Valid Reading always set only in remote off mode Example W 1350e 9 This command sets the light wavelength Using the photocell sensitivity table the sensitivity for this wavelength is determined If the exact wavelength is not found in the table the nearest value is used 5 6 11 Set read photocell sensitivity table Command Answer Description HIN DNennps Read nr of entries in photocell responsivity table LP w r r Read next wavelength responsivity entry in m A W LR IRs Read currently used responsivity in A W m Delete all entries new entry in m Valid Reading always setting in remote off mode Example LN 5 LN 7 ILI 950 9 0 35 The PLPS returns the light power measured with the external photocell in Watts To do this the photocell responsivity in per Watt must be known The PLPS has memory to store up to 40 different wavelength sensitivity pairs The number of sensitivity points can be requested by the 7LN command This command sets the read pointer to the first point of the table If points are available you can read them one by one using the LP command The table can be cleared with the LD command With LI you can insert new points to the table The sensitivity used depends on the wavelength If a wavelength is set which not appears in the table the nearest value will be selected I
32. example control the laser by the light power the current will be clamped to this maximum even if the desired light power is not reached The setting ranges from 100uA to 1A Max laser voltage This is the maximum allowed laser voltage If this voltage is exceeded the PLPS will turn off the laser and generate an error message Max light power Sets the maximum light output allowed for the laser The setting is in Watts the actual maximum photocell current is calculated using the sensitivity table see below The photocell current is limited to 100mA the maximum light power depends on the sensitivity of the photocell If the light output exceeds the maximum value the laser current will be decreased If this fails the PLPS will turn off the laser and generate an alarm Max monitor current The maximum allowed monitor current If this value is exceeded the laser current will be decreased If this fails the PLPS will turn off the laser and generate an alarm Max modulator current The maximum allowed modulator current If this value is exceeded the laser current will be decreased If this fails the PLPS will turn off the laser and generate an alarm Max ETA Here you specify the largest expected ETA This setting is used to select the correct range and will not generate errors if exceeded Note The measurement ranges are determined using the Max values If you select a far too high maximum the measurement accuracy will decrease substantially
33. f no entries are made a sensitivity of 1A W is used After the wavelength is set you can query the calculated sensitivity Using this sensitivity you can calculate the actual photocell current Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com PLPS 2005 user manual 35 5 6 12 Set read averaging mode Command Answer Description ______ Read averaging mode 0 off 1 Gom Setaveraging mode 0 off 1 on Valid Reading always set in remote off mode Example gt If the averaging mode is enabled the PLPS will after the setpoint is reached average the measurements This strongly reduces noise on the measurements To see if averaged data is available you should wait until the averaged data available flag in the serial poll byte is active 5 6 13 Set read service request mask Command Answer Description H f Read service request mask register H f Write service request mask register f is a byte value containg any combination of the following bit flags RAMPDAV bit2 4 DAV bit3 8 AVGDAV bit4 16 ERR bit 5 32 Valid Reading always set in remote mode only Example 48 SRQ if ERR or AVGDAV are set The PLPS can generate a GPIB service request if one or more of the flags stated above are set Which flags will generate a service request is defined by the bits in the service mask register By setting bits
34. hnology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com PLPS 2005 user manual 41 8 4 Photocell connection Bias voltage Lbias range resolution accuracy internal resistance current limit Alternative Lbias negative Rin current limit Light measuring L current ranges resolution accuracy 0 1 100mA 0 01 mA settling time 10046 step to 0 196 0 01mA 0 1 100mA wavelength correction table wavelength setpoint conversion factor maximum allowed photocell capacitance Limit control Lmax setting accuracy control loop settling time Guard Lmax setting accuracy response time 8 5 Monitor diode connection Bias voltage Mbias range resolution accuracy internal resistance current limit Current measurement M ranges resolution accuracy 10 V 11 bits sign 1 10 mV max 0 1 Ohm 150 mA 20 Ohm 5 150 mA 0 01 0 1 1 10 100 mA 15 bits sign gain 10 offset 107 of range gain 10 of range offset noise 5nA lt 30ms lt 3ms up to 40 pairs using the closest match 100 9999 nm 10 10 A W 10 nF 103 1 of range 10 of range above 0 1mA range max 1 second Lmax 896 of range 2 20 usec 11 bits sign 10mV max 0 1 Ohm 150mA 1 10 100 mA 15 bits sign gain 10 offset 107 of range Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com PLPS 2005 user manual 42
35. ied The laser short is removed The laser driver is enabled and set to the reverse current setpoint The screen shows the actual measured voltage and the reverse current setpoint screen should look like below I 10 0 uA Ireverse 10 Oua V 18 451 V M 0 000 uA At the right of the screen the reverse current setpoint is shown To the left you see the actual laser voltage the actual monitor current and a copy of the Ireverse setpoint The shown I value is NOT the measured value If you read the actual current via the remote interface you will also get the setpoint not the actual measured value Because the laser will not light during reverse measurements we can also measure the monitor leakage current the dark current The measure range is 1 uA full scale independent of the maximum monitor current setpoint The laser voltage is clamped to 35 volt max If the voltage over the laser exceeds 30 volt the screen will show open Keep in mind that the measure time with small reverse currents and long cables can be longer due to cable capacitance The cable capacitance must be charged first If you control the PLPS manually you can see when the measured voltage is stable using remote control you have to insert a delay before reading the reverse current Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com PLPS 2005 user manual 26 5 Remote control 5
36. ing an optical attenuator this means that not all the laser light arrives at the photocell surface you have to recalculate the photocell responsivity using the attenuation An example imagine a setup using an optical sphere The sphere has two openings one at the bottom in which the light to measure enters and one at the side where the photocell is mounted The sphere has an optical attenuation of 100 times The photocell responsivity is 0 3 A W The responsivity in the responsivity table should be set to 0 3 100 0 003 A W 3mA W NB If the photocell responsivity is incorrect this will not only affect the light measurements but also the Eta readings Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com PLPS 2005 user manual 20 4 2 2 IVLMXE maxima There are several reasons to enter the correct values for the maximum values to protect the laser but also because the PLPS determines its measurement ranges using the max values If an I L M or X maximum is exceeded the PLPS will decrease the laser current until the parameter is below the limit If current decrease has no effect and the maximum is exceeded by more than 5 the built in hardware guard circuit will turn off the laser completely If the V maximum is exceeded the current will not be decreased but the hardware guard will directly turn off the laser More information about the hardware guard can be found below The E
37. iode is in forward direction and not too small the voltage about the laser will be about 1 2 volts If the voltage V as function of the current I is shown in a graph the following picture appears Voltage Current The PLPS has the possibility to drive the laser with a small reverse current in the micro ampere range The cathode of the diode is then positive This is called the reverse mode In reverse mode you can measure the leakage resistance and the reverse voltage over the laser 4 1 2 characteristic The most fundamental measurement is the light output L of the laser as a function of the laser diode current I If the light output is measured using a photocell photo diode connected in reverse then the current through the diode is practically proportional to the light on the photo diode The PLPS measures the photocell current in Amp re and divides it through the light sensitivity of the photocell given in per Watt to get the light power in Watts If the measured values are shown in a graph the so called L I characteristic arises See below Light Current When the current is low the laser diode acts like a LED and emits a small amount of incoherent light If the current exceeds the so called threshold current the laser starts emitting the real laser light and the curve rises steeply With most lasers the light increase as function of the current increase from the threshold point
38. le COMMON you can set the polarity for the diode currents voltages A positive laser polarity is selected when the laser has its cathode connected to the common terminal This will cause a positive current to drive the laser diode in forward direction At the monitor and modulator diode a positive polarity means that the anode is connected to the common terminal A positive voltage is then applied to the diode The diode will not conduct then this is the normal use The sign of the settings and actual readings L M X E is always so that a higher value means more light Maximum values the setpoint and bias voltages are generally positive An exception is made for the modulator bias voltage Xbias this voltage can be slightly negative so that the diode almost conducts Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com PLPS 2005 user manual 21 4 3 Guards When setting up the PLPS you have entered maximum values for L M and X These values are guarded by software Each time a new laser current is set a check on the maximum values is done The laser current can never change more than 1 of the maximum laser current If the maximum laser current is set correctly a 1 current change will never change the light output and thus the monitor modulator current by more than a few percents so worst case the light output will exceed the specified maximum by a few percent
39. light power an external photocell can be connected The electrical and optical parameters of the laser the monitor the modulator and the photocell will be represented in this document by the following abbreviations Parameter Units Laser diode current Laser diode voltage Mentor diode curent __ M Modulator diode current X dLdlor ITTA EB Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com PLPS 2005 user manual 6 2 Setup The chapter describes how to connect the PLPS 2005 See also the wiring diagram at the end of this chapter 2 1 Placement and connection The drawing shows the rear panel of the PLPS 2005 It contains the connectors for the laser the photocell external control etcetera When installing and connection the PLPS you should take care to let free the ventilation slots in the bottom and the rear of the case If the PLPS is used as a table top instrument you can fold back the front feets at the bottom of the instrument ype PLPS 2005 T 5 115 250 50 60Hz 2 2 Mains connection Before the PLPS is powered you should check the mains voltage setting You can select both 230V and 115V using the fuseholder Take it out and put it back the other way round to select the other voltage The setting shown in the drawing above is for 230V C
40. n MENU and then MEASURE The screen should look like below Ramp step time Ramp nr of steps Eta measure time Eta current VLMX averaging reverse ICE Using the 7 keys you can select a parameter The selected value can be changed by rotating the knob To leave the menu you can press MAIN or OFF The next settings can be made Ramp step time During an automatic ramp the PLPS will measure each point during this time Note that if you use the ETA function the ramp step time cannot be shorter than the ETA measure time Ramp nr of steps The maximum number of measurement points during a ramp The actual measured number of points can be smaller if the maximum light power on the photocell or monitor diode is reached before the maximum current is reached average time The measurement time per point for the measurement A longer time gives a more accurate ETA measurement current The modulation current used for the measurement in mA peak peak You can select 0 3 1 or 3 mA peak peak VLMX averaging If you select this function the PLPS will as soon as the setpoint is reached average the measurements This decreases the noise on the measured values e reverse The default laser current during the reverse measurement 3 5 The SYSTEM menu The SYSTEM menu shows the system specific settings You select the SYSTEM menu by pressing the OFF key then MENU and then
41. n can be any value between 100 and 2000 this value is rounded off to 100 200 500 1000 or 2000 This number can turn out smaller if the maximum light on the photocell or the monitor modulator diode is reached before the maximum current is reached The ramp is started with the K 4 command If the ramp is finished you can check it with a serial poll you should request the actual number of measured points using the R command This command also resets the point counter to the first point in the array Then you can read the measured point one by one using the 705 command or you can read them all at once using the QB command In the last case a binary block of data sized 24 times the number of points is transmitted 5 6 9 Set read dL dl setting Command Answer Description Read dL dI mode 0 1 A s D onitavg SetdL dl mode On 1 on or 0 off Valid Reading always set in remote off mode only Example D D 1 0 3e 3 20e 3 Set the various Eta measurement parameters i is the modulation current in Amp re peak peak and can be 0 3 1 or 3 mA and must one of these values The tavg is the Eta measure time and can be 5 10 20 50 or 100 milliseconds If you specify another time it will be rounded off to the nearest value Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com PLPS 2005 user manual 34 5 6 10 Set read wavelength Command Answ
42. ned or R L is local control R is remote control ppp Laser monitor and modulator polarity p is of S or Status of the safety switch ok S switch open N S or Mode is off Normal Single ramp or Reverse s T L or X Control loop parameter is out of band of ramp busy or E Error flag status E is error pending ongoy E reads the error register and clears the error flag See also the chapter Error messages Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com PLPS 2005 user manual 33 5 6 8 Set Ramp mode read Ramp points Command Answer Description Read ramp speed in number of points time per point n Is F nmn length and speed n Is Read number of IVLMXE points buffer Q i up eta Read IVLMXE point from the buffer QB bbbbbbbb Read all IVLMXE points from the buffer in binary format Each point is 24 bytes 6 floats of 4 bytes each Valid Reading always setting in remote off mode Example R R 854 205 QS 3 47e 2 2 21 12 24e 3 4 3e 3 5 1 3 0 235 While executing an automatic ramp the PLPS will measure the laser parameters during the time per point Times between 0 and 1 second can be set these are round off to the nearest value in 1 2 5 steps With nnnn you can specify the maximum number of points for the ramp Nnn
43. ns 6 2 3 5232 20 ERE exe vue eeu peek es deve eese voee v uve ees vu THREE UNS 6 24 Earth terminals 5e 6 2 9 aser connectlon eee cea re tete i tete ese a 7 2 6 Photocell connection en nett nnns sese enne tenen nnne seen 7 27 2545 testet 7 10 Del 10 2 2 C ntrol 11 33 The DEVICE tac te rece ict eee ue het cedes Cet bet E deed ettet aee 12 3 4 The MEASURE 14 3 5 The SYSTEM menu eta e e ttec t eed ete E 14 3 0 The LSENS rere REEL 15 PLEPS m asuremernts 17 4 1 Laser measurements 17 4171 17 4 1 2 IJI characteristic iet 17 ARN Dic E 18 4 1 4 Monitor 18 4 1 5 Modulator 44000 n e e ene ene enn nnne 19 42 Setup the PLS 19 4 2 1 Photoc ell responsivity seoir iaeiaiai 19 42 2 IVEMXBEB maxima erae ter E E OESTE 20
44. ntrol loop stable IVLMXE data available S AVGDAV bit 4216 Control loop stable averaged IVLMXE data available S ERR bit 5232 An error occurred The GPIB SRQ line becomes active when one of the flags enabled with the command is set and remains active until the GPIB controller reads the serial poll status byte Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com PLPS 2005 user manual 29 5 6 Command overview 5 6 1 Set operating mode Command Answer Description Set PLPS mode Valid Always Example K 0 Select the measurement function of the PLPS and switch between remote and local The K command is the only accepted command in local mode can be any of the following numbers Remote control select OFF mode Remote control select Normal mode with a setpoint Remote control select Ramp mode a ramp starts return to Local control do not change mode Remote control do not change mode Remote control select Normal mode 0 Remote control select Reverse mode Exec NB During the ramp no commands are accepted 5 6 2 Read actuals Answer Description Read actual laser current A aa Read actual laser voltage V Read actual light power W Valid Always Example AV 1 5543 Request the actual measured values If the mode is OFF only the AL command returns significant data To gather a
45. ocell current for example by using a larger and or more sensitive photocell of use a smaller optical sphere You can also select a longer Eta measurement time 4 5 4 Bias setting By pressing the BIAS function key you can call up the bias settings These can be altered in both OFF and NORMAL mode In NORMAL mode the changes have direct effect By pressing the function key under ACTUALS you can recall the setpoint actuals screen If the BIAS screen is selected the display shows the setpoints for the photocell bias Lbias the monitor bias Mbias and the modulator bias Xbias 10 01 mA 1 245 V 0 084 mW Lbias 0 04 mA Mbias 10 000 V X 0 0 mA Xbias 0 000 V E ACTUALS BIAS ETA HOLD The photocell bias and the monitor bias are set as high as allowed If the cell has a too high leakage current you are forced to use a lower bias voltage or no bias voltage at all For the photocell a second option is available By selecting the Lbias field and turn the knob fully counterclockwise or by sending a remote set bias command with a negative setpoint you can select the negative input resistance function The display will then show Neg Rin If this function is selected the bias voltage will be equal to 20 the photocell current in Amp re resulting in a virtual negative input resistance of 20 ohms This compensation only works for the three least sensitive ranges 1 10 and 100 mA A
46. oltage can be set between and 5 volt The modulator current is referenced to with on the PLPS the voltage over the modulator diode with Xbias 4 2 Setup the PLPS Before you can measure with the PLPS you will have to setup a number of laser and photocell parameters Incomplete or faulty settings may result in strongly reduced measurement accuracy and or a damaged laser The parameters can be set using the front panel and via the remote interface GPIB or RS232 See for the details the chapters Manual control and Remote control The following settings are applicable Photocell responsivity e Maximum values for laser current and laser voltage light power monitor and modulator current and Eta e Light wavelength e Laser monitor and modulator diode polarity 4 2 1 Photocell responsivity The PLPS gives the light power measured using the external photocell in Watts To do this the photocell responsivity in Amp re per Watt for the wavelength used must be known It is possible to specify the responsivity for a number of wavelengths If the photocell responsivity is not known but you know the light power output of a laser at a known current you can also calculate the responsivity Start with a reasonable guess Usually the responsivity is 0 3 0 5 A W for a silicon cell at 800 nm Measure the light power with the known current look at the deviation and calculate the correct responsivity If you measure us
47. ooks like below Iset 10 00 On the left the actual measured values are given If the bargraph function is enabled you will also see the actual measured value proportional to the maximum value A full bar means that the value has reached its maximum 4 5 1 Changing the setpoint The setpoint can be changed in both OFF and NORMAL mode by turning the knob or giving the appropriate remote commands In NORMAL mode the laser current is adjusted until the setpoint 15 reached If during adjusting a maximum value is exceeded light power monitor current or modulator current then the current will no longer increase When the bargraphs are enabled this is clearly shown by a full bar next to one of the measured values The setpoint can be a laser current light power monitor current or modulator current If you switch to another control parameter then this is already set to the laser measured value for this parameter This allows a smooth switching between different control parameters 4 5 2 HOLD function If you select another control parameter during manual control then the HOLD indicator on the screen appears in reverse video indicating that the HOLD mode is active In HOLD mode the laser current is not adjusted but remains on its present value You can now select a new setpoint parameter and a set a new setpoint After you press the HOLD function key the PLPS will adjust the laser current to reach the new setpoint The HOLD func
48. ou try to settle on a small amount of light it may occur that the IB flag is not always active The DAV flag is set when the measured value almost equals the setpoint In contrast to the IB flag the DAV flag is only cleared after a new setpoint is sent or after the mode changes Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com PLPS 2005 user manual 28 The is set if the DAV flag is set and after the first averaged data is available The flag is cleared together with the DAV flag The RAMPDAV flag is set after completion of a ramp The flag is cleared after reading the last point of the ramp To be precise at the moment the last point is written to the output buffer The flag is also cleared when a new ramp starts The ERR flag follows the error flag in the status word returned by the 25 command The error flag is cleared by reading the error number with the E command The SRQ flag is set if the PLPS sends a GPIB service request see below This flag is cleared automatically at the end of the serial poll 5 5 GPIB service requests The PLPS can activate the SRQ line to indicate that a flag is set in the serial poll status register After powerup this function is not enabled With the command you can force the PLPS to generate a service request when one the following flags 15 set S RAMPDAV bit 224 Ramp data available S DAV bit 328 Co
49. rameter By repeated pressing of the keys you can choose between Lset Mset Xset and Iset The unit of the control parameter will change too the Lset value is in W mW or uW the X and M parameters are set in A mA or uA If you for instance select Lset and set the value to 3 mW the PLPS will adjust the laser current until 3mW light power is measured The bottom row of the screen shows the functions attached to the keys beneath the display The left key is now selected indicating that the actual screen is now showed Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com PLPS 2005 user manual 12 By pressing the key under you will activate the measuring function The function is deactivated by pressing the key again If you select BIAS the Iset value disappears and the Bias values are shown 0 01 0 001 0 003 Lbias 0 00 Mbias 00 Xbias ACTUALS MENU The selected bias voltage in this case Lbias can be adjusted using the knob You can select the monitor or modulator bias voltage by pressing the Tl keys The bias voltages are off in the OFF mode they will be applied if you select NORMAL or only the monitor bias voltage REVERSE By pressing MENU you get access to the menu s The menu s are only available in OFF mode There are four menu screens DEVICE containing the laser specific settings MEASU
50. rantee the specification the PLPS 2005 needs to be re calibrated each year The last calibration date can be checked during powerup Press the left function key under the display during power up the top line of the screen shows Cal followed by the calibration date Calibration can be done by your supplier but it is also possible to do it yourself You will need the following equipment A PLPS 2005 calibrator box e A suitable DMM traceable calibrated and supported by the software e A PC with a National Instruments GPIB card and the PLPS calibration software A detailed description of the procedure and the requirements is found in the calibration manual supplied with the calibrator box and software 7 2 Installing new software The firmware of the PLPS 2005 is stored in Flash ROM This allows you to update the firmware using the serial port PLEASE NOTE updating the PLPS 2005 firmware is not without risks If the procedure fails the PLPS 2005 will not function anymore To load new firmware you need a PC with a terminal program The terminal program needs an ASCII upload function You can use the Hyperterminal program which is supplied with the Windows operating systems The PC must be connected to the PLPS using a so called null modem cable In its simplest form this cable connects two 9 pole D type connectors as following pin 2 to 3 3 to 2 and 5 to 5 Start the terminal program with the following settings 19200 bau
51. ranteed 888 88 SOURCE www artisantg com PLPS 2005 user manual 16 Using the 7 keys you can select a wavelength sensitivity pair By pressing the function key under WL SENS you can toggle between the wavelength and the sensitivity columns The selected value can be changed by rotating the knob In the sensitivity column you can shift the decimal point by pressing the keys The INSERT key adds a new entry to the table with DELETE you can remove entries Up to 40 different wavelength sensitivity couples can be entered If the table contains 7 or more entries you will see the T and or J symbols in the top right and in the bottom right corners These indicators show you that you can scroll up or down to see the rest of the entries Which sensitivity will be used depends on the selected wavelength in the DEVICE menu If you select a wavelength which is not in the list the nearest wavelength sensitivity point will be used Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com PLPS 2005 user manual 17 4 PLPS measurements This chapter describes how to do semiconductor laser measurements with the PLPS 4 1 Laser measurements You can do several laser measurements with the PLPS 2005 The most common measurements will be described below 4 1 1 characteristic Most laser diodes behave electrically like a light emitting diode LED If the current through the d
52. rly query the PLPS status to see if any error occurred This is done using the 25 command If an error occurred you can request the error number and an ASCII error string using the command This command also clears the error flag See also the chapter Error messages for a list with all possible errors 5 4 GPIB serial poll byte The PLPS supports serial polling on the GPIB interface A serial poll is the fastest way to query the PLPS status The serial poll returns an 8 bit status byte You can for example see if new data is available The functions of the single bits are S BUSY bit 0 1 System busy S IB bit 122 Control loop is in band S RAMPDAV bit 224 Ramp data available S DAV bit 328 Control loop stable IVLMXE data available S AVGDAV bit 4 16 Control loop stable averaged IVLMXE data available S ERR bit 5232 An error occurred S SRQ bit 6264 Service request The BUSY flag is set directly after the PLPS 2005 is addressed as listener The flag is cleared after the received command is handled or if an error occurs during command reception The IB flag is active if the control loop is settled that is when the actual laser current monitor current modulator current or light power is nearly equal to the requested setpoint Directly after a new setpoint is given the mode changes or the control loop is disturbed for any reason the IB flag will be cleared NB If the control parameter is noisy for example if y
53. ror during Reading calib Serial Gpib port init or Analog board init is always fatal and points to an internal defect of the PLPS If an error occurs during the test of the analog board a more comprehensive error message appears consisting of an error number and a row of text Such errors can be due to an hardware problem but can also be caused by an expired or wrong calibration For service you can also output a self test report over the RS232 port Press the second function key during power up to generate the report By pressing the fifth function key during power up you will enter the built in front test 6 2 Fatal error messages If the internal hardware guard is activated or if another fatal error occurs the display will show an error message The same message can be read using remote commands After each hardware error you should go to OFF mode first before measurements can be continued The following errors can occur Code Error message Description No error No errors Laser power supply failed The internal power supply fails This points to Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com PLPS 2005 user manual 37 an internal defect Turn off the PLPS immediately and send it to a service center 02 5 the safety switch was open 03 Laser current too high The laser current was too high This problem can be caused by a wiring error or an internal defec
54. rtisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com PLPS 2005 user manual 24 The modulator diode bias voltage can in contrast with the other bias settings be positive as well as negative This allows you to drive the modulator diode in forward direction By varying the modulator bias the amount of light the modulator lets through can be controlled 4 6 RAMP mode Pressing the RAMP key or sending the remote RAMP command starts the automatic ramp The PLPS will do a number of measurements at constant increasing currents The measurement results are stored in memory When the ramp is finished you can read the complete IVLMXE characteristic using remote commands Starting a ramp can be done from OFF mode and from NORMAL mode with a different effect Starting from OFF mode The bias voltages are applied to the photocell the monitor diode and the modulator diode The laser short is removed e The laser driver is turned on with the minimum current The laser diode current is incremented in small steps until the maximum current maximum light or maximum monitor modulator current is reached The IVLMXE measurements are stored per point e After a maximum has been reached the current remains at its present value Starting from NORMAL mode The laser current is incremented in small steps starting at the present current until the maximum current maximum loght or maximum
55. s This is sufficient to protect the laser There are circumstances under which this is not sufficient If the maximum laser current is set too high a 196 step can cause a larger change in light output which can destroy the laser It may not be possible to prevent exceeding the maximum by decreasing the laser current Imagine a shorted monitor diode which will cause a large monitor current To protect the laser and the PLPS against this kind of problems an independent guarding circuit is added The guards will turn off the PLPS when one or more maximum values are exceeded by more than a few percents An error message is shown on the screen and the PLPS must first be switched to OFF mode before you can continue measuring The guard circuit also guards the interlock input and the supply voltages A situation which will occur often in practice is the following the PLPS is switched to NORMAL without a laser diode connected In that case the V guard the guarding for the maximum voltage will immediately turn off the driver because the output voltage exceeds the limt An open current source will give its maximum output voltage The guard reaction time is about 10 microseconds In case of serious overcurrent this will not be sufficient to protect the laser but will avoid damage to the PLPS 4 4 OFF mode After power up the LED indicator in the OFF key is lit and the PLPS is in the OFF mode The OFF mode can be reached from every other mode
56. t 4 Laser voltage too high The voltage over the laser was too high Most 0 likely causes the maximum voltage is set too low or no laser is connected 0 Photocell current too high Photocell current was too high This could be caused by a short in the photocell or wiring or an improper setting of Imax Lmax Lsens Monitor current too high Monitor current was too high This could be caused by a short in the monitor diode wiring problems or improper setting of the Imax Mmax Mbias or M polarity 07 Modulator current too high Modulator current was too high This could be caused by a short in the monitor diode wiring problems or improper setting of the Imax Xmax Xbias or X polarity No photocell responsivity list The PLPS cannot measure without at least one entry in the photocell responsivity table 6 3 Command error messages Error messages due to invalid remote commands are not shown on the display but can only be read via the remote ports The following erros can occur Code Error message Description An unknown command has been given 21 Parameter invalid One or more parameters of the command are invalid 22 Command not allowed here The command given is not allowed in the current mode e g try to set Lmax while the laser is active Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com PLPS 2005 user manual 38 7T Maintenance 7 1 Calibration To gua
57. ta max value is not guarded if the max Eta is exceeded the reading can be faulty The PLPS uses multiple ranges to measure and control the laser monitor modulator and photocell current The range setting is determined using the IVLMXE max settings and will not change while the PLPS is in Normal Ramp of Reverse mode This is done because range switching inevitably causes a jump in the measured value at the moment of switching Consequence of this system is that if the maximum setting is too high a too high range could be selected which results in reduced measurement accuracy Also the Imax setting determines the maximum allowed change in laser current per measurement this change is always limited to 1 of the maximum laser current This means that if the Imax current is set to 100mA the current will be increased with steps of up to 1mA until the desired I L M or X setpoint is reached 4 2 3 Wavelength If the photocell responsivity is specified for different wavelengths you should set the desired wavelength If only one sensitivity is specified in the sensitivity table then this will always be used irrespective of the wavelength setting 4 2 4 Polarities The semiconductor laser the monitor diode and the modulator diode are packaged together Small lasers often have one COMMON connection which is also tied to the package Each diode can be connected with either the cathode or the anode to the common Because the PLPS also has one sing
58. tion can also be used if a possibility exists that the control loop is disturbed by an external process for example if you modulate an external current on the laser current Artisan Technology Group Quality Instrumentation Guaranteed 888 88 SOURCE www artisantg com PLPS 2005 user manual 23 By pressing hold the control loop will not try to compensate the external modulation 4 5 3 ETA function The Eta measurement function can be activated and de activated by pressing the function key under the Eta indicator or by sending the remote Eta enable command When the Eta measurement function is active a small 5 KHz AC current is superposed on the laser current The 5 AC component of the photocell current is measured and the ratio between the light power and the superposed current is displayed The Eta function is active only when the control loop is settled If the setpoint is altered no Eta measurements are taken until the new setpoint is reached If the control loop can t settle for example if the light power is the control parameter and measurements with very small light power levels are done the Eta function cannot be used The display will then show Because the Eta modulation current the superposed AC current is only a fraction of the laser current the Eta measurements in the most sensitive light ranges less than 100uA photocell current will be relatively noisy In that case try to provide for more phot
59. tting data e String termination The ASCII messages will be delimited with nothing a linefeed a carriage return or both a linefeed and a carriage return LCD contrast The LCD contrast depends on the environment temperature and the viewing angle With this setting you can optimize it LCD brightness You can turn off the LCD backlight and dim the other indicators e Bar graphs This function enables the bar graphs next to the measured IVLMX values in the normal screen giving a fast visual overview of these values The length of the bar graph is determined by the maximum values as setup in the DEVICE menu If Imax is set to 40mA the bar will be fully on at 40mA 3 6 The LSENS menu The PLPS measures the current through the external photocell and converts it directly to light power in Watts To do this you must specify the photocell sensitivity in Amp per Watt for the wavelength used The LSENS menu contains a table with the sensitivity for one or more wavelengths You select the LSENS screen by pressing the OFF key then MENU and then LSENS The screen looks like this 0 303 A W 0 320 A W 0 124 The left column shows the wavelengths the right column shows the sensitivities belonging to the wavelengths on the left You can leave this screen by pressing OFF or MAIN Each time you leave this screen the entries will be sorted on wavelength Artisan Technology Group Quality Instrumentation Gua

Muetta PLPS 2005 Manual

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