Wavellength User Manual - Sacher Lasertechnik Group
Contents
1. v4 05 9 9 e 595 72 4 7 Bs u L 3 AP DC Level of 2E 1 Desired Peak Figure 7 Absorption Peak DC Level Operation and Maintenance Manual 5302WL Wavelength Locker Unit 16 Version 1 0 Sacher Lasertechnik P 6 The next step is to adjust the Wavelength Locker phase The PZT and Current phase needs to be adjusted before attempt to lock the External Cavity output It is important to adjust the phase of both dither signals looking at the photodetector signal at the bottom of the absorption peak The PZT and Current reference signal are located in the rear of the Wavelength locker Connect the Reference Signal output to the oscilloscope Channel B input On the oscilloscope change the trigger to Channel B The Ref Select switch in the rear of the Locker determines which reference signal is applied to the Reference Signal output Switch the Ref Select switch to PZT On the Wavelength Locker turn up the amplitude of the PZT dither signal The dither signal will appear on the photodetector signal The PZT dither signal will be in synch with the reference signal You may need to tune the PZT of the ECDL a little to find the desired line At the absorption peak the photodetector signal will be a 2 times the dither signal If the photodetector signal 1s not at 2f of the dither adjust the Bias on the Wavelength Locker Fig A2 in the appendix shows the Doppler free equiv2. Figure 2 is a block diagram of the Wavelength Locker system The figure is followed by a description of Wavelength Locker internal circuitry Figure 2 Model 5302WL Block Diagram Sacher Lasertechnik P Operation and Maintenance Manual 5302WL Wavelength Locker Unit Version 1 0 Input Signal The input signal to the 5302WL is generated from external photo detector The photo detector circuitry converts the optical signal from a reference cell or temperature controlled etalon to an electrical signal for the Locker The photo detector amplifier output 1s connected to the Locker s Input Amplifier by the front panel Input connector The Input Amplifier filters and amplifies the input signal The output of the Input Amplifier is directed to the Meter Rotary Switch allowing the DC component of the Input Amplifier output to be displayed on the Front Panel Display The Zero Adjust potentiometer on the front panel is used to null the Input Amplifier output The Input Amplifier output is also directed to the overload detector which will illuminate a front panel OVR LED if the output of the input amplifier exceeds the allowable 10volt limits The sum of the peak input voltage plus the offset voltage must not exceed 10 volts The phase and polarity of the Input Amplifier output may be reversed with the Switch This switch is usually used to obtain an overall negative feedback in the control loop Bo
3. ta Sen Pique He Figure 18 Equivalent to fig 8 T Los sor nee M Pos Aldus ERFASSUNG TTT Ts d EEESIEE pitzenaeii prmmcmma mo m CHT SWR EE UP MED 7 OUR WW Fi Ire HE iJ Figure 19 Equivalent to fig 14 Operation and Maintenance Manual 5302WL Wavelength Locker Unit Version 1 0 Appendix 32 Sacher Lasertechnik Appendix 1 Bv do not overcharge BNC ON OFF output ESSO Pet Poti PD PTEN L d LLL i KR Interior of the Saturated Absorption Spectroscopy Setup Fig 1 Stabilisation Setup BS polarizing beamsplitter L 4 quaterwaveplate PD1 photodiode 1 of balanced receiver PD2 photodiode 2 of balanced receiver Pot amplifies the difference of the signal from PD1 and PD2 adjusting the difference is done by Poti max ImW input Figure 20 Doppler free saturated absorption spectroscopy setup Note Batteries with a lifetime of several hours are included You may use rechargeable batteries and charge them with the 18V connector if needed There are no overcharge security so DO NOT ACCIDENTLY OVERCHARGE While measuring the batteries must not be charged Operation and Maintenance Manual 5302WL Wavelength Locker Unit 33 Version 1 0 http www sacher laser com Company Profile Sather Lasertechnik is leading manufacturer of tunable external cavity diode lasers ECDL with more than 10 years of experience The product range Includes ant
4. are displayed Note the DC voltage level at the bottom of the absorption peak You may also use AC if DC is not possible In this case use the fluorescence of the hyperfine lines to detect the desired peak you want to lock at Also the PZT ramp may be chosen smaller if you use the smaller Doppler free signals or equivalent small peaks Absorption Feature S P pu E Te gf ftttstsosssatestitittitoro I j 2 gt DC Level of Desired Peak Figure 6 Rb Absorption Feature Note A figure of a Doppler free saturated absorption feature 1s shown in Fig 16 in the Appendix Operation and Maintenance Manual 5302WL Wavelength Locker Unit 15 Version 1 0 Sacher Lasertechnik P 5 On the Wavelength Locker turn off the Feedforward switch Using the PZT adjust of the External Cavity Laser adjust the PZT voltage until the oscilloscope level is at the level of the bottom of the absorption peak or desired hyperfine peak With the detector output at the bottom of the peak switch the meter select on the Wavelength Locker to Input Use the Zero to adjust the photodetector DC level to approximately zero Note the voltage reading of the Locker display Any change in the input DC level will indicate that the system has drifted off or to the side of the absorption peak Note the input display DC level if possible E33 E ri Ni MW 9198083090 pesaus 00090 PO POM 0 96980 labaina etos E bo 9 os
5. dc voltage on the oscilloscope Switch the panel meter to input and adjust the INPUT ZERO so that the meter reads 00 0 when the dc level of the signal on the oscilloscope is near the desired lock point Gradually turn up the gain while watching the signal on the oscilloscope If the lock point moves away from the desired dc level then compensate by changing the PZT BIAS Turn the PZT GAIN slowly up until the loop begins to oscillate and then turn the gain lower to establish the gain needed for stable operation The position of the lock point may be finely adjusted by changing the PZT BIAS Turning the PZT GAIN to the off position may lock onto the other side of an absorption feature The polarity switch is changed to opposite position Then find the lock point by adjusting the PZT BIAS and slowly turn up the gain as described in step 4 After the PZT lock is stabilized the current lock gain may be increased to reduce the frequency noise of the laser over a greater Operation and Maintenance Manual 5302WL Wavelength Locker Unit 25 Version 1 0 Sacher Lasertechnik P bandwidth Turn the gain up slowly until the loop starts to oscillate Then back off the gain so the loop is stable Reducing the frequency noise of the laser through current feedback will correspondingly increase the amplitude noise of the laser Note If the current loop does not reduce the high frequency noise then the polarity of the curr
6. if purchased or use equivalent equipment On optical table align cavity output so that pass thru reference cell or temperature controller Insert beam splitter or neutral density filter between laser output beam and cell If a neutral density filter is used adjust so that the laser power going thru the cell is less than ImW Align the photodetector so that the laser beam is positioned at the center of the detectors active region The detector transimpedance amplifier output is connected to the input of the lockbox and oscilloscope Channel A Adjust the neutral density filter so that the transimpedance amp is not saturated Also refer to the Users Manual of the RB Setup if purchased and the references therein Operation and Maintenance Manual 5302WL Wavelength Locker Unit 13 Version 1 0 Sacher Lasertechnik P OPTICAL SETUP eee ei i i i i i i i i i i i i i i ee ee X eee eee ee i i i i i i i i i ee ee Reference Cell Orb Etalon ECDL Pilot PC QUEEN front side g gt e e e 2 a Figure 5 External Cavity Wavelength Locking Setup Cable Description Connect to Pilot PC Laser and TEC cable Laser and TEC connector PZ MOD IN connector 1 Feedforward Trigger Signal MOD IN Table 1 Optical Setup Connection Table If there is no oscilloscope connected to the Piezo out a eround connection from the piezo Output to the ground is necessary N
7. the circuit card and the front panel Control signals are sent from the mechanical switches and potentiometers on the front panel Described below are the functions of each of the controls for the Model 5302WL front panel Triad Technology 5302 Wavelength Locker Figure 3 Model 5302WL Front Panel Operation and Maintenance Manual 5302WL Wavelength Locker Unit 6 Version 1 0 Sacher Lasertechnik P Potentiometers PZT Channel Gain Current Channel Gain PZT Dither Amplitude PZT Dither Phase Current Dither Amplitude Current Dither Phase Input Zero Adjust Output Bias Control 2 Switches Dither Sidelock Polarity Feedforward Meter Select 3 Connectors Input Signal PZT Output Current Output Feedforward Input Operation and Maintenance Manual 5302WL Wavelength Locker Unit Version 1 0 Adjustable from zero to ten Adjustable from zero to ten Adjustable from zero to 100 millivolts peak to peak Adjustable from zero to 180 degrees Adjustable from zero to 3 volt peak to peak Adjustable from zero to 180 degrees Offsets Photodetector signal by up to 10 VDC Offsets output signal by up to 10 VDC Switch for setting the mode to either peak lock or sidelock operation The polarity reversal switch changes the polarity of the input signal by 180 degrees Note that the input bias reverses along with the signal The bias voltage may be varied from full scale positive to full
8. 765 Equador Way Buena Park CA 90620 USA Tel 1 800 352 3639 Fax 1 714 670 7662 Support sacher laser com Operation and Maintenance Manual 5302WL Wavelength Locker Unit 0 Version 1 5 Sacher Lasertechnik P Content General Information 1 IMEFOOUCHOM ns i ta RO Ee TAIN CEN Sa OUS l Theory of Operatii essorer nrn ER E ESER 2 Safety Terms and Symbols eeeeeeuussss 5 General Warnings and Cautions 5 System Operation 6 liringoreiproinro T 6 General ODerdtlOT co aee dite os eu d Dt ss edu eels 11 Ordering Information 27 Wavelength Locker Model 5302WL 21 opecifications 28 Wavelength Locker Model 5302WL Specifications 28 Factory Service 30 Inirod t uro 30 CJD CAINS Set VICO doct etetaaso pter vont suapte ane det ae cagias 30 Appendix 31 StabIDZAttor PICDEe S pen a ease 3l Operation and Maintenance Manual 5302WL Wavelength Locker Unit 0 Version 1 5 Sacher Lasertechnik List of Figures Fisure L Model 3502 WL Wavelengih LOCKe s eius uei E E E TS l Figure 2 Model 5302 WL Block DiagiaMs xiii A don as a a a aes 2 Fieure 2 Model 2302WL Front Pane besre a O 6 Figure 4 Model OWE Rear Pane 2 br A OS 9 Figure 5 External Cavity Wavelength Locking Setup eese 14 Pioure 6 RD ADSOPD UOD PedUfe 2 tr te bI ERO Yd S earn nck Maus pte Ad odds du ues 15 Picure 7 Absotplion Peak DC Wey Cl
9. Arendt Str 3 7 35037 Marburg Germany Tel 49 6421 305 0 Fax 49 6421 305 299 Contact sacher laser com or Triad Technology at 720 494 0717 Please have the following information available 1 Instrument model number On front panel 2 Instrument serial number On rear panel 3 Description of the problem If the instrument is to be returned Sacher Lasertechnik or Triad Technology you will be given a Return Materials Authorization RMA number which you should reference in your shipping documents as well as clearly marked on the outside of the shipping container Operation and Maintenance Manual 5302WL Wavelength Locker Unit 30 Version 1 0 y Group Sacher Lasertechni Appendix Appendix Stabilization Pictures This appendix shows the peaklock in case of using a Doppler free saturated absorption spectroscopy setup The spectroscopic setup is shown in the last figure j Tek JL e Sup n M Pon ALus cH 1 invertiaruma 1 aus CHT imeach J mVig M Sto EH ee igure HA Figure 16 Lamb dips of Rb ERFASSUNG Namal ADT ast Mittelwer te CHT miam T0 y MiERS ee Figure 17 Resolved Lamb Dip without Doppler background Operation and Maintenance Manual 5302WL Wavelength Locker Unit 3l Version 1 0 Sacher Lasertechnik e 1 STE M Pos 4 us ERFASSUND Ji NUN Normale ALS TUT Mitzelwerre E i 4 4 4 CH ima 1000 Mosus 95
10. Table 4 Power Supply Specifications ouo iiti bot on ninine Qu Iait en ibot em Mtem bati quate 20 Operation and Maintenance Manual 5302WL Wavelength Locker Unit Version 1 0 Sacher Lasertechnik P General Information Introduction This manual describes the features and specifications of the Wavelength Locker Model 5302WL instrument The Wavelength Locker is design to stabilize the wavelength output of an external cavity laser diode system The Wavelength Locker is compatible with both Littrow and Littman Metcalf configured external cavity systems The frequency locking detection device can be either a reference cell or temperature controller etalon The Wavelength Locker instrument is supplied with an external power supply T TL n j Boe Figure 1 Model 5302WL Wavelength Locker Operation and Maintenance Manual 5302WL Wavelength Locker Unit l Version 1 0 Sacher Lasertechnik P Theory of Operation Operation and Maintenance Manual 5302WL Wavelength Locker Unit Version 1 0 The Wavelength Locker 5302WL is design to stabilize the output wavelength of an External Cavity Laser Diode System by using either a dither lock or a sidelock mechanism The dither locking mechanism uses a modulator demodulator combination for centering the External Cavity output on the peak of a reference feature The sidelock mechanism provides an un modulated operation for locking the laser s wavelength along the side of the reference feature
11. al from the gain amplifier output and modulation Dither signal The PZT channel also has gain amplifier and modulation Dither signals to the summing amplifier but also has a DC offset voltage from the front panel Output Bias potentiometer and an external Feed Forward voltage from the Feed Forward BNC connector The output voltage of the PZT summing amplifier is monitored by the meter via the meter selector switch and by the Overload Detector circuit The front panel OVL lamp will illuminate if the PZT summing amplifier output exceeds the allowable 10volt limits Dither Signals The Wavelength Locker generates two dither signals PZT and Current The PZT dither frequency is 800 hertz There are two Wavelength Locker versions of current dither frequencies IMHertz and 100KHertz The dither signal amplitude and phase are adjusted by two concentric potentiometers on the Locker front panel The Amplitude and Phase 0 potentiometers set the amplitude and phase for each of the dither signals The outside potentiometer controls the amplitude and the inner potentiometer is used for the phase adjustment The dither amplitude is adjustable between zero and a maximum of I00millivolts peak to peak for the PZT channel and between zero and 3volt peak to peak for the current channel The phase potentiometer sets the phase relationship between the internal reference signal and input signal over a 180 degrees range The Front Panel display via the me
12. alent The Locker display should be reading zero for the input DC level when the system is at the absorption peak As you adjust the PZT phase 6 the photodetector signal moves in phase compared to the reference signal The phase is adjusted properly when photodetector signal forms an S curve is center of the positive half of the reference signal With the PZT phase properly adjusted change the Wavelength Locker meter select to PZT 6 read the phase value Turn the PZT dither signal amplitude back to zero Change the Wavelength Locker meter select to Input The Locker display should read zero Figure 8 shows the proper phase relationship between the reference output and photodetector signal v m a A 3333417331571 111 PRU PERT EET fie Figure 8 PZT Phase Adjust Note Fig 18 in the appendix shows the Doppler free equivalent Operation and Maintenance Manual 5302WL Wavelength Locker Unit 17 Version 1 0 Sacher Lasertechnik P Operation and Maintenance Manual 5302WL Wavelength Locker Unit Version 1 0 7 After adjusting the PZT phase the Current phase is adjusted next a EEF to 2222 bs Switch the Ref Select switch in the rear of the Locker to Current On the Wavelength Locker turn up the amplitude of the Current dither signal The dither signal will appear on the photodetector signal The Current dither signal will be in synch with the reference signal At the absorption peak the photodetector signal w
13. donc dodo E to tesi pt dedi 16 Fene See PZ PASS PNG USE sare etate tae denm ide eta tute cnn etaim 17 PIO ure 9 Current Phase Ad US e E OEO EE LONN 18 Figure 10 PZT Modulation Signal along Absorption Peak ccccccccccssseeeeeeceeeeeeeeeeeeees 19 Figure 11 PZT Modulation Signal on the side of the Absorption Peak 20 Figure 12 PZT Modulation Signal at the bottom of the Absorption Peak 21 Fisure 15 Current Lock Mechanic 2i oa ias diet asi N MR oa bid datas quU Rd ied Mat des 22 Figure 14 Current Modulation Signal eese eene 22 Figure 15 Current Locked to Absorption Feature eeeeeesessessessssseeeeeeeeeeee nenne 24 Foure TO L nmb dips OP RD uice eene EU REDE E bue b ME Runner Scb diu etu eee ale 3l Figure 17 Resolved Lamb Dip without Doppler background eeeeeeessssss 3l Figure 13 gt Equivalent to T9 Snesere eri U m Oeo a EU N ERE CUORE RI CTI oa ecu EE UE 32 FEisure d9 Equivalent 10 No 4s Liuius o te poro dto eoe Drei aeo ata E Eg tog eta tare Pigque 32 Figure 20 Doppler free saturated absorption spectroscopy setup esses 33 List of Tables Table l Optical Setup Connection Table ia or is Rankin eb Re ven aate R ek vetus 14 Table 2 Part Number Tor Model S502 W Derris ena eaa 27 Table 5 Wavelength Locker Specifications 2 Auto toL titor icta ee ier eas 28
14. ent loop relative to the PZT loop will need to be reversed The unit is preset at the factory Please contact Triad Technology concerning information for modifications to your Wavelength Locker unit Operation and Maintenance Manual 5302WL Wavelength Locker Unit 26 Version 1 0 Sacher Lasertechnik Group Ordering Information Wavelength Locker Model 5302WL Model TT 5302WL 1M US TT 5302WL 1M AS TT 5302WL 1M EU TT 5302WL 100K US TT 5302WL 100K AS TT 5302WL 100K EU Description Wavelength Locker with US compatible AC power cord Wavelength Locker with Asian compatible AC power cord Wavelength Locker with European compatible AC power cord Wavelength Locker with US compatible AC power cord Wavelength Locker with Asian compatible AC power cord Wavelength Locker with European compatible AC power cord Table 2 Part Number for Model 5302WL Operation and Maintenance Manual 5302WL Wavelength Locker Unit Version 1 0 Appendix 27 Sacher Lasertechnik P Appendix Specifications Wavelength Locker Model 5302WL Specifications Model 5302WL Specifications Input Signal Range 1 to 10volts Input Signal Zero t 10volts PZT Dither Frequency 800Hertz Current Dither Model 1M 1MHertz Model 1K 1KHertz Frequency PZT Amplitude Adjust 0 to 100millivolts peak to peak Current Amplitude 0 to 3volts peak to peak Adjust PZT Phase Adjust 180 degrees Current Phase Adjust 180 degrees PZT O
15. ill be a 2 times the dither signal If the photodetector signal is not at 2f of the dither adjust the Bias on the Wavelength Locker The Locker display should be reading zero for the input DC level when the system is at the absorption peak As you adjust the Current phase 6 the photodetector signal moves in phase compared to the reference signal The phase is adjusted properly when photodetector signal forms an S curve is center of the positive half of the reference signal With the Current phase properly adjusted change the Wavelength Locker meter select to Current 0 read the phase value Turn the Current dither signal amplitude back to zero Figure 9 shows the proper phase relationship between the reference output and photodetector signal PEER EER 3 3 Pob Eod dot EP E Pot t bo d 381241439 0t ER EE HH iid Figure 9 Current Phase Adjust 18 Sacher Lasertechnik P Operation and Maintenance Manual 5302WL Wavelength Locker Unit Version 1 0 PZT Lock Procedure The PZT is locked to the absorption peak first Switch the Ref Select switch back to PZT and trigger on this signal again Turn up the amplitude of the PZT dither signal until the signal is present on the photodetector output Different levels of the absorption feature can be identified by adjusting the PZT DC voltage of the External Cavity Laser or by using the Bias and observing the amplitude of the PZT dither signal At the base of the absorptio
16. it card and the front panel Control signals are sent from the mechanical switches and potentiometers on the front panel Described below are the functions of each of the controls and outputs for the Model 5302WL rear panel PZT CURRENT D C INPUT REF OUTPUT AONE Figure 4 Model 5302WL Rear Panel Sacher Lasertechnik P 1 Switches Power Power switch for turning the unit Off and On Ref Select Select either PZT or current reference output 2 Connectors Ref Output Wavelength Locker internal frequency reference signal TTL compatible output DC Input Power input connection for the Wavelength Locker Operation and Maintenance Manual 5302WL Wavelength Locker Unit 10 Version 1 0 Sacher Lasertechnik P General Operation Please read and understand through this general operation example at least one time before following the steps This will make your start much easier The Wavelength Locker does not require any warm up time The 5302WL control signals are applied to both the piezoelectric actuator PZT in the external cavity tuning mechanism for DC and low frequencies and laser diode current driver for higher frequencies for rapid high frequency disturbances The PZT servo channel will be effective from DC to about 800Hz hertz while the current servo channel will be effective from about 800Hz hertz to 1 MHz or 100Khertz dependent on the Wavelength Locker model The PZT and current channel t
17. kwise to the OFF position for both the PZT and CURRENT Switch meter select to PZT using the PZT o potentiometer adjust for zero phase Switch meter select to CURRENT using the current 0 potentiometer adjust for zero phase b Switch the meter select to OUTPUT adjust to zero voltage using the BIAS adjust potentiometer Turn off the GAIN on both PZT and CURRENT Switch the FEEDFORWARD to OFF position Set the 5302WL to Peak Lock and polarity Set to polarity may be needed in case the absorption is inverted by the balanced receiver Switch the meter select to INPUT adjust to zero voltage using the ZERO adjust potentiometer 2 Frequency Generator setting are as follows c Frequency adjust 50Hz or 100Hz and amplitude and amplitude adjusted to 1 volt peak to peak The output signal should be set to a ramp with 50 duty cycle with zero DC offset if possible not needed if the PI 1000 RG with external ramp access is purchased Adjust the oscilloscope to get the ramp to extend the across the display with zero volts in the middle of the screen d Connect the output of the Function Generator OUTPUT to the Oscilloscope TRIGGER input and 5302WL FEEDFORWARD input 12 Sacher Lasertechnik P 3 Set up Lockbox per Figure 5 to the following e Connect the PZT and CURRENT outputs of the 5302WL to External Cavity Laser PZT PI 1000 PZ and CURRENT PI 1000 MD modulation inputs
18. n feature the dither signal is a relatively small in amplitude The feature baseline will not have much of a slope As the PZT voltage is adjusted along the side of the absorption peak the amplitude of the dither signal will increase dependent on the slope of the peak s side At the bottom of the absorption feature the photodetector output will decrease in amplitude but the frequency will be double the dither signal frequency Figure 10 illustrated the change in PZT dither signal as the laser output transverses the absorption feature Error Signal oO Oe nO An an AAT X WV VV AAAA UV VV AAA VAV V V 7 VE Ve ASN Dither Signal Absorption Feature A IN JN LN Figure 10 PZT Modulation Signal along Absorption Peak 19 Sacher Lasertechnik P 8 On the Wavelength Locker turn the PZT amplitude adjust to about 1 3 of it full range The PZT dither signal will appear on the oscilloscope photodetector signal Figure 11 shows the photodetector dither signal along the side of the absorption peak k Pob P POP P bob opob Pob ok bod o EER EE 3 x E amp d EET EE d d d Poi p ok Pod od i Figure 11 PZT Modulation Signal on the side of the Absorption Peak Operation and Maintenance Manual 5302WL Wavelength Locker Unit 20 Version 1 0 Sacher Lasertechnik P 9 Adjust the Bias knob until the meter display reads the absorption peak DC level The oscilloscope s sine wave will be twice the PZT dither f
19. oacher Lasertechnik Group T ET T IT A ia dan r pale y Wavelength Locker Unit Top Of Line Stabilization Operation and Maintenance Manual ntto AwwwW sacher laser com Sacher Lasertechnik P Warranty A This Sacher Lasertechnik product is warranted against defects in materials and workmanship for a period of one year from date of shipment Duration and conditions of warranty for this product may be superceded when the product is integrated into becomes a part of other Sacher Sacher Lasertechnik products During the warranty period Sacher Lasertechnik will at its option either repair or replace products which prove to be defective The warranty period begins on the date of delivery or on the date of installation if installed by Sacher Lasertechnik P This warranty is in lieu of all other guarantees expressed or implied and does not cover incidental or consequential loss Copyright 2004 Sacher Lasertechnik All rights reserved Service Information and advice about the performance or operation of Sacher Lasertechnik products is available from our web site and our applications engineers For quickest response ask for Technical Support and have your model and serial number available Support is available by Sacher Lasertechnik P Hannah Arendt Str 3 7 35037 Marburg Germany Tel 49 6421 305 0 Fax 49 6421 305 299 Contact sacher laser com or 5
20. ogether form a control loop with a response over the range of both control loops Input Power Connector The Wavelength Locker is supplied with an external power supply The external supply is compact in size and is supplied with a universal input capable of an input voltage range from 90 to 260volts The power supply is connected to the Wavelength Locker thru a five 5 pin DIN connector The AC input connector is an IEC320 C13 connector The user can order the 5302WI Wavelength Locker with a different power cords Operation and Maintenance Manual 5302WL Wavelength Locker Unit 11 Version 1 0 Sacher Lasertechnik P Operation and Maintenance Manual 5302WL Wavelength Locker Unit Version 1 0 Warm Up and Environmental Consideration The 5302WL Wavelength Locker does not have a warm up and can be used immediately after being powered on The External Cavity laser system may have a warm up time To achieve best performance allow the recommended warm up for External Cavity Laser system as described in the User s Manual for your laser Allowing for the laser system warm up will make for a more stable frequency lock Consult the laser system s user manual to determine the proper warm up time Wavelength Locker Initial Setup With the 5302WL connected to its power supply push the power switch to supply power to the Locker The front panel display will light up 1 Initial 5302WL settings are as follows a Turn amplitude countercloc
21. ote This setup is realized with the Sacher Lasertechnik PILOT PC laserdriver with a piezo option If you get a PILOT PC laserdriver from us the piezo option will be installed so that you can plug the BNC to the 5302WL directly Operation and Maintenance Manual 5302WL Wavelength Locker Unit 14 Version 1 0 Sacher Lasertechnik P Peak Lock Procedure The following example involves locking the output of a 780nm External Cavity laser to a natural Rubidium reference cell The wavelength of the External Cavity laser needs to be set to 780 2nm The External Cavity User Manual will provide instruction for setting the output wavelength If purchased the Rb Setup User s Manual will provide further details 4 Set up the oscilloscope to display the photodetector signal on Channel A and Frequency generator ramp output on Channel B Adjust the Frequency Generator so that positive edge of the ramp 1s approximately the length of the oscilloscope display On the Wavelength Locker switch the Feedforward switch to On On oscilloscope you should see the absorption feature If you do not see the desired peak adjust the External cavity PZT voltage until the peak is displayed on the oscilloscope display Adjust the PZT voltage until you see the absorption centered of the oscilloscope display The oscilloscope measures the DC level of the desired peak Figure 6 shows the absorption feature of a natural Rubidium cell and the signal generator ramp
22. quency is produced by the phase difference between the internal reference frequency and the dither signal at the photodetector The beat frequency approaches DC as photodetector signal frequency approaches the Wavelength Locker internal reference frequency Adjusting the gain to minimize the beat frequency locks the current loop Figure 13 illustrates the current locking mechanism I AAAARIAVAAARAAAA ANNAAAAAARAAAAAA ar AAA VIVA au Uu Vv ENUN Operation and Maintenance Manual 5302WL Wavelength Locker Unit Version 1 0 AAN L AA Locked Figure 13 Current Lock Mechanism Current 22 Sacher Lasertechnik P 10 Turn up the Current dither amplitude until the dither signal appears on the photodetector signal Figure 14 shows the photodetector signal with the current dither amplitude increased Figure 14 Current Modulation Signal 11 Start increasing the Wavelength Locker current gain potentiometer As the gain is increased the amplitude of the photodetector sine wave will decrease and become try to become flat The photodetector signal will start to oscillate when there is too much gain Turn down the gain until a stable signal is achieved To optimize either of the loops you can decrease the amplitude and increase the gain until you have the loop locked with the minimum input voltage swing Fig 15 shows final Current lock Operation and Maintenance Manual 5302WL Wavelength Locker Unit 23 Version 1 0 Group Sacher La
23. refiecHon coated diode lasers ECDis in Littrew and In Littman Metcalf configuration as well zs driver electronics for diode lasers and sophisticated maasuring eipctroniers Sacher Lasertechnik was founded as a spin off compary cf Marburg University In 1992 We started up with the manufacturing of anthrefiection coatings for diode lasers according to patent 6 297 066 Based on this key knowledge we developed stable narrow linewidth wavelength tunable laser sources for spectroscopy patent 5 867 512 We gratefully acknowledge the support of the German ministry of research within contracts 1386653 and 137156 Qur product range currently covers Diode Lasers Fabry Perot DFB Antirefiection coated Tunatte diode lasers in Littrow configuration Tunable diode tasers in Littman Metcalf configuration High power P gt 300m Raman lasers in Littrow configuration Low nabe dioda laser controllars Measurment electronics Please contact us with your measurement requirements We would be proud Do NESCIT ANC MI ES JUS Sacher Lasertechnik LLC Sacher Lasertechnik GmbH 5765 Equador Way Hannah Arend Str 3 7 Buena Park CA 90620 35037 Marburg U S A Germany www sacher us www sacher de
24. requency Figure 12 shows the photodetector dither signal along the bottom of the absorption peak Start increasing the Wavelength Locker PZT gain potentiometer As the gain is increased the amplitude of the photodetector sine wave will decrease slightly and produce 2F photodetector signal The photodetector signal will start to oscillate when there is too much gain Turn down the gain until a stable signal is achieved Fig 12 shows PZT modulation with 2f at bottom of absorption peak Small changes of the PZT on the laserdriver of the ECDL will not result in a wavelength change anymore which means the laser is locked please carefully check In case the laser is not locked the polarity switch may be in the wrong position fidi tititik Pot bot Por do bo b Pot ERE E haad we PE fiid id REE Figure 12 PZT Modulation Signal at the bottom of the Absorption Peak Operation and Maintenance Manual 5302WL Wavelength Locker Unit 2 Version 1 0 Sacher Lasertechnik P Optionally Current Lock Instructions The current Icok may be purchased optionally and is normally not installed or tested With the PZT loop locked the Current loop will need to be adjusted for locking The current locking mechanism at the absorption peak is accomplished when the current dither signal and the photodetector signal are brought in phase When the current dither is applied to the photodetector a beat frequency is present The beat fre
25. scale negative This switch allows an external signal source to be added to the PZT output signal In the OFF position the switch simply grounds the unused input to the output amplifier when Feedforward is not used This switch selects one of four measurements to display on front panel Input signal from an external peak detection circuitry Connects to the PZT modulation input of the laser system Connects to the Current modulation input of the laser system An external signal used to modulate the PZT via the front panel Feedforward BNC connector Sacher Lasertechnik P 4 Display Indicator Meter Overload Indicators The digital panel meter displays the DC level of the input error signal the DC output level of the PZT output the PZT dither phase or the Current dither phase If the output of the input amplifier or the PZT output amplifier exceeds allowable limits the indicators will illuminate It will extinguish when the voltage overload is gone Operation and Maintenance Manual 5302WL Wavelength Locker Unit Version 1 0 Sacher Lasertechnik P Operation and Maintenance Manual 5302WL Wavelength Locker Unit Version 1 0 Model 5302WL Rear Panel The Wavelength Locker controls are designed to make the unit a highly flexible accessory to an External Cavity Tunable Laser System The controls mounted on the front panel are indirect that is the actual signals are not routed back and forth between the circu
26. sertechnik Figure 15 Current Locked to Absorption Feature Note Fig A4 in the appendix shows the Doppler free equivalent Operation and Maintenance Manual 5302WL Wavelength Locker Unit Version 1 0 24 Sacher Lasertechnik P Sidelock Procedure The sidelock procedure may not be installed if not purchased The sidelock allows the laser to be locked on either side of an atomic or molecular absorption line or an etalon transmission line The method of locking to the side of a transition is to define a point on the side of the transition that will give a zero volt error signal If the frequency of the laser deviates from the set point the resulting error signal sign is such that it pushes the laser frequency back to the set point Setup the Wavelength Locker as shown in Fig 5 with the CURRENT and PZT GAIN in the off position 1 The signal generator going into the FEED FWD should be a 50 Hz sine wave to produce the cleanest features Use dc coupling on the oscilloscope and trigger off the pulsed output of the frequency generator Gradually decrease the amplitude from the signal generator and adjust the PZT voltage on the External Cavity laser until only the line observable 1s the feature to lock onto Record the peak to peak voltage of the full feature and the voltage of the lock point on the oscilloscope Turn off the FEED FWD and use the Wavelength Locker BIAS potentiometer to locate the desired lock point by noting the
27. ter selector switch monitors the phase for the PZT and current dither signals Product Features Flexible User Interface Dual Frequency Peak Locking using both PZT and Current Compatible with External Cavity Tunable Diode System not purchased features may not be installed Sacher Lasertechnik P oafety Terms and Symbols The following safety terms are used in this manual e The WARNING heading in this manual explains dangers that could result in personal injury or death e The CAUTION heading in this manual explains hazards that could damage the instrument e n addition a NOTES heading gives information to the user that may be beneficial when using this instrument General Warnings and Cautions The following general warning and cautions are applicable to this instrument Operation and Maintenance Manual 5302WL Wavelength Locker Unit 5 Version 1 0 Sacher Lasertechnik P System Operation Introduction This section of the manual provides the operational instruction for the 5302WL Wavelength Locker Module The user should read this manual carefully before attempting to use this instrument Only purchased features will be installed Model 5302 Front Panel The Wavelength Locker front panel controls are designed to make it a highly flexible accessory to an External Cavity Tunable Laser System The controls mounted on the front panel are indirect that is the actual signals are not routed back and forth between
28. th the DC bias and the signal are reversed simultaneously with the front panel Polarity switch Dither Sidelock Mode The output of the Polarity switch is routed through the Dither Sidelock Selector Switch In the Sidelock mode the switch bypasses the demodulators and precludes the application of the modulating dither signals to the PZT and current output drivers while in the sidelock mode There is only a gain adjustment provided in the sidelock mode In the Dither mode the modulating dither signals are routed to the PZT and current output drivers The output signal from an external photodetetor is applied to the individual demodulators for PZT and Current loops Gain Amplifier After the demodulator there is a gain amplifier for PZT and current respectively The gain amplifier has an output gain that varies between zero and ten The variable gain amplifier 1s set from the Locker front panel Each of the amplifier s gain 1s controlled from the PZT Gain or Current Gain potentiometer respectively The PZT and Current Gain potentiometers should be rotated counterclockwise to there OFF positions The OFF position of the Gain potentiometers indicate a gain of zero Sacher Lasertechnik P Operation and Maintenance Manual 5302WL Wavelength Locker Unit Version 1 0 Output Stage and Driver In both channels there are output summing amplifiers In the Current channel there are two inputs to the summing amplifier the sign
29. utput Bias Adjust 10volts Power Requirements see Table 2 Power Supply Specifications Weight 0 75 Lbs 1 65 Kg Size H x W x D 3 5 in x 8 5 in x 11 in 88 mm x 215 mm x 280 mm Operating Temperature 5 to 40 lt 90 relative humidity non condensing Storage Temperature 200 to 60 lt 90 relative humidity non condensing Table 3 Wavelength Locker Specifications Operation and Maintenance Manual 5302WL Wavelength Locker Unit 28 Version 1 0 Sacher Lasertechnik P Appendix Power Supply Specifications AC Voltage Range 90 264 VAC AC Input Frequency 47 63 Hz DC Output Voltage 5VDC at 3 0 Amps 15VDC at 1 6A 15VDC at 0 3Amps DC Output Connector DIN Female 5 Pin 180 Table 4 Power Supply Specifications NOTE In accordance with ongoing efforts to continuously improve our products Triad Technology Inc reserves the right to modify product specifications without notice and without liability for such changes Operation and Maintenance Manual 5302WL Wavelength Locker Unit 29 Version 1 0 y Group Sacher Lasertechni Appendix Factory Service Introduction This section contains information regarding obtaining factory service for the Model 5302Wl The user should not attempt any maintenance or service of this instrument and or accessories Contact Triad Technology for assistance Obtaining Service To obtain information concerning factory service contact Sacher Lasertechnik P Hannah
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