Model 818-ST2 & 918D-ST Series
Contents
1. 90051561 5 5x7 5 4 19_44640 01RevA 5 5x7 5 qxd o 2 1 37 PM Page 1 Model 818 ST2 amp 918D ST Series Slim Profile Wand Detectors User s Manual AD Newport Experience Solutions 90051561 5 5x7 5 4 19_44640 01RevA 5 5x7 5 qxd o 2 1 37 PM Page 2 90051561 5 5x7 5 4 19_44640 01RevA 5 5x7 5 qxd o 2 1 37 PM Pagei Model 818 ST2 amp 918D ST Series Slim Profile Wand Detectors 90051561 5 5x7 5 4 19_44640 01RevA 5 5x7 5 qxd o 2 1 38 PM Page ii Warranty Newport Corporation warrants that this product will be free from defects in material and workmanship and will comply with Newport s published specifications at the time of sale for a period of one year from date of shipment If found to be defective during the warranty period the product will either be repaired or replaced at Newport s option To exercise this warranty write or call your local Newport office or representative or contact Newport headquarters in Irvine California You will be given prompt assistance and return instructions Send the product freight prepaid to the indicated service facility Repairs will be made and the instrument returned freight prepaid Repaired products are warranted for the remainder of the original warranty period or 90 days whichever first occurs Limitation of Warranty The above warranties do not apply to products which have been repaired or modified without Newport s written approval or products subjected to2. Measure the photodetector current or power and record this value A De Place a filter or attenuator of known transmission T in the beam path Record the current again B A filter transmission of 0 001 is a convenient choice 3 The power with the filter in place should be the product of the power measured without the filter and the transmission of the filter ie B AxT If the transmission T of the filter is not known it can be determined by following the steps below 1 Reduce the optical power to a level low enough to avoid saturation but high enough that when it is reduced by the filter it can still be accurately measured 2 Follow steps 1 and 2 in the procedure above 33 Calculate the ratio T B A to determine the transmission of the filter at the wavelength of light used for the measurement The calibrated filter or attenuator can be used with the detector to measure the power of higher power beams Eg Saturation with Pulsed Power Measurements Saturation effects when using pulsed lasers are a complex phenome non and depend upon the wavelength peak power pulse shape aver age power repetition rate and on the type of detection circuit However the test for saturation described immediately above should be used whenever pulsed power measurements are being made Eg Reflections The photodetector surface window material and the attenuator all reflect light The amount of reflected light depends upon the
3. 01RevA 5 5x7 5 qxd o 2 1 38 PM Page 5 Figure 1 918D ST Series detector has an integrated 15 pin D Sub calibration module Figure 2 Calibration modules On the left DB and on the right CM style for 818 ST2 Series detectors Key Features The detectors are in a sturdy economically designed aluminum housing e 818 ST2 Series 818 ST2 IR Series 918D ST SL and 918D ST IR detectors are in a black anodized housing while 818 ST2 UV and 918D ST UV Series UV detectors are in a clear anodized housing to avoid photo contamination The detectors are available with a built in OD3 optical attenuator which is mounted on a thumb slide The actual attenuation of the fil ter varies depending on the wavelength and the batch to batch coating variations The On Off position of the attenuator is automatically detected by the optical meter Models 1918 R 1936 R 2936 R and 1830 R 90051561 5 5x7 5 4 19_44640 01RevA 5 5x7 5 qxd o 2 1 38 PM Page 6 Figure 3 Attenuator ON OFF Switch The detectors can be used hand held or mounted on a post and a post holder Unlike the legacy 818 ST Series detec tors the 818 ST2 and 918D ST Series have the mounting holes on both the sides not at the back of the housing as shown in Figure 4 Figure 4 Location of the mounting holes available on both the sides The detectors have a built in EEPROM which stores the responsivity data measured for every 10 nm step
4. angle of incidence and the polarization of the beam Reflected light does not get absorbed by the detector and therefore is not included in the detector signal The Newport detector and attenuator calibration include the loss due to reflection for incoherent light incident normal to the detector For accurate power measurements the detector should therefore be used at near normal incidence 12 oe 90051561 5 5x7 5 4 19_44640 01RevA 5 5x7 5 qxd o 2 1 38 PM Page 13 2 7 Photodiode Operation When a photon is absorbed in the photodiode an electron hole pair is formed within the device and a voltage is developed across the diode junction If the photodiode terminals are connected a photocurrent proportional to the light intensity will be generated Measuring this photocurrent provides a measurement of the optical power incident upon the detector Newport s power meters utilize an Op Amp to enable unbiased photocurrent measurement Operation with zero bias is called the Photovoltaic Mode R FEEDBACK Op Amp Circuit l Photovoltaic Mode LIGHT Vour Figure 6 Newport 818 ST2 and 918D ST Series detectors in photovoltaic mode 13 90051561 5 5x7 5 4 19_44640 01RevA 5 5x7 5 qxd o 2 1 38 PM Page 14 2 8 Low Power Measurement Considerations Measurements of very low power optical sources are possible with the 818 ST2 and 918D ST series photodetectors Proper detector usage and achievement of accurate results requires t
5. s central active diameter Optical signals being measured should illuminate approximately this same area Care should be taken not to overfill the detector if accuracy is to be maintained 2 4 Detector Saturation For low optical power the photocurrent is linearly proportional to the optical signal incident on the photodiode For high optical powers sat uration of the detector begins to occur and the response signal is no longer linearly proportional to the incident power Optical power mea surements must be made in the linear region to be valid Newport s optical meters measure the current coming from the detector and will let you know before the detector is near its saturation point However even with low total power it is possible to locally saturate the detector by subjecting it to high power densities power per unit area i e a very small beam size This is why it is important to fill the central por tion of the detector s active area as much as possible NOTE The saturation is soft i e the detector output does not sud denly stop increasing but the rate of increase slows For Gaussian and other signals with spatially varying intensities local saturation may occur The onset of saturation is not always obvious and is a common source of inaccurate mea surements 11 90051561 5 5x7 5 4 19_44640 01RevA 5 5x7 5 qxd o 2 1 38 PM Page 12 To determine if the detector is saturating follow the steps below 1
6. shall retain full ownership of Intellectual Property Rights in and to all development process align or assembly technologies developed and other derivative work that may be developed by Newport Customer shall not challenge or cause any third party to challenge the rights of Newport Preservation of Secrecy and Confidentiality and Restrictions to Access Customer shall protect the Newport Programs and Related Materials as trade secrets of Newport and shall devote its best efforts to ensure that all its personnel protect the Newport Programs as trade secrets of Newport Corporation Customer shall not at any time disclose Newport s trade secrets to any other person firm organization or employee that does not need consistent with Customer s right of use hereunder to obtain access to the Newport Programs and Related Materials These restrictions shall not apply to information 1 generally known to the public or obtainable from public sources 2 readily apparent from the keyboard operations visual display or output reports of the Programs 3 previously in the possession of Customer or subse quently developed or acquired without reliance on the Newport Programs or 4 approved by Newport for release without restriction Trademarks The Newport logo is a registered trademark of Newport Corporation in Austria Barbados Benelux Canada the People s Republic of China Denmark France Germany Great Britain Ireland Japan the Republic of K
7. within the specified spectral range for the detector The respon sivity data is stored for both with and without the attenua tor filter in the beam path The detectors are hot plug gable enabling this data to be uploaded onto the power meter when the detector is first connected to the instru ment allowing for corrections of the responsivity as a function of the wavelength selected by the user 90051561 5 5x7 5 4 19_44640 01RevA 5 5x7 5 qxd o 2 1 38 PM Page 7 918D ST Series detectors include a thermistor which measures the temperature of the detector and allows the optical meter to make numerical corrections of the responsivity as a function of temperature 1 4 Specifications Model w DB15 918D ST UV 918D ST SL 918D ST IR Connector 818 ST2 UV DB 818 ST2 DB 818 ST2 IR DB Spectral Range nm 200 to 1100 400 to 1100 780 to 1800 Power Density Average Max 0 20 2 00 2 00 w Attenuator W cm Power Density Average 0 50 5 00 3 00 Maximum w o Attenuator mW cm Pulse Energy Maximum 0 10 1 00 0 35 w Attenuator yJ cm Pulse Energy Maximum 0 10 1 00 0 35 w o Attenuator nJ cm Uniformity 2 2 3 Linearity 0 5 Calibration Uncertainty w o Attenuator 4 200 219 nm 2 220 349 nm 1 350 949 nm 4 950 1100 nm 1 400 940 nm 4 941 1100 nm 2 780 910 nm 2 911 1700 nm 4 1701 1800 nm Calibration Uncertainty 8 200 219 nm 1 40
8. 0 940 nm 5 780 910 nm w Attenuator 2 220 349 nm 4 941 1100 nm 2 911 1700 nm 1 350 949 nm 4 1701 1800 nm 4 950 1100 nm Rise Time us lt 3 5 Shunt Resistance MQ typ 2200 20 005 Reverse Bias Max V 2 00 NEP pW VHz 0 02 0 02 4 00 Material UV Enhanced Silicon Silicon Germanium Shape Wand Attenuator OD3 Built In When measured with beam centered and filling 80 of active area Table 2 Specifications Table 90051561 5 5x7 5 4 19_44640 01RevA 5 5x7 5 qxd o 2 1 38 PM Page 8 Making Measurements Attach the 15 pin D Sub connector of an 818 ST2 or a 918D ST Series detector to Newport s optical power meters Refer to the power meter user manual for details on how to operate the meter In order to assure good electrical connectivity it is recommended that the thumbscrews located on both sides of the connector be hand tight ened Each detector comes with its unique calibrated responsivity data encoded in an EEPROM built into the connector When the detector is connected to a power meter for the first time manually set up the wavelength from the power meter Calibration data is provided for the detector with and without the optical attenuator Newport s 1830 R 1918 R 1928 C and 1936 2936 R optical meters read the EEP ROM data not only during initial power up but any time a detector is connected and subsequently sensed by the optical meter To ensure an accurat
9. e measurement it is recommended that the detector be mounted securely on an optical table Keep in mind that slight move ment of the detector can easily misalign an optical beam from the detector active area Any optical surface will change its reflectivity depending on the beam incident angle All Newport optical detectors are calibrated with the detector housing surface normal to the incident beam with the reflec tivity from the detector air interface and from the attenuator already taken into account during calibration 818 ST2 and 918D ST Series detectors have a built in optical attenua tor which can be manually switched into or out of the optical path using a slider Attenuator ON and OFF markings indicate the atten uator position see Figure 5 A built in sensor automatically detects the attenuator position signaling the power meter to use the appropri ate responsivity for the detector attenuator combination Figure 5 Attenuator in the ON Position 8 oe 90051561 5 5x7 5 4 19_44640 01RevA 5 5x7 5 qxd o 2 1 38 PM Page 9 1 5 Cleaning The detector must not be disassembled for cleaning purposes The attenuator filter can be cleaned by sliding the filter to the ON posi tion Use the proper optics grade lint free cotton swabs and organic solvent such as optical grade isopropyl alcohol reagent grade ace tone or lens cleaning solution NOTE Kleenex and Kim wipes contain wood and fib
10. ector is used with a Newport optical meter it is operated essentially without bias voltage as depicted in Figure 6 The effective time constant of the detector amplifier combination may be much slower than the characteristic time of the signal Nonetheless if the detector amplifier combination does not become saturated effective integration of the signal will occur and accurate power measurements of very short pulses can be made Additionally if the repetition rate or duty cycle is sufficiently high good average power measurements can be made Usually it is helpful to turn on the analog filter 5Hz low pass to smooth the DC component so that the optical meter will make consistent measurements of the average power 15 90051561 5 5x7 5 4 19_44640 01RevA 5 5x7 5 qxd o 2 1 38 PM Page 16 3 Factory Service al Introduction This section contains information regarding obtaining factory service for the 818 ST2 and 918D ST Series Wand Detectors The user should not attempt any maintenance or service of this product Contact Newport Corporation or your Newport representative for assistance The detector calibration uncertainty is warranted for a period of 1 year with a normal use 3 2 Obtaining Service To obtain information concerning factory service contact Newport Corporation or your Newport representative Please have the follow ing information available 1 Product model number 2 Product serial number 3 Description of the p
11. eees 3 1 2 Product Model 8 ciisciieiaiadiintaviieadedtiieneienen ded 4 13 818 ST2 and 918D ST Series Features oo eee 4 14 SPCCHICAUONS ve sesiaeliavieaad a E EE EEE ERa 7 Makin MeasurementSsssneagn aaa R E NENS 8 1 5 CUS aman sea a a a E E 9 1 6 Temperature and Humidity sisisi sisisesiiesasnsrsiseiseiosissa 9 Section 2 Calibration Uncertainties and Limitations 2 1 Spectral RESpOmse ccceivces scariest aenansareeendes 10 2 2 Calibration Uncertainties and Service ceccseeeeceesereeeees 10 2 3 By avon ci sil aaea coperereer ercperrecter ei iser treet ANE ere 11 24 DetectOn SaturatlOn e c c0ssssscsceecsasesoseveevoseeedersesvaxineescusavies 11 2 5 Saturation with Pulsed Power Measurements 12 2 6 IGG CHOMS cenna fase soucaracet tags canes a R 12 2T Photodiode Operation sscan niis 13 2 8 Low Power Measurement Considerations cccccceees 14 2 8 1 Noise Characteristics cccccccccsesssececessssceececesseaeeeecsessaeeeees 14 2 8 2 Ambient Light and Electrical Offsets 0 0 0 eeeeeeeeeneeee 15 2 9 Using the Detector for Non CW Measurements 15 Section 3 Factory Service 3 1 Tit OG CHOM cdsisccsdsacs euedvacscaestod tes caneedssgdeasbvesbavasdsaesctaee toes 16 3 2 Obtaining Service wire dee enn a a 16 3 3 Services Foof Mancini es T EE 17 1 90051561 5 5x7 5 4 19_44640 01RevA 5 5x7 5 qxd o 2 1 38 PM Page 2 List of Figures Figure 1 918D ST Series detector has a
12. er glass respectively and will scratch optical surfaces Care must be taken not to touch the photodiode window or attenuator with bare fingers Contaminants may cause inaccurate measurements particularly at ultraviolet wavelengths where absorption is common Potentially large measurement errors can be induced by scratches digs and damage to the optical surfaces of the attenuator or detector For dust removal use pressurized gas filtered dry nitrogen and lint free cotton swabs dabbed in an organic solvent 11 6 Temperature and Humidity The temperature range of 5 to 50 C should not be exceeded and the detector should not be exposed to humidity levels greater than 70 The photodiode sensitivity increases with temperature mainly for wavelengths longer than the peak response wavelength The tempera ture of the 918D ST series detectors is monitored with a thermistor and the responsivity is numerically compensated to keep the calibra tion accurate within specification throughout the operating tempera ture for a given wavelength 90051561 5 5x7 5 4 19_44640 01RevA 5 5x7 5 qxd o 2 1 38 PM Page 10 2 Calibration Uncertainties and Limitations 2 1 Spectral Response The response of the detector depends on the wavelength of the inci dent light The photodiode is transparent for photon energies less than the band gap which determines the long wavelength infrared sensitivity limit The short wavelength limit is determined by the p
13. eturn Material Authorization Number RMA Return the product to Newport Corporation freight prepaid clearly marked with the RMA and we will either repair or replace it at our discretion Newport is not responsible for damage occurring in transit and is not obligated to accept products returned without an RMA E mail rma service newport com When calling Newport Corporation please provide the customer care representativewith the following information e Your Contact Information e Serial number or original order number e Description of problem i e hardware or software To help our Technical Support Representatives diagnose your problem please note the following conditions e Is the system used for manufacturing or research and development e What was the state of the system right before the problem e Have you seen this problem before If so how often e Can the system continue to operate with this problem Or is the system non operational e Can you identify anything that was different before this problem occurred iv oe 90051561 5 5x7 5 4 19_44640 01RevA 5 5x7 5 qxd o 2 1 38 PM Page 1 Table of Contents Warranty eaa EE EEA E AE E ii Technical Support Contacts sisson n EE a iv Table of CONtEntS ceiien ipenn an raia E aai aa aA araia 1 List Of PIS UNSS oo o ae AEE E EE AE TERNE ORNE 2 List of Tables sirontaa ai n 2 Section 1 General Information 1 1 Unpacking and Inspection 00 eee eeeeeeeeeeeeereeeeeeneen
14. he understanding of a number of effects that limit the device performance which are dis cussed below 2 8 1 Noise Characteristics The lower limits of optical detection are determined by the noise char acteristics of the detector and or amplifier Theory predicts that the photodiode noise is largely thermal Johnson noise associated with the effective resistance of the photodiode and shot noise from dark current Additionally there is Johnson noise contributed by the resis tance of the amplifier s feedback resistor The dark current at a 10mV bias voltage is measured and used to define the effective resistance of the photodiode known as the shunt resistance R Voias Taare Where Vpias 1OmV shunt 7 bias bias Ideally an input amplifier connected as in Figure 6 would have no off set voltage and there would be no dark current In practice though a small bias usually exists For non CW measurements the light detec tion limit is more generally expressed as the intensity of light required to produce a current equal to the noise current i e a signal to noise level of 1 This is called the noise equivalent power NEP and is expressed as NEP Noise Current Sensitivity W VHz with sensitivity defined as the current generated by the photodiode for a given incident power at a specific wavelength NEP varies inversely with the spectral response of the photodiode and depends on the wavelength the noise frequency f and band
15. hotodiode manufacturing process and possibly in the case of silicon photodiodes by strong window absorption The photodiode response is commonly measured in amps of photocurrent per watt of incident optical power The response curves for the photodetector are shown on the calibration report shipped with each detector G 2 2 Calibration Uncertainties and Service STATEMENT OF CALIBRATION The uncertainty and calibration of this photodetectors are traceable to National Institute of Standards and Technology NIST or an equivalent body through equipment which is cal ibrated at planned intervals and by comparison to certified standards maintained at Newport Corporation Newport Corporation calibrates its detectors using secondary stand ards directly traceable to NIST and or NRC The absolute uncertainty of the photodetector calibration is indicated on the calibration report Detector response can change with time at different wavelengths especially in the ultraviolet and should be returned for recalibration at 12 month intervals to ensure confidence in the accuracy of the mea surement For recalibration services contact Newport Corporation at 800 222 6440 10 oe 90051561 5 5x7 5 4 19_44640 01RevA 5 5x7 5 qxd o 2 1 38 PM Page 11 2 3 Uniformity Fabrication processes may cause the response of the detector to vary slightly over the detector surface Calibration involves illumination of approximately 70 of the detector
16. leaning of the attenuator filter See Section 1 5 for a description on how to clean this part 90051561 5 5x7 5 4 19_44640 01RevA 5 5x7 5 qxd o 2 1 38 PM Page 4 11 2 Product Models Model Detector Type Connector Type 818 ST2 Silicon BNC 818 ST2 DB Silicon 15 pin D Sub 818 ST2 CM Silicon 8 pin Din 818 ST2 UV UV Enhanced Silicon BNC 818 ST2 UV DB UV Enhanced Silicon 15 pin D Sub 818 ST2 UV CM UV Enhanced Silicon 8 pin Din 818 ST2 IR Germanium BNC 818 ST2 IR DB Germanium 15 pin D Sub 818 ST2 IR CM Germanium 8 pin Din 918D ST SL Silicon 15 pin D Sub 918D ST UV UV Enhanced Silicon 15 pin D Sub 918D ST IR Germanium 15 pin D Sub G Table 1 Available 818 ST2 and 918D ST Series Models 1 3 818 ST2 and 918D ST Series Features 818 ST2 and 918D ST Series detectors utilize Silicon UV enhanced Silicon and Germanium photodiodes covering a broad wavelength range from 200 to 1800 nm These highly sensitive low noise photo diodes enable measurements from sub pW to 3 mW optical power The built in attenuator extends the dynamic range into the watt range 818 ST2 Series detectors are terminated with a BNC connector A 15 pin D Sub type connector containing the calibration data is use to plug in to Newport s optical power meters 918D ST Series detectors are directly terminated with a 15 pin D Sub type connector Please check www newport com for the latest product offering 90051561 5 5x7 5 4 19_44640
17. n integrated 15 pin D Sub Calibration Mod le sssrinin niinn 5 Figure 2 Calibration modules On the left DB and on the right CM style for 818 ST2 Series detectors eee 5 Figure 3 Attenuator ON OFF Switch oo eeeeeeeeeereeeeeereeenee 6 Figure 4 Location of the mounting holes available on both the sides 6 Figure 5 Attenuator in the ON Position oc eee eeeeeeeeereteeeeees 8 Figure 6 Newport 818 ST2 and 918D ST Series detectors in PHOtOVoltaie Mode sisanne 13 List of Tables Table 1 Available 818 ST2 and 918D ST Series Models 4 Table 2 Specifications Table sssini 7 90051561 5 5x7 5 4 19_44640 01RevA 5 5x7 5 qxd o 2 1 38 PM Page 3 General Information This guide contains information necessary for using model 818 ST2 and 918D ST series slim profile wand photodetectors Please read through the guide before attempting to make optical power measure ments or energy measurements 1 1 Unpacking and Inspection The 818 ST2 and 918D ST Series photodetectors are shipped in a foam padded cardboard box along with this user s manual and the calibration report The calibration report is unique to each detector and should be archived for future reference The calibration interval recom mended for these detectors is 12 months Please make sure that these items are received in good condition NOTE Fragile parts are contained Use caution when handling The only user serviceable part of this detector is the c
18. orea Spain Sweden and the United States Newport is a registered trademark of Newport Corporation in Austria Barbados Benelux the People s Republic of China Denmark France Germany Ireland Japan the Republic of Korea Spain and Sweden Service Information This section contains information regarding factory service for the source The user should not attempt any maintenance or service of the system or optional equipment beyond the procedures outlined in this manual Any problem that cannot be resolved should be referred to Newport Corporation iii 90051561 5 5x7 5 4 19_44640 01RevA 5 5x7 5 qxd o 2 1 38 PM Page iv Technical Support Contacts North America Europe Newport Corporation Service Dept Newport MICRO CONTROLE S A 1791 Deere Ave Irvine CA 92606 Zone Industrielle Telephone 949 253 1694 45340 Beaune la Rolande FRANCE Telephone 800 222 6440 x31694 Telephone 33 02 38 40 51 56 Asia Newport Opto Electronics Technologies Wuxi Co Ltd RIMMER 7 ARAR TARA HMEGOMLE J3 87 F 204028 Lot J3 8 Wuxi Export Processing Zone New District Jiangsu China 204028 Telephone 86 510 8113 2999 Fax 86 510 8526 9050 Newport Corporation Calling Procedure If there are any defects in material or workmanship or a failure to meet specifications promptly notify Newport s Returns Department by calling 1 800 222 6440 or by visiting our website at www newport com returns within the war ranty period to obtain a R
19. roblem If the instrument is to be returned to Newport Corporation you will be given a Return Authorization Number which you should reference in your shipping documents Please fill out a copy of the service form located on the following page and have the information ready when contacting Newport Corporation Return the completed service form with the instrument 16 90051561 5 5x7 5 4 19_44640 01RevA 5 5x7 5 qxd o 2 1 38 PM Page 17 Bel Service Form GLO Newport Corporation USA Office 800 222 6440 Newport FAX 949 253 1479 Experience Solutions Name Return Authorization Please obtain RA prior to return of item Company Address Date Country Phone Number P O Number Fax Number Item s Being Returned Model Serial Description Reason for return of goods please list any specific problems 90051561 5 5x7 5 4 19_44640 01RevA 5 5x7 5 qxd o 2 1 38 PM Page 18 Newport Corporation Worldwide Headquarters 1791 Deere Avenue Irvine CA 92606 In U S 800 222 6440 Tel 949 863 3144 Fax 949 253 1680 Internet sales newport com GY Newport Experience Solutions Visit Newport Online at www newport com Newport Corporation Irvine California has been certified compliant with ISO 9001 by the British Standards Institution oe
20. unusual physical thermal or electrical stress improper installation misuse abuse accident or negli gence in use storage transportation or handling This warranty also does not apply to fuses batteries or damage from battery leakage THIS WARRANTY IS IN LIEU OF ALL OTHER WARRANTIES EXPRESSED OR IMPLIED INCLUDING ANY IMPLIED WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR USE NEWPORT CORPORATION SHALL NOT BE LIABLE FOR ANY INDIRECT SPECIAL OR CONSEQUENTIAL DAMAGES RESULTING FROM THE PURCHASE OR USE OF ITS PRODUCTS First printing 2012 2012 by Newport Corporation Irvine CA All rights reserved No part of this manual may be reproduced or copied without the prior written approval of Newport Corporation This manual has been provided for information only and product specifications are subject to change without notice Any change will be reflected in future printings Newport Corporation 1791 Deere Avenue Irvine CA 92606 USA Part No 90051561 Rev A ii 90051561 5 5x7 5 4 19_44640 01RevA 5 5x7 5 qxd o 2 1 38 PM Page iii Confidentiality amp Proprietary Rights Reservation of Title The Newport programs and all materials furnished or produced in connection with them Related Materials contain trade secrets of Newport and are for use only in the manner expressly permitted Newport claims and reserves all rights and benefits afforded under law in the Programs provided by Newport Corporation Newport
21. width Af Noise and dark current generally increase exponentially with detector temperature so it is best to keep the temperature close to 25 C 14 90051561 5 5x7 5 4 19_44640 01RevA 5 5x7 5 qxd o 2 1 38 PM Page 15 2 8 2 Ambient Light and Electrical Offsets Good measurement technique dictates that the effects of ambient light should be reduced as much as possible when using photodiodes Although the photocurrent generated by ambient light can be easily zeroed out the shot noise associated with the photocurrent will not be zeroed nor will any changes in the ambient light levels which might be caused by people moving around in the room A small electronic offset will always be present with semiconductor detectors caused by an interaction of the detector shunt resistance with voltage offsets in the amplifier circuitry The offset can be removed by use of the optical meter s zero function Please note however that the offset is a func tion of the temperature of both the photodiode and the amplifier inside the optical meter When measuring very low light levels it is best to re zero the meter whenever you think that the temperature of the detector or the optical meter may have changed For instance it is good practice to re zero the meter after a warm up period of about 30 minutes Refer to your optical meter manual for details regarding the zeroing procedure aJ Using the Detector for Non CW Measurements When the photodet
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