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GaP Biased Detector

Chapter 7: Specifications

Rev A, December 27, 2017

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7.1. Response Curve

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DET25K2

Biased GaP Detector Responsivity

Res

ponsiv

ity (A/W)

Wavelength (nm)

Summary of Contents for DET25K2

Page 1: ...DET25K2 GaP Biased Detector User Guide ...

Page 2: ... of Operation 4 4 4 Dark Current 5 4 5 Junction Capacitance 6 4 6 Bandwidth and Response 6 4 7 Terminating Resistance 7 4 8 Shunt Resistance 7 4 9 Series Resistance 7 4 10 Battery Check 7 4 11 Battery Replacement 8 Chapter 5 Common Operating Circuits 9 Chapter 6 Troubleshooting 11 Chapter 7 Specifications 12 7 1 Response Curve 13 7 2 Mechanical Drawing 14 Chapter 8 Certificate of Conformance 15 Ch...

Page 3: ...bol Description Direct Current Alternating Current Both Direct and Alternating Current Earth Ground Terminal Protective Conductor Terminal Frame or chassis Terminal Equipotentiality On Supply Off Supply In Position of a Bi Stable Push Control Out Position of a Bi Stable Push Control Caution Risk of Electric Shock Caution Hot Surface Caution Risk of Danger Warning Laser Radiation Caution ESD Sensit...

Page 4: ...n internal 12 V bias battery enclosed in rugged aluminum housing The DET25K2 includes a removable 1 optical coupler SM1T1 providing easy mounting of ND filters spectral filters fiber adapters SMA FC and ST style and other 1 stackable lens mount accessories offered by Thorlabs ESD Caution The components inside this instrument are ESD sensitive Take all appropriate precautions to discharge personnel...

Page 5: ...stor values Thorlabs sells a 50 Ω terminator T4119 for best frequency performance and a variable terminator VT2 for output voltage flexibility Note the input impedance of your measurement device since this will act as a terminating resistor A load resistor is not necessary when using current measurement devices 3 Power the DET on using the power switch To check battery voltage see the Battery Chec...

Page 6: ... the level of the output current to expect and the responsivity based upon the incident light Depicted in Figure 1 is a junction photodiode model with basic discrete components to help visualize the main characteristics and gain a better understanding of the operation of Thorlabs photodiodes Figure 1 Photodiode Model 4 2 Responsivity The responsivity of a photodiode can be defined as a ratio of ge...

Page 7: ...oltage builds up This mode of operation exploits the photovoltaic effect which is the basis for solar cells 4 4 Dark Current Dark current is leakage current which flows when a bias voltage is applied to a photodiode Photoconductive mode tends to generate a dark current that varies directly with temperature It can be inferred that dark current can approximately double for every 10 C increase in tem...

Page 8: ...of the RC circuit Drift time tdf Time for electron hole pairs to move from the depletion zone to the electrodes The depletion zone has an intrinsic electric field that accelerates the charges so that they are collected quickly Hence the drift time is generally in the ps time regime Diffusion tdiff Diffusion time for electron hole pairs generated outside of the depletion zone to be collected Depend...

Page 9: ...may range from the order of ten Ω to thousands of MΩ and is dependent on the photodiode material For example an InGaAs detector has a shunt resistance on the order of 10 MΩ while a Ge detector is in the kΩ range This can significantly impact the noise current on the photodiode For most applications however the high resistance produces little effect and can be ignored 4 9 Series Resistance Series r...

Page 10: ...culate the bias voltage more precisely using this feature then a high impedance load is suggested 4 11 Battery Replacement Thorlabs delivers each DET with an A23 12 V battery This battery is readily available at most retail stores as well as through Thorlabs The battery supplied will deliver about 40 hours with a 1 mA load roughly equivalent to a continuous 1 5 mW light source with responsivity 0 ...

Page 11: ...iased to produce a linear response with applied input light The photocurrent generated is based upon the incident light and wavelength and can be viewed on the oscilloscope by attaching a load resistance on the output The function of the RC Filter is to filter any high frequency noise from the input supply which may contribute to a noisy output Figure 3 Amplified Detector Photodetector Transimpeda...

Page 12: ... across the photodiode since point A is held at the same potential as point B by the operational amplifier This eliminates the possibility of dark current Photoconductive mode The photodiode is reversed biased thus improving the bandwidth while lowering the junction capacitance The gain of the detector is dependent on the feedback element RF The bandwidth of the detector can be calculated using th...

Page 13: ...ill have a 1 MΩ input impedance For visible detectors point the detector toward a fluorescent light and verify that a 60 Hz 50 Hz outside the US signal appears on the scope If so the device should be operating properly and the problem may be with the light source or alignment There is an AC signal present when the unit is turned off The detector has an AC path to ground even with the switch in the...

Page 14: ...ery Check Switch Momentary Pushbutton Output BNC DC Coupled Package Size 2 79 x 1 96 x 0 89 70 9 mm x 49 8 mm x 22 5 mm PD Surface Depth6 0 09 2 2 mm Weight 0 10 kg Accessories SM1T1 Coupler SM1RR Retainer Ring Storage Temp 20 to 70 C Operating Temp 10 to 50 C Battery A23 12 VDC 40 mAh Low Battery Voltage7 See Battery Check VOUT Hi Z 9 V VOUT 50 Ω 170 mV 2 Measured with specified bias voltage of 5...

Page 15: ...Chapter 7 Specifications Rev A December 27 2017 Page 13 7 1 Response Curve 100 150 200 250 300 350 400 450 500 550 0 00 0 02 0 04 0 06 0 08 0 10 0 12 DET25K2 Biased GaP Detector Responsivity Responsivity A W Wavelength nm ...

Page 16: ...GaP Biased Detector Chapter 7 Specifications Page 14 TTN134134 D02 7 2 Mechanical Drawing Visit the web for a more detailed mechanical drawing ...

Page 17: ...GaP Biased Detector Chapter 8 Certificate of Conformance Rev A December 27 2017 Page 15 Chapter 8 Certificate of Conformance ...

Page 18: ...rlabs products such as Pure OEM products that means assemblies to be built into a unit by the user e g OEM laser driver cards Components Mechanics and optics Left over parts of units disassembled by the user PCB s housings etc If you wish to return a Thorlabs unit for waste recovery please contact Thorlabs or your nearest dealer for further information Waste Treatment is Your Own Responsibility If...

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