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HgCdTe (MCT) Amplified Photodetectors


  • HgCdTe (MCT) Detectors with Optically Immersed Sensors
  • Three Models Available Covering 2.0 to 10.6 µm
  • Adjustable Gain Selection

PDAVJ8

2.0 - 8.0 µm,
DC to 100 MHz

PDAVJ10

2.0 - 10.6 µm,
DC to 100 MHz

PDAVJ5

2.7 - 5.0 µm,
DC to 1 MHz

Related Items


Please Wait
MIR Photodetector Selection Guidea
Item # (Detector) Wavelength
Range
Maximum
Bandwidth
Thermoelectric
Cooler
PDA10DT (InGaAs) 0.9 - 2.57 µm 1,000 kHz Yes
PDA10D2 (InGaAs) 0.9 - 2.6 µm 25,000 kHz No
PDA10PT (InAsSb) 1.0 - 5.8 µm 1,600 kHz Yes
PDA07P2 (InAsSb) 2.7 - 5.3 µm 9 MHz No
PDA30G (PbS) 1.0 - 2.9 µm 1 kHz No
PDA20H (PbSe) 1.5 - 4.8 µm 10 kHz No
PDA10JT (HgCdTe) 2.0 - 5.4 µm 160 kHz Yes
PDAVJ8 (HgCdTe) 2.0 - 8.0 µm 100 MHz No
PDAVJ10 (HgCdTe) 2.0 - 10.6 µm 100 MHz No
PDAVJ5 (HgCdTe) 2.7 - 5.0 µm 1 MHz No
  • See the Cross Reference tab for our full selection of photodetectors.

Click for Details

A hyperhemispherical lens forms an image on a virtual plane behind the sensor element, resulting in an effective optical area greater than the physical sensor area.

Click for Details

A standard hemispherical immersion lens forms an image in the plane of the sensor element.

Features

  • Photovoltaic Detectors Sensitive to MIR Light:
    • PDAVJ8: 2.0 - 8.0 µm
    • PDAVJ10: 2.0 - 10.6 µm
    • PDAVJ5: 2.7 - 5.0 µm
  • High Bandwidth:
    • PDAVJ8: True DC - 100 MHz
    • PDAVJ10: True DC - 100 MHz
    • PDAVJ5: True DC - 1 MHz
  • Effective Detector Area: 1 mm2 (1 mm x 1 mm)
  • Post Mountable in Two Orientations Using Universal 8-32 & M4 Tapped Holes
  • External SM1 (1.035"-40) Threads and Internal SM05 (0.535"-40) Threads
  • Location-Specific Power Adapter Included

Thorlabs' Amplified HgCdTe (mercury cadmium telluride, MCT) Photovoltaic Detectors are sensitive to MIR light. A rotary switch controls the gain amplifier (shown in the photo below), allowing performance to be optimized for a variety of applications. The gain switch features eight discrete steps from 0 to 30 dB (Item #s PDAVJ8 and PDAVJ10) or 0 to 42 dB (Item # PDAVJ5). For best results, we recommend connecting the output cable (not included) to a 50 Ω termination.

Each HgCdTe (MCT) sensor element is integrated with a hyperhemispherical GaAs lens to achieve optical immersion, and each detector is provided with a wedged ZnSe window that is AR-coated for the 2 - 13 µm wavelength range.

MCT Detector Side View
Click to Enlarge

Side View Showing Gain Adjuster

The detector package incorporates many of the same mechanical features as our other mounted photodetectors. External SM1 (1.035"-40) and internal SM05 (0.535"-40) threading allows Ø1" lens tubes or Ø1/2" lens tubes to be mounted in front of the detector element. Universal 8-32 & M4 tapped holes connect a Ø1/2" post to the housing in one of two perpendicular orientations. A location-specific power supply is included with each detector.

Optically Immersed Sensor Element
Optical Immersion is used in these MCT detectors to produce a 1 mm2 effective detector area, approximately two orders of magnitude larger than the actual sensor, resulting in increased responsivity and reduced capacitance. This technique is performed by integrating the sensor element with a GaAs hyperhemispherical microlens, which has a high refractive index (n = 3.3) and is transparent to MIR wavelengths. The diagrams to the right illustrate the benefit of using a hyperhemispherical lens, rather than a hemispherical lens. A hemispherical lens focuses light onto the sensor plane (left diagram) and produces an image with dimensions larger than the physical sensor by a factor of n. The hyperhemispherical lens (right diagram) forms an image on a virtual focal plane located behind the sensor, and this image has dimensions larger than the physical sensor by a factor of n2. Note that the acceptance angle is reduced to 35° by the hyperhemispherical lens, in contrast to the 180° acceptance angle that would be obtained if a hemispherical lens were used.

All specifications are valid at 23 ± 5°C and 45 ± 15% relative humidity.

Item # PDAVJ8 PDAVJ10 PDAVJ5
Optical Specifications
Wavelength Range 2.0 - 8.0 μm 2.0 - 10.6 μm 2.7 - 5.0 μm
Peak Wavelength (λP) 6.5 μm 6.5 μm 4.75 μm
Window Material ZnSe
Saturation Input Power 250 µW 500 µW 200 µW
Max Input Power
(Photodiode Damage Threshold)
CW or >1 µs Pulse: 2.5 W/cm2
<1 µs Pulse: 10 kW/cm
2
Electrical Specifications
Responsivity × Effective Detector Width @ λP ≥0.04 A·mm/Wa ≥0.01 A·mm/Wa -
Current Responsivity @ λP - - ≥1 A/W
Detectivity (D*) @ λP ≥6.0×108 cm·Hz1/2·W-1 ≥2.0×108 cm·Hz1/2·W-1 ≥1.5×1010 cm·Hz1/2·W-1
Gain Adjustment Range 30 dB 30 dB 42 dB
Gain Steps 8
Conversion Gain @ Gain = 8, λP 6000 V/W 4000 V/W 200 000 V/W
Conversion Gain @ Gain = 1, λP 185 V/W 120 V/W 1500 V/W
Output Bandwidth (3 dB) DC - 100 MHzb DC - 100 MHzb DC - 1 MHzc
Noise Equivalent Power (NEP)d 170 pW/Hz1/2 210 pW/Hz1/2 14 pW/Hz1/2
Output Voltage (Max) 0 - 1.0 V (50 Ω)
0 - 2.0 V (Hi-Z)
Output Impedance BNC, 50 Ω
Output Current (Max) 50 mA
Output Offset Voltage <±25 mV
General Specifications
Optical Input Free Space
Electrical Output BNC
Detector Element HgCdTe (MCT), Optically Immersed
Effective Detector Size 1 mm x 1 mm, Single Layer 1 mm x 1 mm, Multilayer 1 mm x 1 mm, Multilayer
Housing Dimensions 70.9 mm × 54.1 mm × 22.5 mm
(2.79" × 2.13" × 0.89")
Depth of Detector Surfacee 4.3 mm
Depth of Protective Windowe 1.1 mm
Weight Detector: 0.18 lbs (80 g)
Power Supply: 1.6 lbs (530 g)
Included Power Supply 100 - 120 VAC or 220 - 240 VAC (50 - 60 Hz)
Operating Temperature 15 to 30 °C
Storage Temperature 0 to 45 °C
  • Due to the multilayer construction of the sensor chips used in these detectors, the responsivity is inseparable from the sensor width.
  • Independent of Gain Step
  • Specified at Gain Step 1; Bandwidth Varies with Each Gain Step
  • Minimum; Specified from DC to Cut-Off Frequency
  • Measured from Front of Detector Housing, Not Including the Threaded Section

Output Signal

BNC Female

BNC Female

0 - 1.0 V at 50 Ω
0 - 2.0 V at High Z
50 mA Max Current

Power Input

3-Pin Female

BNC Female

Photodiode Tutorial

Theory of Operation

A junction photodiode is an intrinsic device that behaves similarly to an ordinary signal diode, but it generates a photocurrent when light is absorbed in the depleted region of the junction semiconductor. A photodiode is a fast, highly linear device that exhibits high quantum efficiency based upon the application and may be used in a variety of different applications.

It is necessary to be able to correctly determine 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.

Equation 1
Photodiode Circuit Diagram
Figure 1: Photodiode Model

Photodiode Terminology

Responsivity
The responsivity of a photodiode can be defined as a ratio of generated photocurrent (IPD) to the incident light power (P) at a given wavelength:

Equation 2

Modes of Operation (Photoconductive vs. Photovoltaic)
A photodiode can be operated in one of two modes: photoconductive (reverse bias) or photovoltaic (zero-bias). Mode selection depends upon the application's speed requirements and the amount of tolerable dark current (leakage current).

Photoconductive
In photoconductive mode, an external reverse bias is applied, which is the basis for our DET series detectors. The current measured through the circuit indicates illumination of the device; the measured output current is linearly proportional to the input optical power. Applying a reverse bias increases the width of the depletion junction producing an increased responsivity with a decrease in junction capacitance and produces a very linear response. Operating under these conditions does tend to produce a larger dark current, but this can be limited based upon the photodiode material. (Note: Our DET detectors are reverse biased and cannot be operated under a forward bias.)

Photovoltaic
In photovoltaic mode the photodiode is zero biased. The flow of current out of the device is restricted and a voltage builds up. This mode of operation exploits the photovoltaic effect, which is the basis for solar cells. The amount of dark current is kept at a minimum when operating in photovoltaic mode.

Dark Current
Dark current is leakage current that flows when a bias voltage is applied to a photodiode. When operating in a photoconductive mode, there tends to be a higher dark current that varies directly with temperature. Dark current approximately doubles for every 10 °C increase in temperature, and shunt resistance tends to double for every 6 °C rise. Of course, applying a higher bias will decrease the junction capacitance but will increase the amount of dark current present.

The dark current present is also affected by the photodiode material and the size of the active area. Silicon devices generally produce low dark current compared to germanium devices which have high dark currents. The table below lists several photodiode materials and their relative dark currents, speeds, sensitivity, and costs.

MaterialDark CurrentSpeedSpectral RangeCost
Silicon (Si) Low High Speed Visible to NIR Low
Germanium (Ge) High Low Speed NIR Low
Gallium Phosphide (GaP) Low High Speed UV to Visible Moderate
Indium Gallium Arsenide (InGaAs) Low High Speed NIR Moderate
Indium Arsenide Antimonide (InAsSb) High Low Speed NIR to MIR High
Extended Range Indium Gallium Arsenide (InGaAs) High High Speed NIR High
Mercury Cadmium Telluride (MCT, HgCdTe) High Low Speed NIR to MIR High

Junction Capacitance
Junction capacitance (Cj) is an important property of a photodiode as this can have a profound impact on the photodiode's bandwidth and response. It should be noted that larger diode areas encompass a greater junction volume with increased charge capacity. In a reverse bias application, the depletion width of the junction is increased, thus effectively reducing the junction capacitance and increasing the response speed.

Bandwidth and Response
A load resistor will react with the photodetector junction capacitance to limit the bandwidth. For best frequency response, a 50 Ω terminator should be used in conjunction with a 50 Ω coaxial cable. The bandwidth (fBW) and the rise time response (tr) can be approximated using the junction capacitance (Cj) and the load resistance (RLOAD):

Equation 3

Noise Equivalent Power
The noise equivalent power (NEP) is the generated RMS signal voltage generated when the signal to noise ratio is equal to one. This is useful, as the NEP determines the ability of the detector to detect low level light. In general, the NEP increases with the active area of the detector and is given by the following equation:

Photoconductor NEP

Here, S/N is the Signal to Noise Ratio, Δf is the Noise Bandwidth, and Incident Energy has units of W/cm2. For more information on NEP, please see Thorlabs' Noise Equivalent Power White Paper.

Terminating Resistance
A load resistance is used to convert the generated photocurrent into a voltage (VOUT) for viewing on an oscilloscope:

Equation 4

Depending on the type of the photodiode, load resistance can affect the response speed. For maximum bandwidth, we recommend using a 50 Ω coaxial cable with a 50 Ω terminating resistor at the opposite end of the cable. This will minimize ringing by matching the cable with its characteristic impedance. If bandwidth is not important, you may increase the amount of voltage for a given light level by increasing RLOAD. In an unmatched termination, the length of the coaxial cable can have a profound impact on the response, so it is recommended to keep the cable as short as possible.

Shunt Resistance
Shunt resistance represents the resistance of the zero-biased photodiode junction. An ideal photodiode will have an infinite shunt resistance, but actual values may range from the order of ten Ω to thousands of MΩ and is dependent on the photodiode material. For example, and 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.

Series Resistance
Series resistance is the resistance of the semiconductor material, and this low resistance can generally be ignored. The series resistance arises from the contacts and the wire bonds of the photodiode and is used to mainly determine the linearity of the photodiode under zero bias conditions.

Common Operating Circuits

Reverse Biased DET Circuit
Figure 2: Reverse-Biased Circuit (DET Series Detectors)

The DET series detectors are modeled with the circuit depicted above. The detector is reverse biased to produce a linear response to the applied input light. The amount of photocurrent generated is based upon the incident light and wavelength and can be viewed on an 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 that may contribute to a noisy output.

Reverse Biased DET Circuit
Figure 3: Amplified Detector Circuit

One can also use a photodetector with an amplifier for the purpose of achieving high gain. The user can choose whether to operate in Photovoltaic of Photoconductive modes. There are a few benefits of choosing this active circuit:

  • Photovoltaic mode: The circuit is held at zero volts 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 the following:

Equation 5

where GBP is the amplifier gain bandwidth product and CD is the sum of the junction capacitance and amplifier capacitance.

Effects of Chopping Frequency

The photoconductor signal will remain constant up to the time constant response limit. Many detectors, including PbS, PbSe, HgCdTe (MCT), and InAsSb, have a typical 1/f noise spectrum (i.e., the noise decreases as chopping frequency increases), which has a profound impact on the time constant at lower frequencies.

The detector will exhibit lower responsivity at lower chopping frequencies. Frequency response and detectivity are maximized for

Photoconductor Chopper Equation


Posted Comments:
daniel.cremons  (posted 2018-09-06 17:50:29.52)
I have the PDAVJ8 and when using the power supply in the 115 V mode (to match my supply; I'm in the US), I see a 30 MHz sawtooth in the signal which is about 20 mV at 0 gain. When I switch the power supply to the 230 V setting the sawtooth goes away and the detector seems to be operating as normal. Could my power supply have gotten the settings switched or is there some other cause of the sawtooth?
nreusch  (posted 2018-09-27 09:38:22.0)
This is a response from Nicola at Thorlabs. Thank you for your inquiry. We could not reproduce the 30 MHz saw tooth, so there might be an issue with the PSU. As you have not selected “Contact Me” in the feedback form, please get in contact with your local Thorlabs Tech Support team for troubleshooting.

The following table lists Thorlabs' selection of photodiodes and photoconductive detectors. Item numbers in the same row contain the same detector element.

Photodetector Cross Reference
Wavelength Material Unmounted
Photodiode
Unmounted
Photoconductor
Mounted
Photodiode
Biased
Detector
Amplified
Detector
150 - 550 nm GaP FGAP71 - SM05PD7A DET25K2 PDA25K2
200 - 1100 nm Si FDS010 - SM05PD2A
SM05PD2B
DET10A2 PDA10A2
Si - - SM1PD2A - -
320 - 1000 nm Si - - - - PDA8A(/M)
320 - 1100 nm Si FD11A - SM05PD3A - PDF10A(/M)
Si - - - DET100A2 PDA100A2
340 - 1100 nm Si FDS10X10 - - - -
350 - 1100 nm Si FDS100
FDS100-CAL a
- SM05PD1A
SM05PD1B
DET36A2 PDA36A2
Si FDS1010
FDS1010-CAL a
- SM1PD1A
SM1PD1B
- -
400 - 1000 nm Si - - - - PDA015A(/M)
FPD310-FS-VIS
FPD310-FC-VIS
FPD510-FC-VIS
FPD510-FS-VIS
FPD610-FC-VIS
FPD610-FS-VIS
400 - 1100 nm Si FDS015 b - - - -
Si FDS025 b
FDS02 c
- - DET02AFC(/M)
DET025AFC(/M)
DET025A(/M)
DET025AL(/M)
-
400 - 1700 nm Si & InGaAs DSD2 - - - -
500 - 1700 nm InGaAs - - - DET10N2 -
750 - 1650 nm InGaAs - - - - PDA8GS
800 - 1700 nm InGaAs FGA015 - - - PDA015C(/M)
InGaAs FGA21
FGA21-CAL a
- SM05PD5A DET20C2 PDA20C(/M)
PDA20CS2
InGaAs FGA01 b
FGA01FC c
- - DET01CFC(/M) -
InGaAs FDGA05 b - - - PDA05CF2
InGaAs - - - DET08CFC(/M)
DET08C(/M)
DET08CL(/M)
PDF10C(/M)
800 - 1800 nm Ge FDG03
FDG03-CAL a
- SM05PD6A DET30B2 PDA30B2
Ge FDG50 - - DET50B2 PDA50B2
Ge FDG05 - - - -
900 - 1700 nm InGaAs FGA10 - SM05PD4A DET10C2 PDA10CS2
900 - 2600 nm InGaAs FD05D - - DET05D2 -
FD10D - - DET10D2 PDA10D2
950 - 1650 nm InGaAs - - - - FPD310-FC-NIR
FPD310-FS-NIR
FPD510-FC-NIR
FPD510-FS-NIR
FPD610-FC-NIR
FPD610-FS-NIR
1.0 - 2.9 µm PbS - FDPS3X3 - - PDA30G(-EC)
1.0 - 5.8 µm InAsSb - - - - PDA10PT(-EC)
1.5 - 4.8 µm PbSe - FDPSE2X2 - - PDA20H(-EC)
2.0 - 5.4 µm HgCdTe (MCT) - - - - PDA10JT(-EC)
2.0 - 8.0 µm HgCdTe (MCT) VML8T0
VML8T4 d
- - - PDAVJ8
2.0 - 10.6 µm HgCdTe (MCT) VML10T0
VML10T4 d
- - - PDAVJ10
2.7 - 5.0 µm HgCdTe (MCT) VL5T0 - - - PDAVJ5
2.7 - 5.3 µm InAsSb - - - - PDA07P2
  • Calibrated Unmounted Photodiode
  • Unmounted TO-46 Can Photodiode
  • Unmounted TO-46 Can Photodiode with FC/PC Bulkhead
  • Photovoltaic Detector with Thermoelectric Cooler

HgCdTe (MCT) Amplified Photodetectors, Switchable Gain

Item #a,b Housing
Featuresc
Wavelength
Range (λP)
Responsivity ×
Effective Detector
Width @ λP
Responsivity
@ λP
Output
Bandwidth
@ 3 dB
Conversion
Gain @ λP
NEPd Typical
Performance
Graphse
PDAVJ8 2.0 - 8.0 µm
(6.5 µm)
≥0.04 A·mm/Wf - DC - 100 MHzg 185 V/W (Gain Setting 1)
6000 V/W (Gain Setting 8)
170 pW/Hz1/2 More Info
PDAVJ10 2.0 - 10.6 µm
(6.5 µm)
≥0.01 A·mm/Wf - DC - 100 MHzg 120 V/W (Gain Setting 1)
4000 V/W (Gain Setting 8)
210 pW/Hz1/2 More Info
PDAVJ5 2.7 - 5.0 µm
(4.75 µm)
- ≥1 A/W DC - 1 MHzh 1500 V/W (Gain Setting 1)
200 000 V/W (Gain Setting 8)
14 pW/Hz1/2 More Info
  • Click on the links to view photos of the items.
  • More detailed specifications are available in the Specs tab.
  • Click the diagrams for details of the housing.
  • Minimum Noise Equivalent Power; Specified from DC to Cut-Off Frequency
  • Click the icons for responsivity, detectivity, and frequency response graphs.
  • Due to the multilayer construction of the sensor chips used in these detectors, the responsivity is inseparable from the sensor width.
  • Independent of Gain Step
  • Specified at Gain Step 1; Bandwidth Varies with Each Gain Step
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available
PDAVJ8 Support Documentation
PDAVJ8HgCdTe Amplified Photodetector, 2.0 - 8.0 µm, DC - 100 MHz BW, 1 mm2, 100 - 120 or 220 - 240 VAC
$2,990.00
Today
PDAVJ10 Support Documentation
PDAVJ10HgCdTe Amplified Photodetector, 2.0 - 10.6 µm, DC - 100 MHz BW, 1 mm2, 100 - 120 or 220 - 240 VAC
$3,520.00
Today
PDAVJ5 Support Documentation
PDAVJ5NEW!HgCdTe Amplified Photodetector, 2.7 - 5.0 µm, DC - 1 MHz BW, 1 mm2, 100 - 120 or 220 - 240 VAC
$1,823.00
Today
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