Free-Space InAsSb Amplified Detector with TEC

  • Broadband Wavelength Sensitivity: 1.0 - 5.8 µm
  • Built-In TEC Lowers Thermal Noise
  • 8-Step Variable Gain and Bandwidth


Post Not Included

Side Mounted,
Post Not Included

Side View

Power Supply
Included with

Related Items

Please Wait
MIR Detector Selection Guidea
Item # (Detector) Detector Type Wavelength
PDA10DT (InGaAs) Photodiode 0.9 - 2.57 µm 1,000 kHz Yes
PDA10D2 (InGaAs) Photodiode 0.9 - 2.6 µm 25,000 kHz No
PDA10PT (InAsSb) Photodiode 1.0 - 5.8 µm 1,600 kHz Yes
PDA07P2 (InAsSb) Photodiode 2.7 - 5.3 µm 9 MHz No
PDAVJ8 (HgCdTe) Photodiode 2.0 - 8.0 µm 100 MHz No
PDAVJ10 (HgCdTe) Photodiode 2.0 - 10.6 µm 100 MHz No
PDAVJ5 (HgCdTe) Photodiode 2.7 - 5.0 µm 1 MHz No
PDA13L2 (LiTaO3) Pyroelectric 0.6 - 16 µm 10 kHz No
  • See the Cross Reference tab for our full selection of photodetectors.


  • Sensitive to Mid-IR (MIR) Light from 1.0 - 5.8 µm
  • Max Bandwidth of Detector Package: 1600 kHz
  • Built-In Thermoelectric Cooler Improves Sensitivity
  • Ø1 mm Detector Element
  • Post Mountable in Two Orientations
  • Internally SM1 (1.035"-40) Threaded
  • Location-Specific Power Adapter Included

Thorlabs' PDA10PT(-EC) Amplified Detector is a thermoelectrically cooled photoconductive InAsSb (indium arsenide antimonide) detector. Like our HgCdTe (MCT) detector, this material is sensitive to light in the mid-IR spectral range, but the PDA10PT features a broader sensitivity range of 1.0 to 5.8 µm. Two rotary switches control the gain amplifier and detector package bandwidth, allowing performance to be optimized for a variety of applications. The gain switch features eight discrete steps from 0 - 40 dB, while the bandwidth switch provides eight discrete steps from 12.5 kHz - 1600 kHz. The thermoelectric cooler (TEC) uses a thermistor feedback loop to hold the temperature of the detector element at -30 °C, minimizing thermal contributions to the output signal.

For best results, we recommend connecting the BNC output cable (not included) to a 50 Ω termination. Because the detector is AC coupled, it requires a pulsed or chopped input signal. AC-coupled detectors will not see unchopped CW light because they are only sensitive to intensity changes, not absolute intensity. These photodetectors are ideal for use with Thorlabs' passive low-pass filters; these filters have a 50 Ω input and a high-impedance output that allows them to be directly attached to high-impedance measurement devices such as an oscilloscope.

PDA10PT Side View
Click to Enlarge

Side View Showing Gain and Bandwidth Adjusters
PDA10PT Top View
Click to Enlarge

Top View Showing Signal Output and Power Input

The detector package incorporates many of the same mechanical features as our other mounted photodetectors. An internal SM1 (1.035"-40) threading allows Ø1" lens tubes to be mounted in front of the detector element. Two 8-32 (M4 in the -EC version) tapped holes connect a Ø1/2" post to the housing in one of two perpendicular orientations, as shown in the image at the top of the page. The PDA10PT(-EC) includes a 100 - 240 VAC power adapter. If you require a different adapter plug, please contact Tech Support prior to ordering. An SM1RR Retaining Ring is also included.

Please note that inhomogeneities at the edges of the active area of the detector can generate unwanted capacitance and resistance effects that distort the time-domain response of the output. Thorlabs therefore recommends that the incident light is well centered on the active area. The SM1 (1.035"-40) threading on the housing can be connected to an SM1 lens tube; the lens tube can be used to mount an iris or pinhole in front of the detector element. Because the detector package protrudes 3.9 mm beyond the front of the threading, optics and optomechanics cannot be attached directly to the housing.

In addition to the InAsSb detector sold here, Thorlabs offers room-temperature amplified photodetectors.

All values given below are for a 50 Ω load, unless otherwise stated.

Gain (High Z)c
0 dB 100 V/A
4 dB 160 V/A
10 dB 320 V/A
16 dB 630 V/A
22 dB 1260 V/A
28 dB 2510 V/A
34 dB 5010 V/A
40 dB 10 000 V/A

c. The gain for a 50 Ω impedance is one-half of the gain for high Z.

Noise-Equivalent Power (NEP) Valuesd
Gain NEP
0 dB 1.91 × 10-9 W/Hz1/2
4 dB 1.21 × 10-9 W/Hz1/2
10 dB 6.24 × 10-10 W/Hz1/2
16 dB 3.48 × 10-10 W/Hz1/2
22 dB 2.27 × 10-10 W/Hz1/2
28 dB 1.83 × 10-10 W/Hz1/2
34 dB 1.63 × 10-10 W/Hz1/2
40 dB 1.49 × 10-10 W/Hz1/2

d. Measured at λP with a 1600 kHz bandwidth and a 50 Ω impedance.

Item # PDA10PT(-EC)
Optical Specifications
Wavelength Range 1.0 - 5.8 μm
Peak Wavelength (λP) 4.9 μm
Peak Responsivity 0.8 A/W (Min) at Peak Wavelength
1.6 A/W (Typ.) at Peak Wavelength
Electrical Specifications
Gain Adjustment Range 40 dB
Gain Settings 0, 4, 10, 16, 22, 28, 34, 40 dB
(8 Steps)
Bandwidth Settings 12.5, 25, 50, 100, 200, 400, 800, or 1600 kHz
(8 Steps)
Output Voltagea 0 - 5 V at 50 Ω
0 - 10 V at High Z
Output Impedance 50 Ω
Output Current 100 mA (Max)
Load Impedance 50 Ω to High Z
Output Offsetb 20 mV (Typ.)
45 mV (Max)
Offset Drift 2.7 mV/°C (at 40 dB Gain)
TEC Temperature -30 °C
Physical Specifications
Detector Element InAsSb
Window Material Sapphire
Active Area Ø1 mm
Surface Depth 0.12" (3.1 mm)
Output BNC
Detector Size 3" × 2.2" × 2.2"
(76.2 mm × 55.9 mm × 55.9 mm)
Weight Detector: 0.42 lbs (191 g)
Power Supply: 0.82 lbs (372 g)
Power Supply 30 W, Location-Specific
Power Cord Included
Input Power 100 - 240 VAC, 50 - 60 Hz
Storage Temperature 0 to 60 °C
Operating Temperature 0 to 30 °C
  • Saturation of the output voltage may cause damage to the InAsSb detector element.
  • Offset after the temperature has stabilized at each gain step. The worst-case offset is for the 40 dB gain step.
PDA10PT Wavelength Sensitivity
Click to Enlarge

Click Here for Raw Data
The graph above is for the 0 dB gain setting.
PDA10PT Bandwidth
Click to Enlarge

Click Here for Raw Data
PDA10PT Noise Comparison
Click to Enlarge

These traces compare the noise level for the lowest gain and bandwidth settings to the noise level for the highest gain and bandwidth settings.


PDA10PT Detectivity
Click to Enlarge

The graph above is for the 0 dB gain setting.

Detectivity, D*, is defined as:

Detectivity Equation

where A is the area of the photosensitive region of the detector, Δf is the effective noise bandwidth, and NEP is the noise-equivalent power. For the PDA10PT,

Detectivity Equation

For more information, please see the manual.

Output Signal

BNC Female

BNC Female

0 - 5 V at 50 Ω
0 - 10 V at High Z
100 mA Max Current

Power Input

4-Pin Female

BNC Female
1-12 V
3+5 V
4+12 V

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 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

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).

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.)

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.

Material Dark Current Speed Spectral Range Cost
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 input signal power that results in a signal-to-noise ratio (SNR) of 1 in a 1 Hz output bandwidth. 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:
Martin Silies  (posted 2024-04-04 12:05:30.943)
Dear Thorlabs team, I am highly interested in the InAsSb Amplified Detector with TEC. We plan to characterize our femtosecond laser source that is emitting light in the NIR to mid-IR spectral region. The spectral range is ranging from 1000nm to 2300nm. In detail, we want to implement the APD in a home-built Fourier-transform spectrometer in order to characterize the spectrum of the FemtoFiber SCIR laser. The laser is a pulsed source emitting pulses at a repetition rate of 40MHz (pulse duration in the ps regime due to nonlinear processes). The signal from the APD should later be fed into a PC via Analog-to-Digital Converter and the voltage from the APD should be recorded as a function of position in a Fourier-Transform spectrometer. I am curious about the signal I would see on an oscilloscope. The bandwith of the APD is relatively narrow, hence the response time of the APD is long, right? Would I hence only see a constant voltage signal, when the repetition rate of my laser is 40MHz? Many thanks for your answer in advance, Martin Silies
ksosnowski  (posted 2024-04-22 02:56:53.0)
Hello Martin, thanks for reaching out to Thorlabs. Picosecond pulses themselves are beyond the 1600kHz max bandwidth of the APD, and the 40MHz repetition rate is as well. There will be some effective lowpass attenuation of the signal due to this. Essentially these pulses turn off faster than the system's rise time, so their peak value is never seen at the output. Because the repetition rate is faster than the time-limited response of the detector, these pulses will blur together to form an average, though attenuated, and will give an effectively constant output due to this. PDA10PT is not based on avalanche photodiode however we do also have some temperature controlled InGaAs APDs like our APD430C. I have reached out directly to discuss your application in further detail.

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

Photodetector Cross Reference
Wavelength Material Unmounted
Amplified Detector,
OEM Package
200 - 1100 nm Si FDS010 SM05PD2A
Si - SM1PD2A - - -
240 - 1170 nm B-Si - - DET20X2 - -
320 - 1000 nm Si - - - PDA8A2 -
320 - 1100 nm Si FD11A SM05PD3A - PDF10A2 -
Si - a - DET100A2 a PDA100A2 a PDAPC2 a
340 - 1100 nm Si FDS10X10 - - - -
350 - 1100 nm Si FDS100
FDS100-CAL b
Si FDS1010
FDS1010-CAL b
- - -
400 - 1000 nm Si - - - PDA015A2
400 - 1100 nm Si FDS015 c - - - -
Si FDS025 c
FDS02 d
- DET02AFC(/M)
- -
400 - 1700 nm Si & InGaAs DSD2 - - - -
500 - 1700 nm InGaAs - - DET10N2 - -
0.6 - 16 µm LiTaO3 - - - PDA13L2e -
750 - 1650 nm InGaAs - - - PDA8GS -
800 - 1700 nm InGaAs FGA015 - - PDA015C2 -
InGaAs FGA21
InGaAs FGA01 c
- DET01CFC(/M) - -
InGaAs FDGA05 c - - PDA05CF2 PDAPC6
InGaAs - - DET08CFC(/M)
- -
InGaAs - - - PDF10C2 -
800 - 1800 nm Ge FDG03
SM05PD6A DET30B2 PDA30B2 -
Ge FDG05 - - - -
900 - 1700 nm InGaAs FGA10 SM05PD4A DET10C2 PDA10CS2 -
900 - 2600 nm InGaAs FD05D - DET05D2 - -
950 - 1650 nm InGaAs - - - FPD310-FC-NIR
1.0 - 5.8 µm InAsSb - - - PDA10PT(-EC) -
2.0 - 8.0 µm HgCdTe (MCT) VML8T0
VML8T4 f
- - PDAVJ8 -
2.0 - 10.6 µm HgCdTe (MCT) VML10T0
VML10T4 f
- - PDAVJ10 -
2.7 - 5.0 µm HgCdTe (MCT) VL5T0 - - PDAVJ5 -
2.7 - 5.3 µm InAsSb - - - PDA07P2 PDAPC9
  • If you are interested in purchasing the bare photodiode incorporated in these detectors without the printed circuit board, please contact Tech Support.
  • Calibrated Unmounted Photodiode
  • Unmounted TO-46 Can Photodiode
  • Unmounted TO-46 Can Photodiode with FC/PC Bulkhead
  • Pyroelectric Detector
  • Photovoltaic Detector with Thermoelectric Cooler
Back to Top

InAsSb Detector with TEC: 1.0 - 5.8 µm

Item # PDA10PT(-EC)
Click Image to Enlarge PDA10JT
Detector Element
(Click for Image)
Wavelength Range 1.0 - 5.8 µm
Peak Wavelength (λP) 4.9 µm
Peak Responsivity 0.8 A/W (Min) at λP
1.6 A/W (Typ.) at λP
Active Area Ø1 mm
Window Material Sapphire
Gain Settings 8 Steps: 0, 4, 10, 16,
22, 28, 34, or 40 dB
Bandwidth Settings 8 Steps from 12.5 kHz to 1600 kHz
Noise-Equivalent Power (NEP) 1.49 x 10-10 W/Hz1/2
(for 40 dB Gain and
1600 kHz Bandwidth)

More detailed specifications are available in the Specs tab.

  • Sensitive to Chopped or Pulsed Mid-IR Light from 1.0 µm to 5.8 µm
  • Detector is Cooled to -30 °C to Reduce Thermal Noise
  • Ø1 mm Active Area
  • Variable Gain Amplifier (100 V/A to 10 000 V/A)
  • Variable Bandwidth (12.5 kHz to 1600 kHz)
  • Internal SM1 (1.035"-40) Threading
  • Location-Specific Power Adapter Included
PDA10PT Wavelength Sensitivity
Click to Enlarge
Click Here for Raw Data
The graph above is for the 0 dB gain setting.
PDA10PT Bandwidth
Click to Enlarge
Click Here for Raw Data
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Imperial Price Available
PDA10PT Support Documentation
PDA10PTInAsSb Amplified Detector with TEC, 1.0 - 5.8 µm, AC-Coupled Amplifier, Ø1 mm, 100 - 240 VAC
+1 Qty Docs Part Number - Metric Price Available
PDA10PT-EC Support Documentation
PDA10PT-ECInAsSb Amplified Detector with TEC, 1.0 - 5.8 µm, AC-Coupled Amplifier, Ø1 mm, 100 - 240 VAC
Last Edited: Jul 25, 2013 Author: Dan Daranciang