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InGaAs Transimpedance Amplified Photodetectors

  • InGaAs Transimpedance Amplified Detector
  • Fixed Switchable Amplified Detectors with Output up to 10 V
  • Wavelength Range from 800 - 2600 nm





Detector with Ø1" Lens
Tube Attached to a 30 mm
Cage System

Power Supply
Included with

Related Items

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MIR Photodetector Selection Guidea
Item # (Detector) Wavelength
PDA10DT (InGaAs) 0.9 - 2.57 µm 1,000 kHz Yes
PDA30G (PbS) 1.0 - 2.9 µm 1 kHz No
PDA10PT (InAsSb) 1.0 - 5.8 µm 1,600 kHz Yes
PDA10D (InGaAs) 1.2 - 2.6 µm 15,000 kHz No
PDA20H (PbSe) 1.5 - 4.8 µm 10 kHz No
PDA10JT (HgCdTe) 2.0 - 5.4 µm 160 kHz Yes
  • See the Cross Reference tab for our full selection of photodetectors.
Removable Internal SM1 Adapter
Click to Enlarge

Each detector has an internal SM05 and external SM1 thread and comes with an
attached SM1T1 Internal SM1 Adapter
and SM1RR Retaining Ring.


  • Wavelength Ranges from 800 to 2600 nm
  • Low-Noise, Wide Band Amplifiers
  • Fixed and Switchable Gain Modules
  • PDF10C Sensitive Down to Femtowatt Powers
  • 0 to 10 V Output
  • Compatible with SM1 (1.035"-40) Series and Some SM05 (0.535"-40) Series Products
  • Linear Power Supply Included
photo detector power supply
Click to Enlarge

The power supply is included with all of the detectors on this page.

These InGaAs Transimpedance Amplified Photodetectors, which consist of a photodiode and amplifier in a compact, low-profile package, are sensitive to light in the NIR region from 800 nm to 2600 nm. The slim profile housing enables use in light paths with space constraints. All connections and controls are located perpendicular to the light path, providing increased accessibility. Amplification is provided by low noise transimpedance or voltage amplifiers that are capable of driving 50 Ω loads. Signal output is via a BNC connector, making these detectors 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. Thorlabs offers a wide variety of BNC, BNC-to-SMA, and SMC cables, as well as a variety of BNC, SMA, and SMC adapters.

Each housing provides two 8-32 tapped mounting holes (M4 for - EC) centered on the detector surface for vertical or horizontal post mounting. The housings also feature external SM1 threading and internal SM05 threading that are compatible with most Thorlabs SM1 (1.035"-40)- and SM05 (0.535"-40)-threaded accessories. Additionally, an internally threaded SM1 coupler is included with each detector. This allows convenient mounting of SM1 compatible accessories, optics, and cage assembly accessories. SM1-threaded fiber adapters, available below, may be used with any of these detectors. The S120-FC FC/PC internally SM1-threaded fiber adapter is not compatible. For an FC/PC adapter compatible with these detectors, use the SM1FC externally SM1-threaded adapter. Externally SM1-threaded adapters, available below, should be mated to the included internally SM1-threaded adapter, while internally SM1-threaded adapters can be mated directly to the housing. The internal SM05 threading is only suitable for mating to an externally threaded SM05 lens tube (components such as fiber adapters cannot be threaded onto the SM05 threading). 

A 120 VAC AC/DC linear power supply (230 VAC for -EC versions) is included with each photodetector. Due to limitations in the IC, the high-speed amplifier used in these devices may become unstable, exhibiting oscillations or negative output if the linear power supply voltage is applied when the module is on. The unit should always be powered up using the power switch on the power supply or the unit itself. Hot plugging the unit is not recommended. Additionally, 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 photodetector output. Thorlabs therefore recommends that the incident light on the photodetector is well centered on the active area. The SM1 (1.035"-40) threading on the housing is ideally suited for mounting a Ø1" focusing lens or pinhole in front of the detector element. 

Performance Specifications

Item #Detector
Active AreaWavelengthPeak
BandwidthNoise Equivalent Power
Rise Time
PDA20C InGaAs 3.14 mm2
(Ø2.0 mm)
800 - 1700 nm 1 A/W
@ 1550 nm
DC - 5 MHz 22 x 10-12 W/Hz1/2 70 ns b
PDA10CF 0.2 mm2
(Ø0.5 mm)
800 - 1700 nm 1.04 A/W
@ 1590 nm
DC - 150 MHz 1.2 x 10-11 W/Hz1/2 2.3 ns b
PDA20CS 3.14 mm2
(Ø2.0 mm)
800 - 1700 nm 1.04 A/W
@ 1590 nm
DC - 10 MHz 1.14 x 10-12 -
5.12 x 10-11 W/Hz1/2
N/A c
PDA10CS 0.8 mm2
(Ø1.0 mm)
900 - 1700 nm 1.05 A/W
@ 1550 nm
DC - 17 MHz 1.25 x 10-12 -
6.0 x 10-11 W/Hz1/2
N/A c
PDA10D 0.8 mm2
(Ø1.0 mm)
1.2 - 2.6 µm 1.35 A/W
@ 2.3 µm
DC - 15 MHz 3.5 x 10-11 W/Hz1/2 23.3 ns b
PDF10C 0.2 mm2
(Ø0.5 mm)
800 - 1700 nm 1.0 A/W
@ 1550 nm
DC - 25 Hz 7.5 x 10-15 W/Hz1/2 19 ms b
  • An NEP range is given for the switchable gain detectors, a max NEP is given for the fixed gain detectors.
  • Please note that rise time is specified at the peak responsivity wavelength.
  • Rise times depend on the chosen gain level and wavelength. As one increases the gain of a given optical amplifier, the bandwidth is reduced, and hence, the rise time increases. Please refer to the photodiode tutorial for information on calculating the rise time. Bandwidth specifications for each adjustable photodetector may be found in the table below.

Gain Specifications

Item #Gain TypeGain w/ Hi-Z LoadGain w/ 50 Ω LoadOutput Voltage
w/ Hi-Z Load
Output Voltage
w/ 50 Ω Load
PDA20C Fixed 500 kV/A 175 kV/A 0 to 10 V 0 to 3.6 V
PDA10CF 10 kV/A 5 kV/A 0 to 10 V 0 to 5 V
PDA10D 10 kV/A 5 kV/A 0 to 10 V 0 to 5 V

Item #Gain StepGain
w/ Hi-Z Load
w/ 50 Ω Load
NEPbOffsetOutput Voltage
w/ Hi-Z Load
Output Voltage
w/ 50 Ω Load
PDA20CS 0 1.51 kV/A 0.75 kV/A 10 MHz 365 µV 5.12 x 10-11 W/Hz1/2 5 mV (10 mV Max) 0 to 10 V 0 to 5 V
10 4.75 kV/A 2.38 kV/A 4 MHz 500 µV 3.11 x 10-11 W/Hz1/2 6 mV (10 mV Max)
20 15 kV/A 7.5 kV/A 1.87 MHz 340 µV 6.54 x 10-12 W/Hz1/2 6 mV (10 mV Max)
30 47.5 kV/A 23.8 kV/A 660 kHz 490 µV 3.04 x 10-12 W/Hz1/2 6 mV (10 mV Max)
40 151 kV/A 75 kV/A 200 kHz 590 µV 1.14 x 10-12 W/Hz1/2 6 mV (10 mV Max)
50 475 kV/A 238 kV/A 67 kHz 670 µV 2.91 x 10-12 W/Hz1/2 6 mV (10 mV Max)
60 1.5 MV/A 0.75 MV/A 25 kHz 880 µV 1.76 x 10-12 W/Hz1/2 6 mV (10 mV Max)
70 4.75 MV/A 2.38 MV/A 4 kHz 1.33 mV 5.89 x 10-12 W/Hz1/2 8 mV (12 mV Max)
PDA10CS 0 1.51 kV/A 0.75 kV/A 17 MHz 600 µV 6.0 x 10-11 W/Hz1/2 5 mV (10 mV Max) 0 to 10 V 0 to 5 V
10 4.75 kV/A 2.38 kV/A 8.5 MHz 320 µV 1.0 x 10-11 W/Hz1/2 6 mV (12 mV Max)
20 15 kV/A 7.5 kV/A 1.9 MHz 310 µV 3.0 x 10-12 W/Hz1/2 6 mV (15 mV Max)
30 47.5 kV/A 23.8 kV/A 775 kHz 300 µV 1.25 x 10-12 W/Hz1/2 8 mV (15 mV Max)
40 151 kV/A 75 kV/A 320 kHz 300 µV 1.4 x 10-12 W/Hz1/2 10 mV (20 mV Max)
50 475 kV/A 238 kV/A 90 kHz 475 µV 1.5 x 10-12 W/Hz1/2 15 mV (40 mV Max)
60 1.5 MV/A 0.75 MV/A 33 kHz 850 µV 1.5 x 10-12 W/Hz1/2 20 mV (75 mV Max)
70 4.75 MV/A 2.38 MV/A 12 kHz 1.5 mV 2.0 x 10-12 W/Hz1/2 20 mV (200 mV Max)
  • Gain figures can also be expressed in units of Ω.
  • The Noise Equivalent Power is specified at the peak wavelength.
PDA Series Compact Design
PDA Series Design, scale in inches [mm ].

Compact PDA & PDF Series Design

Thorlabs' Amplified Photodiode series features a slim design, which allows the detector access to the light path even between closely spaced optical elements.

The power supply input and the BNC output are located on the same outer edge of the package, further reducing the device thickness and allowing easier integration into tight optic arrangements. The PDA and PDF series detectors can fit into spaces as thin as 0.83" (21.1 mm) when the SM1 coupler is removed. With the SM1 coupler attached, the smallest width the detector can fit into is 1.03" (26.2 mm).

Additionally, the detectors have two tapped mounting holes perpendicular to each other so that the unit can be mounted in a horizontal or vertical orientation. This dual mounting feature offsets the fact that the cables protrude out the side of the package, thus requiring more free space above or alongside your beam path.

The switchable gain detectors feature an eight-position rotary gain switch (pictured below right) mounted on an outside edge perpendicular to the power supply and BNC output connections. The location of the gain switch allows for easy adjustments while the detector is mounted.

PDA Detector Bottom and Side View

PDA Series Mounting Options

The PDA series of amplified photodetectors are compatible with our entire line of lens tubes, TR series posts, and cage mounting systems. Because of the wide range of mounting options, the best method for mounting the housing in a given optical setup is not always obvious. The pictures and text in this tab will discuss some of the common mounting solutions. As always, our technical support staff is available for individual consultation.

 amplified photodetector  amplified photodetector disassembled  amplified photodetector close up
Picture of a PDA series photodetector as it will look when unpackaged. Picture of a DET series photodetector with the included SM1T1 and its retaining ring removed from the front of the housing. Thorlabs' PDA series photodetectors feature the same mounting options. A close up picture of the front of the PDA10A photodetector. The internal SM1 threading on the SM1T1 adapter and internal SM05 threading on the photodetector housing can be seen in this image.

TR Series Post (Ø1/2" Posts) System

The PDA housing can be mounted vertically or horizontally on a TR Series Post using the 8-32 (M4) threaded holes.

 mounted amplified photodetector vertical  mounted amplified photodetector horizontal
DET series photodetector mounted vertically on a TR series post. In this configuration, the output and power cables (PDA series) are oriented vertically and away from the optic table, facilitating a neater optical setup. PDA series photodetector mounted horizontally on a TR series post. In this configuration, the on/off switch is conveniently oriented on the top of the detector.

Lens Tube System

Each PDA housing includes a detachable Ø1" Optic Mount (SM1T1) that allows for Ø1" (Ø25.4 mm) optical components, such as optical filters and lenses, to be mounted along the axis perpendicular to the center of the photosensitive region. The maximum thickness of an optic that can be mounted in the SM1T1 is 0.1" (2.8 mm). For thicker Ø1" (Ø25.4 mm) optics or for any thickness of Ø0.5" (Ø12.7 mm) optics, remove the SM1T1 from the front of the detector and place (must be purchased separately) an SM1 or SM05 series lens tube, respectively, on the front of the detector.

The SM1 and SM05 threadings on the PDA photodetector housing make it compatible with our SM lens tube system and accessories. Two particularly useful accessories include the SM-threaded irises and the SM-compatible IR and visible alignment tools. Also available are fiber optic adapters for use with connectorized fibers.

 Lens tube mounted amplified photodetector
DET series photodetector mounted onto an SM1L30C Ø1" Slotted Lens Tube, which is housing a focusing optic. The lens tube is attached to a 30 mm cage system via a CP02 SM1-Threaded 30 mm Cage Plate. This arrangement allows easy access for optic adjustment and signal alignment.

Cage System

The simplest method for attaching the PDA photodetector housing to a cage plate is to remove the SM1T1 that is attached to the front of the PDA when it is shipped. This will expose external SM1 threading that is deep enough to thread the photodetector directly to a CP02 30 mm cage plate. When the CP02 cage plate is tightened down onto the PDA photodetector housing, the cage plate will not necessarily be square with the detector. To fix this, back off the cage plate until it is square with the photodetector and then use the retaining ring included with the SM1T1 to lock the PDA photodetector into the desired location.

This method for attaching the PDA photodetector housing to a cage plate does not allow much freedom in determining the orientation of the photodetector; however, it has the benefit of not needing an adapter piece, and it allows the diode to be as close as possible to the cage plate, which can be important in setups where the light is divergent. As a side note, Thorlabs sells the SM05PD and SM1PD series of photodiodes that can be threaded into a cage plate so that the diode is flush with the front surface of the cage plate; however, the photodiode is unbiased.

For more freedom in choosing the orientation of the PDA photodetector housing when attaching it, a SM1T2 lens tube coupler can be purchased. In this configuration the SM1T1 is left on the detector and the SM1T2 is threaded into it. The exposed external SM1 threading is now deep enough to secure the detector to a CP02 cage plate in any orientation and lock it into place using one of the two locking rings on the ST1T2.

 photodetector with cage plate

photodetector with cage plate

photodetector with cage plate and spacer

This picture shows a DET series photodetector attached to a CP02 cage plate after removing the SM1T1. The retaining ring from the SM1T1 was used to make the orientation of the detector square with the cage plate. These two pictures show a DET series photodetector in a horizontal configuration. The top picture shows the detector directely coupled to a CP02 cage plate.
The bottom picture shows a DET series photodetector attached to a CP02 cage plate using an SM1T2 adapter in addition to the SM1T1 that comes with the PDA series detector.

Although not pictured here, the PDA photodetector housing can be connected to a 16 mm cage system by purchasing an SM05T2. It can be used to connect the PDA photodetector housing to an SP02 cage plate.


The image below shows a Michelson Interferometer built entirely from parts available from Thorlabs. This application demonstrates the ease with which an optical system can be constructed using our lens tube, TR series post, and cage systems. A PDA series photodetector is interchangable with the DET series photodetector shown in the picture.

 Michelson interferometer

The table below contains a part list for the Michelson Interferometer for use in the visible range. Follow the links to the pages for more information about the individual parts. 

Item #QuantityDescriptionItem #QuantityDescription
KC1 1 Mirror Mount CT1 1 1/2" Travel Translator
BB1-E02 2 Broadband Dielectric Laser Mirrors SM1D12 1 SM1 Threaded Lens Tube Iris
ER4 8 4" Cage Rods SM1L30C 1 SM1 3" Slotted Lens Tube
ER6 4 6" Cage Rods SM1V05 1 Ø1" Adjustable Length Lens Tube
CM1-BS013 1 Cube-Mounted Beamsplitter CP08FP 1 30 mm Cage Plate for FiberPorts
BA2 1 Post Base (not shown in picture) PAF-X-5-A 1 FiberPort
TR2 1 Ø1/2" Post, 2" in Length P1-460B-FC-2 1 Single Mode Fiber Patch Cable
PH2 1 Ø1/2" Post Holder DET36A / PDA36A 1 Biased / Amplified Photodiode Detector

BNC Female Output (Photodetector)

BNC Female

0 - 10 V Output

PDA Male (Power Cables)

Pinout for PDA Power Cable

PDA Female (Photodetector)

Pinout for PDA Power Connector

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 DET25K PDA25K
200 - 1100 nm Si FDS010 - SM05PD2A
Si - - SM1PD2A - -
320 - 1100 nm Si - - - - PDA8A
Si - - - - PDF10A
Si - - - - PDA100A
340 - 1100 nm Si FDS10X10 - - - -
350 - 1100 nm Si FDS100
FDS100-CAL a
- SM05PD1A
Si FDS1010
FDS1010-CAL a
400 - 1100 nm Si FDS025 b
FDS02 c
- - DET02AFC
400 - 1700 nm Si & InGaAs DSD2 - - - -
500 - 1700 nm InGaAs - - DET10N - -
800 - 1700 nm InGaAs FGA21
- SM05PD5A - PDA20C
InGaAs FGA01 b
- - DET01CFC -
InGaAs FDGA05 - - - PDA10CF
InGaAs - - - DET08CFC
InGaAs - - - DET20C -
800 - 1800 nm Ge FDG03
Ge FDG50 - - DET50B PDA50B
Ge FDG05
- - - -
800 - 2600 µm InGaAs FD05D - - DET05D -
FD10D - - DET10D -
900 - 1700 nm InGaAs FGA10 - SM05PD4A DET10C PDA10CS
1.0 - 2.9 µm PbS - FDPS3X3 - - PDA30G
1.0 - 5.8 µm InAsSb - - - - PDA10PT
1.2 - 2.6 µm InGaAs - - - - PDA10D
1.5 - 4.8 µm PbSe - FDPSE2X2 - - PDA20H
2.0 - 5.4 µm HgCdTe (MCT) - - - - PDA10JT
  • Calibrated Unmounted Photodiode
  • Unmounted TO-46 Can Photodiode
  • Unmounted TO-46 Can Photodiode with FC/PC Bulkhead

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

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.

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

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Posted Comments:
Posted Date:2016-05-04 14:01:19.97
Hello, we use this photodiode for two-photon absorption. Can you tell me of which material the front window is?
Posted Date:2016-05-05 10:21:11.0
Response from Bweh at Thorlabs USA: The window material for the PDA10D is borosilicate.
Posted Date:2015-06-02 17:40:49.587
Dear ladies and gentleman. I think the PDF10CF is really a great product and the price compared to the biased version is what it makes even more great. Unfortunately in our application (interferometry) we would need an AC-coupled version. Would it be possible to add such a version in your portfolio? Best Regards Bernhard Reitinger
Posted Date:2015-06-05 09:39:33.0
Response from Jeremy at Thorlabs: Thank you very much for the feedback. We will look into offering the AC-coupled version or offer it as a special. We will contact you directly about this.
Posted Date:2015-04-10 11:21:38.703
The Adapter doesn't show the green light and I guess the current is not passing through it. Can you please help me with this issue
Posted Date:2015-04-14 09:57:47.0
Response from Jeremy at Thorlabs: Please make sure the voltage selection switch is set to the correct setting. It could also be that the fuse is blown. I will contact you directly to troubleshoot more about this.
Posted Date:2015-02-02 16:36:14.25
Are the bandwidths quoted single-sided or double-sided ? Thank you
Posted Date:2015-02-03 03:58:43.0
Response from Jeremy at Thorlabs: These are measured from DC so it should be single-sided.
Posted Date:2014-05-09 13:04:28.943
We are using multiple numbers of this product (40) in an AWG. A power supply to power multiple units would be a great help. Controling mains leads to 40 power supplys is horid
Posted Date:2014-06-11 10:32:30.0
Response from Jeremy at Thorlabs: Thank you for contacting Thorlabs. We will look into the possibility of providing this custom power supply for you and contact you directly.
Posted Date:2012-09-06 09:45:57.0
Hello I recently bought a PDA36A with the intention of measuring current due to light radioluminescence. I connected a photodiode PDA36A to an electrometer and I measured a noise about 150 nA. Is this normal? PDA36A noise is higher than DET36A?
Posted Date:2012-08-09 10:28:00.0
Response from Jeremy at Thorlabs: Using the SolidWorks, the typical FOV for the different PDA is listed below. PDA100A: 53.13°, PDA36A: 70.19°, PDA10A: 122.92°, PDF10A: 127.81°, PDF8A: 150.64°.
Posted Date:2012-07-31 17:34:45.0
Dear, Is it possible to provide me with the Field of View (FOV) of following Thorlabs Amplified Si detectors: PDA10A PDA8A PDF10A PDA36A PDA100A Many thanks and best regards, Ben Aernouts Department Biosystems, Division MeBioS KULeuven
Posted Date:2012-05-15 09:49:00.0
Response from Tim at Thorlabs: Thank you for your feedback! Our superseded products can be found by utilizing the search bar where the original supporting documentation is left intact. I am not sure that the part number you specified was our original part number. I will send you an overview of the old web presentation in order to determine the part number and provide supporting documentation for the correct product.
Posted Date:2012-05-11 18:54:17.0
Is the "New vs. Old" page mentioned in the older comments no longer on this site? I am looking for information on an old PDA-50 Si Amplified Photodetector
Posted Date:2012-01-25 15:15:00.0
Response from Buki at Thorlabs: We specify at least +/- 12V, 125mA. However this is very conservative, especially if the PDA is driving a high impedance load. Most of the current usage is for driving the output. A 50Ohm load with the maximum output voltage (5V) will require a current of 100mA (5V/50Ohms). The amplifier itself uses approximately +/- 25mA from +/-12V supplies. The +12V supply needs to be able to supply an additional 100mA if it is driving a 50Ohm load. Please contact if you have any questions.
Posted Date:2012-01-25 10:37:37.0
Could you advise what current the device draws at +/- 12V if we want to use our own power supply?
Posted Date:2010-11-08 10:01:42.0
Response from Javier at Thorlabs to Nathan: Thank you for your feedback. The PDA10CF and PDA10CS detectors have not been superseded. We are currently working with our web team to reactivate the shopping cart option so that you can order them through the web. You can also contact our sales department st or by phone at (973) 579 7227 to place an order.
Posted Date:2010-11-08 08:50:43.0
Have you discontinued the PDA10CF & PDA10CS detectors? They are still included in the overview and specs tabs, but I cant find more detailed information or an option for purchasing? Or is there a replacement part (particularly for the variable gain version, but also for the fixed gain/high bandwidth version)? Thanks.
Posted Date:2010-11-04 18:21:38.0
Response from Javier at Thorlabs to imag: all of our photodiodes have a protective resin or coating. In order to remove dust, we would suggest gently blowing pressurized air onto the surface of the detector, from a ~6" distance. If further cleaning is needed, you can use ethyl alcohol an wipe off the dirt carefully. It is not recommended to use organic solvents, as they can degrade the quality of any resin coating or filters.
Posted Date:2010-11-03 17:42:40.0
I have a bunch of Thorlabs Si-photodiodes, biased and amplified. What is the procedure for the sensing area cleaning in the case if gets dirty or dusty ? Unlike conventional photodiodes, these detectors are not in some protective case with transparent window. Do they really have any protective layer on the Si ?
Posted Date:2009-09-06 17:47:28.0
A reply from Jens at Thorlabs: as for the maximum power we do not recommend to use more than 100mW over the detector area. You will find higher values in some publications, depending on wavelenght and exposure time and this value is more on the safe side. As to the inhomogenity the laser point located at different spots on the detector surface does indeed not produce the same conversion because of boundary conditions. These boundary conditions vary from diode to diode. To get a true estimate we can map out the area of the photo diode. I will contact you with additional data regarding the measurement. If possible the 2/3 rule (i.e. filling 2/3 of the detector aperture) should be followed.
Posted Date:2009-08-31 12:38:28.0
Hi, I am currently using a PDA100A but it seems that the sensitivity to the impinging laser light is not the same on all area of the photon detector. We have almost 10% of difference between different area. It might be possible that our PDA100A had been damaged by being exposed to a high power laser beam. But before buying a new one, could you please provide me some information about the accuracy of this photon detector (I mean the difference of sensitivity between the different cells of the detector) and about the maximum power that we can use without damaging the detector.
Posted Date:2009-08-03 17:36:13.0
A response from Ken at Thorlabs to asd: All the US and EC versions had different power supplies originally and the EC (220-240VAC) power supplies were more expensive. We did not change to the current new switchable power supply until about a year ago. We will be updating the prices shortly.
Posted Date:2009-08-02 18:11:34.0
How come the the PDA3A-EC is so much more expensive than the PDA36A? The other detectors dont show this skew in price and the PSUs are identical. Looks like a consumer annoying cock up.
Posted Date:2009-07-09 10:00:13.0
A response from Ken at Thorlabs to perry.gray: We do carry SM1 to C-mount adapters. SM1A10 has external SM1 Threads and internal C-Mount Threads while SM1A9 has internal SM1 Threads and external C-Mount Threads.
Posted Date:2009-07-08 21:35:37.0
You guys need a C-mount adapter for your PDA series diodes so I can mount my existing c-mount tv camera lenses on my PDA diode housings
Posted Date:2009-06-09 13:16:54.0
A response from Adam at Thorlabs to Letizia: Hi, We do not have data on the thermal drifts for these units. If you provide me with the temperature ranges you may be using the PDA25k at , I can check with our electronics engineers and see if we can provide more inforamtion. My email address is
Posted Date:2009-06-09 11:42:19.0
Response from Adam at Thorlabs, Inc. Hi, I have spoken with our electronics engineers and there should be no need to distance the power supply from the photodiode. I am also checking with our engineers to see if we can provide any data about the shot noise. As soon as I have more information, I will send you an email. If you have further questions or concerns, feel free to contact me,
Posted Date:2009-06-09 11:28:37.0
Hello, I need to know if there is any requirement concerning the distance from the power supply to the photodiode. I have just seen a comment saying that "the power supply needs to be located about 5 meters away". Could you tell me more about that? I also need some data concerning the shot noise. Can the phase of the signal be deteriorated by the photodiode? In fact, we need to extract the phase from the output signal and we need a very high precision on the signal phase. If you do have any data, please let me know. Thanks in advance. Best regards
Posted Date:2009-04-15 03:47:47.0
could you please specify the temperature coefficient (thermal drift) for PDA25k? thank you ldm
Posted Date:2009-01-22 11:00:47.0
Response from Laurie at Thorlabs to lee: Thank you for your interest in Thorlabs Products. A member of our technical support staff will be contacting you directly. We need a bit of clarification concerning your inquiry prior to discussing possible solutions.
Posted Date:2009-01-20 04:13:57.0
I plan to use PDA10A in an equipment, but the power supply needs to be located about 5 meters away. Ill be using a linear +/-12V power supply on DIN rail. I prefer to make the power supply cable in house, and so Id appreciate it if (1) Thorlabs sells the cable-side power connector (not the whole cable like PDA-C-72), or (2) gives relevant information such as connector manufacturer and part number.
Posted Date:2008-12-10 13:37:22.0
Response from Laurie at Thorlabs to jwerly: Thank you for your feedback concerning our PDA photodetectors. The transimpedance photocurrent amplifier assembly is built directly into the circuitry of the PDA detector, and thus, it is not possible to control the amplification externally or through some other method. Detectors like the PDA36A have switchable gain, but again, there is no way to adjust the amplification.
Posted Date:2008-12-09 09:11:15.0
Hello, I have a question about your PDA series. I would know how can we control the amplification. I mean, is it an automiticaly, a manualy or even a manualy by an electronic interface ? Regards, Julien Werly.
Posted Date:2008-03-06 09:55:47.0
Response from Sal at Thorlabs to jschumacher, ghegenbart, and acable: Numerous changes have been made to this page to address the postings below. The PDA8GS is a high-speed, fiber coupled detector that is now included with the other detectors in that family. The FPD310 high speed PIN photodiode module is accessible directly from its own window in the Biased and Amplified Detector Visual Navigation pane. Regarding this page, the pin description for the PDA Power Connector is in a diagram immediately next to the price and description of this component. All detectors are now grouped by material type (InGaAs and Ge are separated). The New vs. Old tab includes explicit references between current and superseded devices and the superseded devices are hot links that will lead to their documentation. This arrangement insures easy access to the old part information. The Overview tab has been completely reorganized to present the modules grouped both by high level feature (Switchable Gain, Wideband, etc.), application, and detector type (Si, InGaAs, etc.). The Specs tab also has been grouped by detector type. Gain figures are easy to read and units are expressed in both V/A and ohms since both units are generally used. Finally, under the Graphs tab a complete set of spectral responsivity data is included for each model number. We continually strive to assist our customers in finding the product that is best suited to their application. Thanks for your continued business.
Posted Date:2007-12-27 16:44:57.0
In response to ghegenbarts comments, we have split the InGaAs and Ge subgroups as was done with the DETs page. We have also updated the product descriptions to be more uniform. Please note that acables comments are still being addressed by the technical marketing group. We thank you for your input, and hope that you find these changes to be helpful.
Posted Date:2007-12-12 05:55:15.0
Your "Specs" tab would be much easier to read if it was separated by detector type, when using the chart i am forced to piece together what Si detectors are available, it is great to have a large selection of products but as you expand the selection please realize that more thought should go into how you organize the presentation. I would also suggest a selection table right on the Overview tab, all the text is great for the first time visitor, added the table would just complete the overview picture faster for your more experienced customers. Another point that is confusing for me as a repeat customer is the non-uniformity of the product descriptions in the price boxes. Since i know the detector family fairly well and just need to pick out the right model it would be great to have all the relevant information right in your price table, there seems to be room. For me the order of importance is: What it Is: Handled with your Price Box Header Material: (which you handle well by separating the boxes by material) Bandwdith: (highest if switchable gain but provide foot note) Gain: (number if fixed and range if variable) Wavelength Range: (given by material in most cases) Ex: PDA10A, 150MHz BW, 5KOhm Gain, 200-1100nm Detector Also, my sense is that the transimpedence gain in units of Ohms is the standard way to specifiy an amplified detector, why the V/A, silly little thing but it caused me to have to pause.
Posted Date:2007-12-12 05:27:23.0
I came to this page specifically to cross reference an old PDA part number to a new one and was disapointed to find that this information was not provided on the "New vs Old Design" tab. Can you add a simple chart and then ensure the internal search feature can "see" the old part numbers. Does your search feature even have the ability to send a visitor to a specific tab.
Posted Date:2007-11-26 08:14:26.0
I suggest not to combine InGaAs and Ge in one product group but have them listed separately like it is done for the DETs.
Posted Date:2007-10-18 12:58:43.0
please add pin description for PDA power connector

InGaAs Transimpedence Amplified Photodetectors

Click Images to Enlargea PDA20C PDA10CF PDA20Cs PDA10CS PDA10D
Detector Element
(Click for Image)
InGaAs InGaAs InGaAs InGaAs InGaAs
Wavelength Range 800 - 1700 nm 800 - 1700 nm 800 - 1700 nm 900 - 1700 nm 1200 - 2600 nm
Responsivity Curve More Info More Info More Info More Info More Info
Active Area 3.14 mm2
(Ø2.0 mm)
0.2 mm2
(Ø0.5 mm)
3.14 mm2
(Ø2.0 mm)
0.8 mm2
(Ø1.0 mm)
0.8 mm2
(Ø1.0 mm)
Gain Fixed: 500 kV/A / 175 kV/Ab Fixed: 10 kV/A / 5 kV/Ab 8 x 10 dB Steps 8 x 10 dB Steps Fixed: 10 kV/A / 5 kV/Ab
Bandwidth Range DC - 5 MHz DC - 150 MHz DC - 10 MHz DC - 17 MHz DC - 15 MHz
Noise Equivalent Power (NEP) 22x10-12 W/Hz1/2 1.2x10-11 W/Hz1/2 1.14x10-12 - 5.12x10-11 W/Hz1/2 1.25x10-12 - 6.0x10-11 W/Hz1/2 3.5x10-11 W/Hz1/2
  • All photodetectors are shown with the included SM1T1 Internal SM1 Adapter attached.
  • Gain Values at Hi-Z / 50 Ω Loads
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Imperial Price Available / Ships
PDA20C Support Documentation
PDA20CCustomer Inspired!InGaAs Fixed Gain Detector, 800-1700 nm, 5 MHz BW, 3.14 mm2, 120 VAC
PDA10CF Support Documentation
PDA10CFInGaAs Fixed Gain Detector, 800-1700 nm, 150 MHz BW, 0.2 mm2, 120 VAC
PDA20CS Support Documentation
PDA20CSInGaAs Switchable Gain Detector, 800-1700 nm, 10 MHz BW, 3.14 mm2, 120 VAC
PDA10CS Support Documentation
PDA10CSInGaAs Switchable Gain Detector, 900-1700 nm, 17 MHz BW, 0.8 mm2, 120 VAC
PDA10D Support Documentation
PDA10DInGaAs Fixed Gain Detector, 1.2-2.6 µm, 15 MHz BW, 0.8 mm2, 120 VAC
+1 Qty Docs Part Number - Metric Price Available / Ships
PDA20C/M Support Documentation
PDA20C/MCustomer Inspired!InGaAs Fixed Gain Detector, 800-1700 nm, 5 MHz BW, 3.14 mm2, 230 VAC
PDA10CF-EC Support Documentation
PDA10CF-ECInGaAs Fixed Gain Detector, 800-1700 nm, 150 MHz BW, 0.2 mm2, 230 VAC
PDA20CS-EC Support Documentation
PDA20CS-ECInGaAs Switchable Gain Detector, 800-1700 nm, 10 MHz BW, 3.14 mm2, 230 VAC
PDA10CS-EC Support Documentation
PDA10CS-ECInGaAs Switchable Gain Detector, 900-1700 nm, 17 MHz BW, 0.8 mm2, 230 VAC
PDA10D-EC Support Documentation
PDA10D-ECInGaAs Fixed Gain Detector, 1.2-2.6 µm, 15 MHz BW, 0.8 mm2, 230 VAC

InGaAs Transimpedence Amplified Photodetector, Femtowatt Sensitivity

Item # PDF10C
Click Image to Enlargea PDF10C
Detector Element
(Click for Image)
Wavelength Range 800 - 1700 nm
Responsivity Curve More Info
Active Area 0.2 mm2
(Ø0.5 mm)
Gain Fixed: 1 x 108 kV/A
Bandwidth Range DC - 25 Hz
Noise Equivalent Power
7.5x10-15 W/Hz1/2
  • The photodetector is shown with the included SM1T1 Internal SM1 Adapter attached.

Each PDF10C(/M) detector includes a TRE(/M) electrically isolated TR post adapter.

Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Imperial Price Available / Ships
PDF10C Support Documentation
PDF10CInGaAs Amplified Detector, 800-1700 nm, 25 Hz, 0.2 mm2, 100-120 VAC
+1 Qty Docs Part Number - Metric Price Available / Ships
PDF10C/M Support Documentation
PDF10C/MInGaAs Amplified Detector, 800-1700 nm, 25 Hz, 0.2 mm2, 220-240 VAC

PDA Power Supply Cable

Pinout for Cable

The PDA-C-72 is a power cord for the PDA line of amplified photodetectors. The cord has tinned leads on one end and a PDA-compatible 3-pin connector on the other end. It can be used to power the PDA series of amplified photodetectors with any power supply that provides a DC voltage. The pin descriptions are shown to the right.

Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available / Ships
PDA-C-72 Support Documentation
PDA-C-7272" PDA Power Supply Cable, 3-Pin Connector

12 VDC Regulated Power Supply

  • Replacement Power Supply for the Amplified Photodetectors Sold Above
  • ±12 VDC Power Output
  • Current Limit Enabling Short Circuit and Overload Protection
  • On/Off Switch with LED Indicator
  • Switchable AC Input Voltage (115 or 230 VAC)
  • 6.6 ft (2 m) Cable with LUMBERG RSMV3-657/2M Male Connector
  • UL and CE Compliant

The LDS1212 ±12 VDC Regulated Linear Power Supply is intended as a replacement for the supply that comes with our PDA line of amplified photodetectors sold on this page. The cord has three pins: one for ground, one for +12 V, and one for -12 V (see diagram above). This power supply ships with a location-specific power cord and the voltage switch is set to the proper setting for your location before it is shipped. This power supply can also be used with our PDB series of balanced photodetectors, our PMM series of photomultiplier modules, our APD series of avalanche photodetectors, and our dichroic atomic vapor spectroscopy systems.

Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available / Ships
LDS1212 Support Documentation
LDS1212±12 VDC Regulated Linear Power Supply, 6 W, 115/230 VAC

Internally SM1-Threaded Fiber Adapters

These internally SM1-threaded (1.035"-40) adapters mate connectorized fiber to any of our externally SM1-threaded components, including our photodiode power sensors, our thermal power sensors, and our photodetectors. These adapters are compatible with the housing of the photodetectors on this page.

Item # S120-SMA S120-ST S120-SC S120-LC
Click Image to Enlarge S120-SMA S120-ST S120-SC S120-LC
Fiber Connector Typea SMA ST SC LC
Thread Internal SM1 (1.035"-40)
  • Other Connector Types Available upon Request
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available / Ships
S120-SMA Support Documentation
S120-SMASMA Fiber Adapter Cap with Internal SM1 (1.035"-40) Thread
S120-ST Support Documentation
S120-STST/PC Fiber Adapter Cap with Internal SM1 (1.035"-40) Thread
S120-SC Support Documentation
S120-SCSC/PC Fiber Adapter Cap with Internal SM1 (1.035"-40) Thread
S120-LC Support Documentation
S120-LCLC/PC Fiber Adapter Cap with Internal SM1 (1.035"-40) Thread

Externally SM1-Threaded Fiber Adapters

Each disk has four dimples, two in the front surface and two in the back surface, that allow it to be tightened from either side with the SPW909 or SPW801 spanner wrench. The dimples do not go all the way through the disk so that the adapters can be used in light-tight applications when paired with SM1 lens tubes. Once the adapter is at the desired position, use an SM1RR retaining ring to secure it in place.

Adapter Image
(Click the Image to Enlarge)
Connector Type FC/PC FC/APC SMA ST/PC
Threading External SM1 (1.035"-40)
  • Please note that the SM1FCA has a mechanical angle of only 4°, even though the standard angle for these connectors is 8°. There is a 4° angle of deflection caused by the glass-air interface; when combined with the 4° mechanical angle, the output beam is aligned perpendicular to the adapter face.
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available / Ships
SM1FC Support Documentation
SM1FCFC/PC Fiber Adapter Plate with External SM1 (1.035"-40) Thread
SM1FCA Support Documentation
SM1FCAFC/APC Fiber Adapter Plate with External SM1 (1.035"-40) Thread
Lead Time
SM1SMA Support Documentation
SM1SMASMA Fiber Adapter Plate with External SM1 (1.035"-40) Thread
SM1ST Support Documentation
SM1STST/PC Fiber Adapter Plate with External SM1 (1.035"-40) Thread
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