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Free-Space InAsSb Amplified Detector
PDA07P2 with Ø1" Lens Tube Attached to a 30 mm Cage System
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The PDA07P2 has internal SM05 and external SM1 threads and includes an
SM1T1 Internal SM1 Adapter
and SM1RR Retaining Ring.
Click to Enlarge
The back plate of the PDA07P2 is engraved with the detector's responsivity curve at 25 °C ambient temperature.
The PDA07P2 is an InAsSb (indium arsenide antimonide)-based, transimpedance-amplified photodetector that is sensitive to light in the MIR spectral range, specifically from 2.7 µm to 5.3 µm. This fixed-gain detector features a 3 x 105 V/A high-impedance gain and is housed in a compact, low-profile package that is ideal for use in light paths with space constraints. The maximum output of the PDA07P2 is
Since this detector features a 50 Ω load at the output of the BNC connector, it can be used with Thorlabs' passive high-pass filters, which have a low-impedance input of 50 Ω and a high-impedance output that allows them to be directly attached to high-impedance measurement devices such as an oscilloscope. Thus, only use the high-pass filter and detector with oscilloscopes with a high impedance input. Many high-speed oscilloscopes have input impedances of 50 Ω, so we do not recommend installing a 50 Ω terminator. The combined loads will equal 25 Ω, which could allow ~135 mA of output current, damaging the output driver of the PDA07P2.
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PDA07P2 Shown with Included Power Supply
The housing of the PDA07P2 features external SM1 (1.035"-40) threading, internal SM05 (0.535"-40) threading, and two universal mounting holes that accept both 8-32 and M4 threads, allowing for either vertical or horizontal post mounting. Addtionally, an SM1T1 internally threaded SM1 coupler and SM1RR retaining ring are included, allowing convenient mounting of SM1-compatible accessories, optics, and cage assembly accessories. 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. 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). Most SM1-threaded fiber adapters are compatible with this detector. However, the S120-FC internally SM1-threaded fiber adapter is not compatible because it collides with the photodiode. Externally SM1-threaded adapters should be mated to the included internally SM1-threaded adapter, while internally SM1-threaded adapters can be mated directly to the housing. See below for our selection of SM1 thread adapters.
The active area of the photodetector is flush with the front of the housing, simplifying alignments within optomechanical systems. Inhomogeneities at the edges of the active area of the photodetector can generate unwanted capacitance and resistance effects that distort the time-domain response of the photodetector output. Therefore, Thorlabs recommends centering the incident light onto the photodetector's active area. For a detailed drawing of the detector, please see the diagram under the Housing Features column below. We do not recommend exceeding a power density of 1 W/cm2 for light incident on the detector's active area.
InAsSb Detector with TEC
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The power input and DC-coupled BNC connector are located at the top of the housing.
Click to Enlarge
The detector has internal SM05 and external SM1 threads and includes an
SM1T1 Internal SM1 Adapter
and SM1RR Retaining Ring.
PDA Series Housing Features
Thorlabs' PDA07P2 is a compact InAsSb amplified photodetector with a fixed gain. This detector's housing features internal SM05 (0.535"-40) threading and external SM1 (1.035"-40) threading. It includes an SM1T1 internally SM1-threaded adapter and SM1RR retaining ring. Most SM1-threaded fiber adapters are compatible with this detector.
Threaded holes on the housing allow the unit to be mounted in a horizontal or vertical orientation, which gives the user the option to route the power and BNC cables from above or alongside the beam path. The PDA07P2 housing features the active area flush with the front of the housing, simplifying alignments within optomechanical systems. This design also has two universal-threaded holes compatible with both 8-32 and M4 threads (see the table below). As a convenience, the back panel is engraved with the responsivity curve of the photodiode. For more information on mounting these units, please see the Mounting Options tab.
PDA and PDF 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.
TR Series Post (Ø1/2" Posts) System
The PDA housing can be mounted vertically or horizontally on a TR Series Post using the threaded holes for 8-32 (M4 on metric versions). Select PDA housings feature universally threaded holes for both 8-32 and M4 threads.
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.
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 and use the external SM1 threads. A cage plate, such as the CP02 30 mm cage plate, can be directly attached to the SM1 threads. Then the retaining ring, included with the SM1T1, can be threaded using a spanner wrench into the CP02 to ensure the cage plate is tightened to the desired location and square with the photodetector housing.
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, an 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.
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.
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.
BNC Female Output, DC Coupled
|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 (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):
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:
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.
A load resistance is used to convert the generated photocurrent into a voltage (VOUT) for viewing on an oscilloscope:
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 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 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.
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.
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:
where GBP is the amplifier gain bandwidth product and CD is the sum of the junction capacitance and amplifier capacitance.
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
Determining whether emission from a pulsed laser is compatible with a device or application can require referencing parameters that are not supplied by the laser's manufacturer. When this is the case, the necessary parameters can typically be calculated from the available information. Calculating peak pulse power, average power, pulse energy, and related parameters can be necessary to achieve desired outcomes including:
Pulsed laser radiation parameters are illustrated in Figure 1 and described in the table. For quick reference, a list of equations are provided below. The document available for download provides this information, as well as an introduction to pulsed laser emission, an overview of relationships among the different parameters, and guidance for applying the calculations.
Peak power and average power calculated from each other:
|Peak power calculated from average power and duty cycle*:|
|*Duty cycle () is the fraction of time during which there is laser pulse emission.|
Figure 1: Parameters used to describe pulsed laser emission are indicated in the plot (above) and described in the table (below). Pulse energy (E) is the shaded area under the pulse curve. Pulse energy is, equivalently, the area of the diagonally hashed region.
|Pulse Energy||E||Joules [J]||A measure of one pulse's total emission, which is the only light emitted by the laser over the entire period. The pulse energy equals the shaded area, which is equivalent to the area covered by diagonal hash marks.|
|Period||Δt||Seconds [s]||The amount of time between the start of one pulse and the start of the next.|
|Average Power||Pavg||Watts [W]||The height on the optical power axis, if the energy emitted by the pulse were uniformly spread over the entire period.|
|Instantaneous Power||P||Watts [W]||The optical power at a single, specific point in time.|
|Peak Power||Ppeak||Watts [W]||The maximum instantaneous optical power output by the laser.|
|Pulse Width||Seconds [s]||A measure of the time between the beginning and end of the pulse, typically based on the full width half maximum (FWHM) of the pulse shape. Also called pulse duration.|
|Repetition Rate||frep||Hertz [Hz]||The frequency with which pulses are emitted. Equal to the reciprocal of the period.|
Is it safe to use a detector with a specified maximum peak optical input power of 75 mW to measure the following pulsed laser emission?
The energy per pulse:
seems low, but the peak pulse power is:
It is not safe to use the detector to measure this pulsed laser emission, since the peak power of the pulses is >5 orders of magnitude higher than the detector's maximum peak optical input power.
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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|
|150 - 550 nm||GaP||FGAP71||-||SM05PD7A||DET25K2||PDA25K2|
|200 - 1100 nm||Si||FDS010||-||SM05PD2A
|320 - 1100 nm||Si||-||-||-||-||PDA8A2|
|340 - 1100 nm||Si||FDS10X10||-||-||-||-|
|350 - 1100 nm||Si||FDS100
|400 - 1000 nm||Si||-||-||-||-||PDA015A(/M)
|400 - 1100 nm||Si||FDS015 b||-||-||-||-|
|400 - 1700 nm||Si & InGaAs||DSD2||-||-||-||-|
|500 - 1700 nm||InGaAs||-||-||-||DET10N2||-|
|750 - 1650 nm||InGaAs||-||-||-||-||PDA8GS|
|800 - 1700 nm||InGaAs||FGA015||-||-||-||PDA015C(/M)|
|800 - 1800 nm||Ge||FDG03
|900 - 1700 nm||InGaAs||FGA10||-||SM05PD4A||DET10C2||PDA10CS2|
|900 - 2600 nm||InGaAs||FD05D||-||-||DET05D2||-|
|950 - 1650 nm||InGaAs||-||-||-||-||FPD310-FC-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
|2.0 - 10.6 µm||HgCdTe (MCT)||VML10T0
|2.7 - 5.0 µm||HgCdTe (MCT)||VL5T0||-||-||-||PDAVJ5|
|2.7 - 5.3 µm||InAsSb||-||-||-||-||PDA07P2|
|Item #a||Housing Featuresb||Active Areac,d||Wavelength
|Noise-Equivalent Power (NEP)||Load
|Transimpedance Gain||Noise (RMS)||Responsivity
||2.7 - 5.3 µm||9 MHz||50 Ω to Hi-Z||1.5 x 105 V/A (50 Ω)
3 x 105 V/A (Hi-Z)
Click Here for
|10 to 50 °C||Yes|
The PDA-C-72 power cord is offered for the PDA line of amplified photodetectors when using with a power supply other than the one included with the detector. 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.
The LDS12B ±12 VDC Regulated Linear Power Supply is intended as a replacement for the supply that comes with our PDA and PDF 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). A region-specific power cord is shipped with the LDS12B power supply based on your location. This power supply can also be used with the PDB series of balanced photodetectors, PMM series of photomultiplier modules,APD series of avalanche photodetectors, and the FSAC autocorrelator for femtosecond lasers.
These internally SM1-threaded (1.035"-40) adapters mate terminated 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.
The APC adapter has two dimples in the front surface that allow it to be tightened with the SPW909 or SPW801 spanner wrench. The dimples do not go all the way through the disk so that the adapter can be used in light-tight applications when paired with SM1 lens tubes.
(Click the Image
|Fiber Connector Type||FC/APCb||SMA||ST/PC||SC/PCc||LC/PC|
|Thread||Internal SM1 (1.035"-40)|
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.
(Click the Image to Enlarge)
|Threading||External SM1 (1.035"-40)|