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Si Free-Space Amplified Photodetectors![]()
PDA36A2 Switchable Gain
Application Idea PDA Series Detector with Ø1" Lens Tube Attached to a 30 mm Cage System PDA10A2 Fixed Gain FPD610-FS-VIS Fixed Gain ![]() Please Wait
Features
We offer a selection of Silicon (Si) Free-Space Amplified Photodetectors that are sensitive to light in the UV to the NIR wavelength range. Thorlabs' amplified photodetectors feature a built-in low-noise transimpedance amplifier (TIA) or a low-noise TIA followed by a voltage amplifier. Menlo Systems' FPD series amplified photodetectors have a built-in radio frequency (RF) or transimpedance amplifier. We offer fixed-gain versions that possess a fixed maximum bandwidth and total transimpedance gain, as well as switchable-gain versions with two or eight gain settings. Thorlabs' photodetectors are designed to meet a range of requirements, with offerings that include the 380 MHz PDA015A fixed-gain detector with an impulse response of 1 ns, the high-sensitivity PDF10A2 detector with a minimum noise equivalent power (NEP) of 3.0 fW/Hz1/2, and the switchable-gain PDA100A2 device with eight switchable maximum gain (bandwidth) combinations from 1.51 kV/A (11 MHz) to 4.75 MV/A (3 kHz). The PDF10A2 with femtowatt sensitivity is a low-frequency device that should only be terminated into high impedance (Hi-Z) loads, while all other of our silicon amplified photodetectors are capable of driving loads from 50 Ω to Hi-Z. ![]() Click to Enlarge The PDA10A2 with the Included ±12 V Power Supply. Replacement power supplies are sold below. Every detector has internal SM05 (0.535"-40) threading and external SM1 (1.035"-40) threading. Except for some select detectors, each unit's housing features 8-32 tapped holes (M4 for -EC and /M models). The PDA10A2, PDA8A2, PDA36A2, PDA100A2, and PDF10A2 detectors feature a new housing with universal taps that accept both 8-32 and M4. For more information about the location of these mounting points and mounting these units, please see the Housing Features and Mounting Options tabs. Menlo Systems' FPD series detectors are easy-to-use photodiode packages with an integrated high-gain, low-noise RF (FPD310-FS-VIS) or transimpedance (FPD510-FS-VIS and FPD610-FS-VIS) amplifier. The FPD310-FS-VIS detector is ideal for experiments requiring high bandwidths and extremely short rise times (<1 ns). This detector has a switchable gain with two steps, 0 and 20 dB. The FPD510-FS-VIS and FPD610-FS-VIS fixed-gain detectors are optimized for the highest signal-to-noise ratio when detecting low-level optical beat signals at frequencies up to 250 MHz and 600 MHz, respectively. The FPD510-FS-VIS detector has a rise time of 2 ns, while the FPD610-FS-VIS device has a 1 ns rise time. The 3 dB bandwidth of these DC-coupled devices is 200 MHz for the FPD510-FS-VIS and 500 MHz for the FPD610-FS-VIS. The compact design of the FPD detectors allows for easy OEM integration. The housing of each Menlo detector features one M4 tapped hole for post mounting. For more information about the housing, please see the Housing Features tab. For versions of these detectors with FC/PC inputs, see Si Fiber-Coupled Amplified Detectors. ![]() Click to Enlarge Menlo Systems’ Detectors Include a Location-Specific ±12 V Power Supply Power Supply Menlo's FPD510-FS-VIS, FPD610-FS-VIS, and FPD310-FS-VIS detectors include a low-noise power supply. Performance Specifications
Gain SpecificationsFixed Gain Detectors
Switchable Gain Detectors
![]() Click to Enlarge Top of the housing on our PDA and PDF detector housings. The Power In connector, Output BNC connector, and power indicator LED are located at the top of the housing. The PDA015A detector is shown. ![]() Click to Enlarge The housings of Thorlabs' detectors feature internal SM05 and external SM1 threads. An SM1T1 SM1 Adapter with internal threads is included with each amplified photodetector, and an SM1RR Retaining Ring is included with the PDA015A, PDA10A2, PDA36A2, PDA100A2, and PDF10A2. Housing Features of the Amplified Si PhotodetectorsPlease refer to the table below for detailed drawings of each detector. PDA and PDF Detectors Lens Tube Compatibility Cage System Compatibility Post Mounting ![]() Click to Enlarge PDA Photodetector Mounted Horizontally ![]() Click to Enlarge PDA Photodetector Connected to an SM1 Lens Tube in a 30 mm Cage System ![]() Click to Enlarge PDA Photodetector Integrated into a 30 mm Cage System Using the External SM1 Threads ![]() Click to Enlarge PDA Photodetector Integrated into a 30 mm Cage System Using the SM1T1 (included) and SM1T2 Adapter
PDA and PDF Series DetectorsBNC Female Output (Photodetector)PDA10A2, PDA8A2, PDF10A2, PDA015A, PDA100A2, PDA36A2: 0 - 10 V Output Male (Power Cables)![]() Female Power IN (Photodetector)FPD Series DetectorsSignal Out- SMA Female (Photodetector)For connection to a suitable monitoring device, e.g. oscilloscope or RF-spectrum-analyzer, with 50 Ω impedance. Female (Power Cables)Male Power IN (Photodetector)![]() Photodiode TutorialTheory of OperationA 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.
Photodiode TerminologyResponsivity Modes of Operation (Photoconductive vs. Photovoltaic) Photoconductive Photovoltaic Dark Current 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.
Junction Capacitance Bandwidth and Response Noise Equivalent Power 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 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 Series Resistance Common Operating Circuits
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.
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. Effects of Chopping FrequencyThe 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 The following table lists Thorlab's selection of previous and current generation PDA, PDF, and DET detectors.
Pulsed Laser Emission: Power and Energy CalculationsDetermining 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.
![]() Click to Enlarge 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.
Example Calculation: 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.
The following table lists Thorlabs' selection of photodiodes and photoconductive detectors. Item numbers in the same row contain the same detector element.
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![]() ![]() 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. ![]()
Note: The APC adapters have two dimples in the front surface that allow them 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. FC/PC and FC/APC adapters are available with either narrow (2.0 mm) or wide (2.2 mm) key connectors; for more details on narrow versus wide key connectors, please see our Intro to Fiber tutorial. ![]()
Note: 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. FC/PC and FC/APC adapters are available with either narrow (2.0 mm) or wide (2.2 mm) key connectors; for more details on narrow versus wide key connectors, please see our Intro to Fiber tutorial. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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