400 MHz Photoreceiver HCA-S-400M


  • Si-PIN and InGaAs-PIN photodiodes
  • Wavelength range from 320 to 1700 nm
  • Bandwidth DC to 400 MHz
  • Rise time 1 ns
  • Max. conversion gain 4.8 x 103 V/W
  • Free space or fiber optic input
Photodiode0.8 mm Ø Si-PIN0.3 mm Ø InGaAs-PIN (FST model)
integrated ball lens (FC model)
Spectral Range 320 – 1000 nm900 – 1700 nm
Bandwidth (-3 dB)DC – 400 MHzDC – 400 MHz
Rise/Fall Time (10% – 90%) 1 ns1 ns
Transimpedance 5 x 103 V/A5 x 103 V/A
Max. Conversion Gain 2.7 x 10V/W (@ 800 nm)4.8 x 10V/W (@ 1550 nm)
Min NEP (@ 100 MHz) 40 pW/√Hz (@ 800 nm)24 pW/√Hz (@ 1550 nm)

Output voltage ±1.0 V (for linear operation @ 50 Ω load). Offset adjustable by potentiometer. Output short-circuit protected. Photoreceivers with free space input come with threaded M4 and 8-32 mounting holes for use with standard mounting posts. Power supply ±15 V via 3-pin Lemo® socket. A mating connector is provided with the device. Optional power supply PS-15 available. For further information please view the datasheet or contact FEMTO.

High sensitivity at high bandwidth

The series HCA-S-400M Photoreceivers combine fast photodiodes with the proven and outstanding FEMTO HCA current amplifier technology. The HCA-S-400M is available with either a fast Silicon or InGaAs photodiode covering a spectral range from 320 to 1000 nm and 900 to 1700 nm, respectively. The amplifier transimpedance is 5 x 103 V/A resulting in a maximum conversion gain of 4.8 x 103 V/W at 1550 nm for the InGaAs model, and 2.7 x 103 V/W at 800 nm for the model with Silicon photodiode. The sophisticated DC coupled multistage amplifier design allows measurements from DC to a maximum bandwidth of 400 MHz corresponding to a minimum rise time of 1 ns. Due to the low noise design signals with an optical power in the micro Watt range can be detected without the need for further averaging. Different models with free space or fiber-optic input are available.

Compatible with optical bench (free space) and fiber optics

The free space input (FST) is designed as a 1.035″-40 threaded flange with a screw-on coupler ring. It opens up a broad compatibility with optical accessories from various manufacturers, such as lenses, tubes, cage systems, optical adapters etc.

The free-space input can be converted into fiber connections (FC, FSMA) easily by simply screwing on the fiber adapter of the PRA series.

The relatively large-area detector facilitates optical focusing in free-space applications and ensures a high and stable degree of coupling when using the optionally available fiber optic adapter. For models with detector areas smaller than Ø 0.4 mm, the use of fiber adapters is only recommended to a limited extent, since coupling losses and instabilities can occur. If the focus is on high-precision fiber optic measurements, using FC-models with fixed optical fiber input will usually give the best results.

All HCA-S photo receivers with free space input are equipped with UNC 8-32 and M4 threaded holes and can therefore be conveniently and stably integrated into optical systems on standard rod holders. The optionally available adapter plate PRA-PAP opens up further mounting options.


  • Spectroscopy
  • Fast pulse and transient measurements
  • Optical triggering
  • Test of digital fiber-optic systems
  • Optical front-end for oscilloscopes and A/D converters

Related products / accessories

Power Supply


Post Adapter Plate