FEMTO are pleased to introduce two new products: the HCA-S-20M-SI-FST and the HCA-S-20M-BSI-FST. These two models complete their portfolio of 20 MHz photoreceivers — a series launched a few months ago with the HCA-S-20M-IN-FST.
HCA-S-20M-SI-FST: 20 MHz Photoreceiver with Si-PIN Photodiode
The HCA-S-20M-SI-FST utilizes a standard Si PIN photodiode with an active area diameter of 3 mm. We recommend it for applications that benefit from a large photodiode. There is no direct equivalent from other manufacturers.
Key Features:
- Bandwidth DC up to 20 MHz
- Gain 1 x 10^5
- wavelength range 320 - 1060 nm
- active area 3 mm Ø
- NEP 4.5 pW/√Hz
Download datasheet here.
HCA-S-20M-BSI-FST: 20 MHz Photoreceiver with Black Silicon Photodiode
The HCA-S-20M-BSI-FST employs a "Black Silicon" photodiode with an active area of 1 x 1 mm² and offers excellent sensitivity in the 200 to 1100 nm range. We recommend the "Black Silicon" variant provided that the smaller photodiode size is not a limiting factor; in that case, it significantly outperforms the HCA-S-20M-SI-FST.
Key Features:
- Bandwidth DC up to 20 MHz
- Gain 1 x 10^5
- wavelength range 200 - 1100 nm
- active area 1 x 1 mm²
- NEP 3.3 pW/√Hz
Download data sheet here.
Image of HCA-S-20M-BSI-FST shown above at top of page.
A brief explanation of the technology behind "black silicon":
A black silicon photodiode is similar to a conventional silicon photodiode but features a surface modified with micro- and nanostructures that absorb almost all incident light. This gives the silicon surface a deep black appearance and minimizes reflection losses. While conventional polished silicon reflects up to 40% of incident light—depending on the wavelength—black silicon typically exhibits reflection levels below 1% across a broad spectral range. The result is exceptionally high quantum efficiency over a wide range of wavelengths (see https://www.femto.de/images/pdf-dokumente/de-hca-s-20m-bsi.pdf, page 4). In the 220 nm to 1010 nm wavelength range specifically, the quantum efficiency of the silicon surface approaches 100%; only the photodiode package's protective window limits the quantum efficiency to approximately 90%.
For further information, please contact