Photovoltaic detectors time response

Photovoltaic MCTIR detectors with response times on the order of five nanoseconds are now available. 

A common additional requirement on a detector is to minimize its response time. The response time of a photovoltaic detector is often determined by its RC time constant [4.7]. Thus for a given RA, one wants to minimize the capacitance per unit area of the junction. 

The speed of response of a photovoltaic detector is often determined by its RC time constant, as noted in Subsection 4.2.1. TheRC time constant is given by the product of RA and (4.30) taking this product and substituting (4.39) for W we get... 

MCT detectors may be operated in the photoconductive (PC) or photovoltaic (PV) mode, with PC operation being the more common. PV-MCT detectors are used when the response time of the measurement must be very short. Because the D of most PC-MCT detectors is approximately constant between modulation frequencies from 1 kHz to 1 MHz, it is difficult to drive the interferometer mirror... 

The time resolution is limited primarily by the response time of the detector. For measurements in the mid-infrared, the response time of a conventional photocon-ductive MCT detector will limit the resolution to between 1 ps and 100 ns. When a photovoltaic MCT detector is used, the resolution improves by about a factor of 10, and a time resolution of 10 ns has been claimed for most measurements with this detector. 

Time resolution is limited by the response speed of the detector and amplifier, and the speed of taking signals into the AD converter. If the pulse width of the external stimulus is short enough at a time resolution of about 100 ns, an absorbance change of smaller than 10 " is detectable [1]. In measurements using a photovoltaic MCT detector capable of producing output in both AC and direct current (DC) and a high-speed preamplifier [1,9], a time resolution of about 10 ns has been achieved. 

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