ABSTRACT
The birth of photodetectors can be dated back to 1873 when Smith discovered photoconductivity in selenium. There are two general types of photon detectors without internal gain: photoconductive and junction devices. The majority of optical detectors can be classified in two broad categories: photon detectors and thermal detectors. The practical operating limit for most IR detectors is the background fluctuation limit also known as the background limited infrared photodetector (BLIP) limit. A common problem of any type of photon detector is how to terminate the photodetector with a suitable load resistor and to trade off the performance between bandwidth and signal-to-noise ratio (SNR). A lock-in amplifier uses phase-sensitive detection to improve the SNR in continuous wave (cw) experiments. In energy spectroscopy, the integration of detector current pulses is performed using preamplifier based on charge-sensitive amplifier (CSA).
