Question

Will a deterministic gain introduce new noise? What about a random gain? Explain this in photoncurrent case.

Answer 1

the photocurrent is produced by photodiodes.ther are the number of photodiodes are available in the market. example of a photodiode is inear mode avalanche photo-diode. The optoelectronic gain of a linear mode avalanche photo-diode (APD) results from the cascade of electron and hole impact ionization that take place in the high-field intrinsic multiplication layer of the APD. Due to the uncertainty associated with the stochastic nature of the APD's gain, the shot noise present in the resulting photo-generated electrical signal is accentuated and degrades the detection of single photon initiated avalanche signals. Recent advances in linear mode InGaAs APD detectors have been demonstrated that have reduced excess noise, along with the high gain necessary for detecting single photons. In these devices, the avalanche buildup is characterized by a temporally varying noise. At low incident photon / photo-electron levels, the stochastic nature of the impulse response function of these APDs offers the potential of the increased probability that the output exceeds a threshold level resulting in a "detection" and, hence, a better receiver-operating-characteristic (ROC). In this paper, we examine the ROC (P detection vs P_FalseAlarm) statistics of these single-photon APDs as a function of the quasi-deterministic mean gain and standard deviation for an arms ROIC (readout integrated circuit) noise level is very less.