Optical and Electronic Shot Noise: Signal to Noise Analysis

This lecture discusses the concepts of optical and electronic shot noise in the context of signal detection. The instructor begins by introducing a detector that transforms incoming optical power into an electrical current, emphasizing the importance of considering discretization noise, specifically shot noise, in both the optical and electronic domains. The lecture presents calculations for the signal-to-noise ratio (S/N) before and after detection, highlighting the differences in shot noise characteristics. The instructor explains how the optical signal's shot noise is calculated based on the input optical power and bandwidth, while the electronic shot noise is derived from the current output of the detector. A comparison of the S/N ratios reveals that a non-optimal quantum efficiency negatively impacts the overall detectivity, leading to an increase in noise equivalent power (NEP). The lecture concludes with a summary of the implications of quantum efficiency on noise and detectivity, reinforcing the relationship between these concepts in optical detection systems.