What does the amplification process in an avalanche photodiode (APD) introduce into the electrical output?

The amplification process in an avalanche photodiode (APD) significantly increases the gain of the electrical signal by creating additional charge carriers through impact ionization. While this process enhances the sensitivity of the device, it also introduces a certain level of noise into the electrical output. This noise results from the statistical nature of the multiplication process in the APD, where the generation of excess carriers can lead to fluctuations in the output signal. The noise introduced can limit the overall performance of the system, especially in low-light conditions.

Understanding how amplification in APDs operates helps in recognizing that while it provides higher signal levels, this signal is accompanied by an increase in noise, which can affect signal processing and overall system performance.