The Determination of Unity Gain for InGaAs/InP Avalanche Photodiodes With Excess Noise Measurements

We propose a methodology for determining the unity gain of avalanche photodiodes (APDs) with excess noise measurements. Compared with previous reports, the relative intensity noise from the laser can be deduced in our experiments, which alleviates the strict requirements for the light source during measurements. The unity gain of APDs can be determined from the abrupt change in the derivative function of the total noise versus the photocurrent. With the proposed technique, a relative error for gain is of 3.3%. Thus the excess noise can be extracted from the total noise and the keff can be derived with a satisfactory accuracy.