Phase randomness in a gain-switched semiconductor laser: stochastic differential equation analysis

TL;DR

This paper provides a theoretical analysis of phase randomness in gain-switched semiconductor lasers, revealing how phase diffusion depends non-linearly on bias current and is influenced by gain saturation, impacting quantum random number generation.

Contribution

It introduces a stochastic differential equation model to analyze phase diffusion, highlighting the effects of gain saturation and high pulse rates on phase randomness in lasers.

Findings

Phase diffusion exhibits non-linear dependence on bias current.

Gain saturation significantly affects phase diffusion.

High pulse rates reduce phase diffusion efficiency.

Abstract

We performed theoretical analysis of the phase randomness in a gain-switched semiconductor laser in the context of its application as a quantum entropy source. Numerical simulations demonstrate that phase diffusion r.m.s. exhibits non-linear dependence on the bias current, which could be of significant practical importance, particularly, in application to high-speed optical quantum random number generators. It is shown that phase diffusion between laser pulses cannot always be assumed to exhibit required efficiency, particularly, at high pulse repetition rates. It was also revealed that the gain saturation significantly affects the r.m.s. value of the phase diffusion and, in essence, determines the degree of non-linearity of its dependence on the pump current.