Numerical investigation into the injection-locking phenomena of gain switched lasers for optical frequency comb generation

TL;DR

This paper uses numerical simulations to explore how injection-locking can generate optical frequency combs from gain-switched lasers, revealing a broader locking range and improved comb quality compared to continuous wave lasers.

Contribution

It demonstrates the dynamics of injection-locking in gain-switched lasers and shows how it enhances frequency comb generation with a larger locking range and better spectral properties.

Findings

Injection-locking range is larger for gain-switched lasers.

Optical frequency combs evolve from free-running to locked states.

FM-noise spectral density improves under injection-locking.

Abstract

We present detailed numerical simulations of the laser dynamics that describe optical frequency comb formation by injection-locking a gain-switched laser. The typical rate equations for semiconductor lasers including stochastic carrier recombination and spontaneous emission suffice to show the injection-locking behavior of gain switched lasers, and we show how the optical frequency comb evolves starting from the free-running state, right through the final injection- locked state. Unlike the locking of continuous wave lasers, we show that the locking range for gain switched lasers is considerably greater because injection locking can be achieved by injecting at frequencies close to one of the comb lines. The quality of the comb lines are formally assessed by calculating the FM-noise spectral density and we show that under injection-locking conditions the FM-noise spectral density of the comb lines tend to that of the maser laser.