Numerical simulation of phase noise in hybrid square-rectangular lasers

A numerical scheme for calculating phase noise is proposed for hybrid square-rectangular semiconductor lasers. By establishing a two-section single-mode rate equation model driven by Langevin noise sources and considering the nonlinear gain effect, we numerically studied the phase noise characteristics and linewidth of the hybrid-cavity laser. The time-varying spectra of carrier density, photon density and phase are simulated and the frequency spectra of phase noise are presented with the help of the fast Fourier transform. With the increase of the bias current, the frequency noise has an obvious downward trend and a narrower linewidth is obtained. The linewidth of the hybrid square-rectangular laser is calculated according to the phase noise at low frequency. The simulated linewidth of the hybrid-cavity semiconductor laser is 0.36 MHz at the linewidth enhancement factor of 3 when the square microcavity bias current is 20 mA and the FP cavity bias current is 100 mA.