Intensity and phase noise of semiconductor lasers operating in single mode

Semiconductor lasers often involve various noise and instability problems due to fluctuation of photon and carrier numbers. In this paper, we analyze the quantum noise, both intensity and phase, of semiconductor lasers operating in single mode. Direct numerical integration of the self-consistent rate equations has been used to overcome limitations of the small-signal analysis. Langevin noise sources for photon number and phase have been used to count fluctuations due to spontaneous emission and the process of carrier recombination. Rate equations are applied to 850-nm GaAs lasers. Fast Fourier Transform (FFT) has been used to calculate the frequency spectra of both intensity and phase noise. Noise characteristics for different injection currents have been demonstrated. Results show that both intensity and phase noise decreases as the injection current density increases and the linewidths were decreasing substantially with increasing injection current as well.