Amplitude-phase decorrelation: a method for reducing intensity noise in semiconductor lasers

Abstract

It has been shown that the method of amplitude-phase decorrelation can reduce the fundamental intensity noise floor of semiconductor laser light over a wide bandwidth by the ratio 1/(1+α^2), where α is the linewidth enhancement factor. The method uses a dispersive element to convert phase noise into intensity noise. This technique was recently demonstrated by reducing intensity noise from a DFB (distributed feedback) laser as much as 7 dB below its intrinsic level. In the present work, the authors extend these results by characterizing the frequency dependence of the noise reduction. Optimum reduction is achieved in the flat region of the spectrum and diminishes at higher frequencies approaching the relaxation resonance. The correlation properties of the fluctuations are also investigated.