Modification of power spectrum and frequency noise of a single-frequency semiconductor laser

Abstract

It is well established that the performance of a coherent optical fiber communication system depends critically on the frequency noise of the light source.1 We present in this paper study of the correlation between the laser linewidth or power spectra and their underlying contributor, frequency noise. In addition, utilizing the amplitude-to-frequency modulation conversion in semiconductor lasers, we showed the capability of altering the frequency noise and thus linewidth of a laser by the addition of amplitude noise. Our results are as follows: (1) The intrinsic power spectrum for the composite cavity laser is Lorentzian and the frequency noise is white. (2) On the addition of white amplitude noise to the laser, Lorentzian line shapes are retained while the linewidth is increased by a factor of 20. (3) With higher-noise power, the power spectra become asymmetric due to the excessive amplitude modulation induced by the variation of injection current.