Low Level Optical Feedback in Semiconductor Lasers as a Tool to Identify Nonlinear Enhancement of Device Noise

Recent studies of nonlinear dynamics in semiconductor-laser-with-optical- feedback (SLwOF) systems have discovered that very low levels of optical feedback enhance several, specific, narrow frequency bands within the broad bandwidth of the noise of the free running laser, in a systematic way as the injection current is increased [1]. Similar frequency features are also extracted when completing instantaneous frequency measurement (IFM) on the real-time output power data from semiconductor lasers operated at low injection current [2]. We report further investigation of the nonlinear behaviour of these noise peaks in a SLwOF system and their relevance as driving frequencies in the nonlinear dynamics of the SLwOF systems. The significance of this nonlinear noise measurement to device specification is also evaluated.