Characterization of White and Flicker Frequency Modulation Noise in Narrow-Linewidth Laser Diodes

Frequency modulation noise of narrow-linewidth external cavity laser diodes is characterized in terms of power spectral density (PSD) using the recirculating delayed self-heterodyne method. The measured PSD is consistent with the oscillator noise model consisting of white and flicker noise. Based on this model, beat signal spectra observed in heterodyne measurements are derived, which explain well the delay- or observation time-dependent lineshape obtained in the experiments.