閾値電流付近でバイアス印加された単一モード半導体レーザーの光位相統計量の測定

We report on the experimental analysis of the statistics of the optical phase of the light emitted by a distributed-feedback (DFB) laser. We measure the dependence of the phase diffusion coefficient on the applied bias current in the region around the threshold current. We measure the phase noise statistics using three different methods based on i) averages of the noise phase trajectories over different temporal windows, ii) the variance of the phase noise difference, and iii) the frequency noise spectral density. The comparison between the results obtained with these methods is succesful. We obtain that the phase diffusion coefficient monotonously decreases with the bias current in the region around threshold. We finally compare our experimental results with simple analytical expressions for the below and above threshold cases based on Schawlow-Townes laws.