International audienceAn analytical model based on Volterra nonlinear functionals applied to semiconductor lasers has been developed. Analytical expressions are obtained for different laser diode responses, giving powerful tools for analysis. For harmonic input, the response is given including the gain compression factor ε. Second-harmonic distortion (2HD) shows two maxima at half relaxation oscillation frequency ΩR/2 and at ΩR, in agreement with experiments; the residual dc component due to nonlinearities is estimated and experimentally verified. Dynamic frequency deviation as function of bias current shows resonant characteristics. Relaxation frequency and damping rate ΓR reveal their precise dependence on ε and differential gain A. For step input, the turn-on delay ton and the overshoot PP/Pon expressions of our model are only functions of ΓR and ΩR. PP/Pon, and the ringing phenomena decrease with increasing bias current leve
International audiencePrecision optical spectral lineshape measurements on semiconductor lasers using Michelson and Fabry-Perot interferometers are presented. Measurements ranging from 30 MHz up to 100 GHz give the spectral behavior above and below threshold even for very small emitted optical powers. Variations of the linewidth above and below threshold as a function of injected current are measured and used to evaluate the linewidth enhancement factor and behavior at threshold. The lineshape can differ from the modified Schawlow-Townes almost Lorentzian form for semiconductor lasers above threshold when submitted to operating system conditions such as modulation and optical feedback. Under modulation, line frequency and signal form are modified because of chirping effects. A simple method for chirp evaluation at low frequencies based on lineshape evaluation is proposed. Optical feedback effects are studied as a function of the feedback coefficient C showing various regimes differing for single-mode and multimode laser diode
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