Autocorrelation function and emission spectrum of single-transverse-mode heterolasers in the self-sustained intensity pulsation regime

The degree of time coherence of semiconductor lasers operating in the self-intensity pulsation regime is studied by two methods. In the first method measurements were performed with a Michelson interferometer by recording the autocorrelation function, while in the second (spectral) method the spectral density of emission was measured. It is shown that both methods give similar results; however, the spectral method can understate the degree of coherence by the value up to 30% due to a great contribution of spontaneous emission to a recorded signal.