Frequency drift and instantaneous linewidth broadening of phase-section tuned SG-DBR laser

We experimentally investigate the spectral dynamics of a phase-section tuned sampled-grating distributed Bragg reflector (SG-DBR) laser by using optical heterodyne method. The measured time-resolved spectra of the beat signal illustrate that the beat signal suffers from both frequency drift and instantaneous spectrum broadening, which indicates that the wavelengths of the lightwaves experience drift and jitter. We study the variation of frequency drift and instantaneous linewidth broadening with applied voltages. It is helpful in selection of optimum operating conditions and design of experimental setup. Experimental results demonstrate that the pulse-waveform can be used to reduce the frequency drift by shorting the beating time.