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 delayed optical heterodyne method. It is the first time to our knowledge to study in detail the dynamic characteristics of the SG-DBR laser which is phase-section tuned by a square-waveform voltage. ► 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. ► The investigation of the linewidth broadening helps us to further understand the instantaneous optical properties of the laser. It is useful for better assessing and selecting the DBR lasers.