Design and realization of a widely tunable sampled-grating distributed-Bragg reflector (SG DBR) laser emitting at 976 nm

Tunable laser sources are required in a variety of applications such as absorption spectroscopy, optical communication and coherent optical detection schemes [1]. The tunability of these devices is often based on external cavities, which utilizes movable external gratings to select and tune the wavelength. Another approach of achieving wide wavelength tunability is based on the concept of a sampled-grating (SG), consisting of a periodic sequence of regions with and without a Bragg grating, resulting in a comb-like reflectivity spectrum (see Fig. 1). In a laser having SGs with different sampling periods, and hence different spacing of the reflectivity peaks, lasing emission occurs whenever two peaks overlap [2]. Thus by tuning the reflectivity spectra of the SGs, the emission wavelength of the laser can be tuned.