Design of Two-Dimensional Sampling Structures for DFB Laser With Tilted Grating

Two-dimensional (2D) sampling structures based on tilted Bragg grating (TBG) for distributed feedback (DFB) laser are proposed and demonstrated. The phase-matching condition of the 2D sampled grating between grating vectors of basic grating and the Fourier component of sampling structure is systematically elaborated. The lightwave experiences different propagating path in the grating area of various sampled grating, which leads to the different spectra and group delay. The tilted grating and tilted sampling strategy is creatively introduced and the traditional one-dimensional method is extended to 2D, which exhibits flexibility in designing grating. By selecting proper sampling period and angle, uniform Bragg grating (UBG) can also be equivalently realized by the tilted sampled grating, i.e. equivalent UBG. And the bifid dips of TBG in spectra are eliminated, while the group delay of working wavelength is improved significantly. The laser with such sampled grating has lower threshold current than TBG. The proposed scheme provides an extraordinary avenue for designing wavelength-selective devices in both photonic integrated circuits and fiber, especially expanding the functions of sampled grating.