Distributed Feedback Laser Based on of Two-Dimensional Sampled Tilted Grating*

Two-dimensional (2D) sampling structures based on tilted Bragg grating (TBG) for distributed feedback (DFB) lasers are proposed and demonstrated. The phase-matching condition between the grating vectors of the basic grating and the Fourier components of the 2D sampled grating is systematically explained. Lightwave experiences different propagation paths within the grating areas of various sampled gratings, resulting in different spectra and group delays. By introducing the innovative tilted grating and tilted sampling strategy, the traditional one-dimensional approach is extended to 2D, providing greater design flexibility. By selecting appropriate sampling periods and angles, an equivalent uniform Bragg grating (UBG) can be realized with the tilted sampled grating, eliminating the bifid dips in the spectra and significantly improving the group delay at the operational wavelength. Furthermore, lasers utilizing these sampled gratings exhibit a lower threshold current compared to conventional TBGs. This proposed method offers a novel approach for designing wavelength-selective devices in photonic integrated circuits and fiber systems, particularly enhancing the functionalities of sampled gratings.