Pencil-like periodic ridges under second Bragg incidence as dual-function beam separation

Abstract

A reflective dual-function pencil-like grating under second Bragg incidence is proposed in this paper. The finite element analysis method is chosen to be the research technique of this grating. Based on it, the influence of the incident angle, period, duty cycle, incident wavelength, and other parameters on the diffraction efficiency are analyzed in detail. At an incident laser wavelength of 1.55 μm, for TE polarization, the efficiency of −2nd order is 96.57% so that the proposed grating can be regarded as a single-port high-efficiency reflective grating. For TM polarization, the grating can function as a dual-port grating with the efficiency 46.03% for 0th order and 45.96% for −2nd order. What is more, the proposed grating has a broader angular bandwidth compared with other dual-function gratings, which ensures the diffraction performance of the grating while allowing some operational changes.