Design of free-standing GaN strip waveguide and grating couplers

Gallium Nitride (GaN) based fully cut through free-standing planar photonic device was presented. Waveguide, grating couplers and supporting structure were designed by analytical calculation and finite element method (FEM) simulation. Optimized crossing structure and grating coupler with 0.4 dB intersection loss and 1 dB coupling loss at telecommunication band was obtained respectively. Mechanical stability was optimized by static and modal structure simulation. This work illustrates the potential of free-standing GaN photonic structure which will enable new functions for planar photonic devices. It also provides the possibility of monolithic integration of planar photonic and light sources on III–V active platforms.