Heterogeneous integration of a III-V VCSEL light source for optical fiber sensing.

We propose a fiber Bragg grating (FBG) sensor interrogation system utilizing a III-V vertical cavity surface emitting laser (VCSEL) as the on-chip light source. Binary blazed grating (BBG) for coupling between III-V VCSEL and silicon-on-insulator (SOI) waveguides is demonstrated for interrogation of the FBG sensor. The footprint size of the BBG is only 5.62  μm×5.3  μm, and each BBG coupler period has two subperiods. The diameter of the VCSEL's emitting window is 5 μm, which is slightly smaller than that of the BBG coupler, to be well-matched with the proposed structure. Results show that the coupling efficiency from vertical cavities of the III-V VCSEL to the in-plane waveguides reached as high as 32.6% when coupling the 1550.65 nm light. The heterogeneous integration of the III-V VCSEL and SOI waveguides by BBG plays a fundamental role in inducing a great breakthrough to the miniaturization of an on-chip light source for optical fiber sensing.