Blazed subwavelength grating coupler

Short-wavelength mid-infrared (2-2.5 & mu;m wave band) silicon photonics has been a growing area to boost the applications of integrated optoelectronics in free-space optical communications, laser ranging, and biochemical sensing. In this spectral region, multi-project wafer foundry services developed for the telecommunication band are easily adaptable with the low intrinsic optical absorption from silicon and silicon dioxide materials. However, light coupling techniques at 2-2.5 & mu;m wavelengths, namely, grating couplers, still suffer from low efficiencies, mainly due to the moderated directionality and poor diffraction-field tailoring capability. Here, we demonstrate a foundry-processed blazed subwavelength coupler for high-efficiency, wide-bandwidth, and large-tolerance light coupling. We subtly design multi-step-etched hybrid subwavelength grating structures to significantly im-prove directionality, as well as an apodized structure to tailor the coupling strength for improving the optical mode overlap and backreflection. Experimental results show that the grating coupler has a recorded coupling efficiency of -4.53 dB at a wavelength of 2336 nm with a 3-dB bandwidth of & SIM;107 nm. The study opens an avenue to developing state-of-the-art light coupling techniques for short-wavelength mid-infrared silicon photonics. & COPY; 2023 Chinese Laser Press