Power-Efficient Thermal Optical Tunable Grating Coupler Based on Silicon Photonic Platform

A tunable grating coupler capable of dynamically changing the central wavelength with low power consumption is demonstrated and fabricated using a standard complementary metal–oxide–semiconductor process. The grating coupler is based on an efficient thermal tuning scheme employing free-standing silicon-on-insulator strip waveguides. The air gap provides thermal isolation between the heated grating structure and the underlying silicon substrate, which greatly enhance the heating efficiency. We achieve a thermal shift of 55 nm for the central wavelength with 19.5 mW and a record tuning efficiency of 2.82 nm/mW, which is more than one order of magnitude better than the previous demonstration. The measured rise time and fall time are 0.16 and 0.74 ms, respectively.