Thermo-optic tunable grating structure for coupler and radiator applications in silicon

We propose tunable grating structures implemented by the change of the effective refractive index based on thermo-optic effect in silicon. For resistive heating, p-i-n or pn junction was formed in the grating region and surrounding region was thermally isolated. Fabricated tunable gratings were characterized by fiber-to-fiber measurement and Fourier-imaging system with a variation of the bias voltage applied to the heater. From a p-i-n type structure showing the best data, we achieved a wide tuning of the central wavelength in a range of 40 nm with an efficiency of 0.41 nm/mW. When this tunable grating structure is applied in the radiator of the optical phased array, the radiation angle was actively manipulated in a range of 2.7 degrees in the longitudinal direction.