Highly efficient thermo-optic phase shifters for UV photonic applications

We propose highly efficient, thermo-optic phase shifters based on aluminum oxide waveguides operating at UV wavelengths. The phase shifters are integrated into Mach-Zehnder interferometers for device characterization. The photonic waveguides are fabricated in a 200 mm CMOS pilot line, and heaters and silicon undercut are defined on the die-level with metal lift-off and dry etching processes. We experimentally demonstrate a phase shifter with an efficiency of 0.85 mW for a π phase shift at 360 nm wavelength. For the bandwidth characterization, we measure the 10 - 90% rise and fall times of a series of phase shifters with varying structural designs and systematically analyze the trade-off between efficiency and response time. The developed device provides a low insertion loss, high-efficiency active modulator that can be readily integrated onto the existing 200 mm aluminum oxide UV photonics platform.