Demonstration and Fabrication Tolerance Study of Temperature-Insensitive Silicon-Photonic MZI Tunable by a Metal Heater

We present a temperature-insensitive tunable silicon-photonic Mach-Zehnder interferometer (MZI) filter fabricated by deep ultraviolet lithography. The wavelength shift of the MZI filter depending on temperature is reduced down to -4 pm/°C at ~1480 nm using a design with waveguide narrowing and widening, and the MZI filter is tunable with a thermal heater at an efficiency of 24 mW/free spectral range (FSR). The FSR of the MZI is about 5.8 nm, which corresponds to a channel spacing of 2.9 nm for a two-channel MZI. We discuss the fabrication tolerance of the fabricated MZI according to experimental and simulation results and show design parameters for a fabrication-tolerant temperature-insensitive MZI with a 20-nm channel spacing for coarse wavelength-division multiplexing application.