Athermal Narrow-Band Filters Based on Side-Modulated Bragg Gratings

An athermal Bragg grating filter with a narrow bandwidth is proposed and demonstrated. By integrating side-modulated Bragg gratings pillars to silicon-on-insulator slot waveguides, the narrow bandwidth of the wavelength filter can be achieved. With the negative thermo-optic coefficient SU-8 polymer top cladding, the device can be designed to be temperature-insensitive. The proposed Bragg grating filter, with a narrow 3-dB bandwidth around 0.75 nm, can be easily fabricated with only one fully etched step and large corrugation depth. The measured temperature dependence of the fabricated Bragg grating filter is -3 pm/°C.