A line-shaped heater and an optical resonator with portions on opposite sides of the line-shaped heater are provided. In particular a device provided herein includes: one or more inputs; one or more outputs; one or more optical waveguides configured to: receive an optical signal from at least one of the one or more inputs; and convey the optical signal to at least one of the one or more outputs; an optical resonator configured to modulate or filter the optical signal; and a heater configured to heat the optical resonator, the heater being line-shaped and having a first side and a second side opposite the first side, and the optical resonator comprising a first portion at the first side of the heater and a second portion at the second side of the heater.