Low-power variable optical attenuator based on a hybrid SiON-polymer S-bend waveguide.

We propose a low-power variable optical attenuator based on the configuration of a hybrid silicon oxynitride (SiON)-polymer S-bend waveguide and two grooves in both sides of the S-bend waveguide core. With such a configuration, the opposite thermo-optic characteristics of SiON and polymer materials can be fully utilized. As a consequence, the heat utilization efficiency is increased. Theoretical simulation shows that an optical attenuation of ∼50  dB can be achieved with an applied electrical power of 3.6 mW. A typical fabricated device, which has a total length of 8 mm, shows a maximum optical attenuation of 46 dB with an applied electrical power of 16.2 mW and an insertion loss of 5.4 dB.