Guided-Mode Resonant Thermo-Optic Tunable Filters

We experimentally show electrically controlled guided-mode resonant thermo-optic tunable optical filters. We design the devices using numerical methods based on rigorous coupled wave analysis and pattern the structure with a UV laser interferometric lithography system. The fabricated devices consist of subwavelength amorphous silicon (a-Si) gratings along with homogeneous a-Si waveguides on glass substrates. We fabricate deep (~ 120 nm) and shallow (~ 20 nm) grating filters that work in the C and L optical communication bands. We thermo-optically change the refractive index of a-Si using electrical Joule heating to spectrally tune the filters. We achieve 15 and 12 nm spectral tuning for these deep and shallow grating devices, respectively, with a temperature increase of 100 °C.