Double-patterned waveguide resonators with conventional UV contact lithography

We propose a method for fabricating integrated microresonators using conventional ultraviolet contact lithography. By a double-patterning scheme, the bus- and resonator-waveguide can be lithography-patterned individually with a single photoresist spinning and etching process. A sub-µm gap is achieved between the bus- and resonator-waveguides, which exceeds the resolution limitation between patterns of the conventional contact-lithography process. The quality (Q) factor of waveguide resonators can be up to ≈10⁴, while the maximum measured extinction ratio of the resonator is larger than 20 dB. This double-patterning method offers easy fabrication, low cost, and sub-µm pitches for silicon photonics.