Polymer/Silica Hybrid Waveguide Bragg Grating Fabricated by UV-Photobleaching

A polymer/silica hybrid waveguide Bragg grating fabricated through an ultraviolet-photobleaching method is proposed. Periodic surface corrugation on the lower silica cladding layer is induced by contact lithography and inductively coupled plasma etching. A Bragg grating with a large area and period Λ = 3 μm was formed. The grating structure is transferred onto a polymer film by spin coating a negative UV photoresist (SU-8 2005) on the lower silica cladding layer. A channel waveguide is formed using the UV-photobleaching method. This configuration along the channel waveguide gives rise to strong resonance in a 7.5-mm Bragg grating. We achieve a transmission peak with an extinction ratio of 7.3 dB and a 3-dB bandwidth of 0.5 nm. The shift of the reflection peak with temperature over the range 25 °C-35 °C is 1.5 nm. This temperature dependence exhibits an average slope of -0.15 nm/°C.