Ultraviolet writing of buried waveguide devices in epoxy-coated benzocyclobutene

Abstract

We propose a simple ultraviolet (UV) writing technique for the fabrication of buried waveguide devices, which employs a UV lamp as the light source and commercial benzocyclobutene (BCB) and epoxy OPTOCAST 3505 as the core and cladding materials, respectively. We show that the light emitted from the UV lamp can induce a large refractive-index change (up to 0.012) in BCB, while a negligible index change in the epoxy, which makes possible the writing of buried waveguide devices in BCB by exposing an epoxy-clad BCB film to the UV light through a mask. We demonstrate this technique experimentally with straight channel waveguides, Y-junction waveguide branches, and long-period waveguide gratings. The propagation loss of a typical fabricated waveguide is 1.6 dB/cm at 1550 nm and the polarization-dependent loss is 0.4 dB/cm.