Abstract

Active components on glass and lithium niobate substrates have been fabricated by combining passive waveguides with an overlay of grafted semiconductor material for optical detection applications¹. To improve the overall coupling from an optical fiber to the detector, a vertical directional coupler that transfers power from a buried waveguide (with a minimal insertion loss) to a surface waveguide was recently proposed and demonstrated using a field- assisted K⁺-ion exchange in glass². Though this scheme works well for vertical coupling of light to the detector, its efficiency is impaired by the presence of a thin layer of low index amorphous material at the semiconductor/waveguide bonding interface³. An effective way to avoid this problem is to use edge coupling to the detector which can be achieved by cladding the waveguide/detector structure with a dielectric thin film of refractive index higher than that of the waveguide⁴. Here, we report preliminary results on the fabrication and measurement of a vertical directional coupler that is clad with a sputtered Corning 7059 glass thin film to take advantage of this edge coupling scheme. In addition, we compare the experimental to the theoretical results obtained using a finite-difference vector beam propagation method⁵ (FD-VBPM).

© 1993 Optical Society of America