Fabrication of static-alignment fiber-guiding grooves for planar

Abstract

A method for fabricating planar lightwave circuits with at least one static-alignment fiber-guiding groove comprising the steps of: (a) fabricating a sandwiched Si-substrate by forming an etching stop layer on a first Si layer, followed by forming a second Si layer on the etching stop layer; (b) forming a waveguide layer on the Si-substrate, the waveguide layer containing at least one planar waveguide channel buried between a first cladding layer and a second cladding layer; (c) forming a photomask on the waveguide layer so as to allow the fiber-guiding grooves to be fabricated; (d) using the photomask and a first reactive ion etching procedure to form a first portion of the fiber-guiding groove, the first reactive ion etching procedure is controlled such that it etches through the waveguide layer and stops at the second Si layer; and (e) using the photomask and a second reactive ion etching procedure to form a second portion of the fiber-guiding groove, wherein the second reactive etching ion is selected in such a manner that the second reactive ion etching procedure etches only through the second Si layer and stops at the interface between the second Si layer and the etching stop layer. In a preferred embodiment, the etching stop layer comprises a glass material which is resistant to the second reactive etching ion, the fiber-guiding groove is a U-shaped groove, and the waveguide channel has a refractive index which differs from that of the first and second cladding layers by about 0.25%. The etching stop layer provides precise depth control and ensures the repeatibility of light coupling efficiency between the optical fiber and the waveguide, a critical element in lightwave circuits.