Micro-electro-mechanical tunable vertical cavity surface emitting lasers using metal flexures and a top dielectric stack distributed Bragg reflector

摘要

Several approaches exist for the realization of tunable vertical cavity surface emitting lasers (VCSELs) [1-4] including cantilever VCSELs, membrane VCSELs, and half-symmetric cavity VCSELs. Arrays of tunable VCSELs are expected to play a significant role in near-term optical communication systems that will employ wavelength division multiplexing techniques. In this study we design, fabricate, and characterize tunable "membrane" VCSELs using novel micro-electro-mechanical systems (MEMS) piston micromirror designs that include metal or hybrid metal/dielectric top flexures. The device structures start as conventional 980 nm resonant cavity light-emitting diodes (RCLEDs) with selectively oxidized AlGaO current apertures. We use a photosensitive spin-on polymer (polymethylglutarimide -PMGI) material as the sacrificial material between the RCLED and the upper flexure. Up to seven photolithographic mask steps are used to define/create mesas, anchors, dimples, contact pads, etch holes, etc. The top flexure is typically made from a thin film of metal such as gold, deposited by electron beam. With our larger area geometries, we obtain tuning centered at 980 nm of up to 36 nm with less than 6 Volts.