AVS 51st International Symposium
    MEMS and NEMS Tuesday Sessions
       Session MN-TuM

Paper MN-TuM9
Suspended Waveguide-Based Tunable Integrated Optical Filters on Indium Phosphide MEMS Platform

Tuesday, November 16, 2004, 11:00 am, Room 213C

Session: MEMS and NEMS: Enabling Tools for Scientific Research
Presenter: M. Datta, University of Maryland, College Park
Authors: M. Datta, University of Maryland, College Park
M.W. Pruessner, University of Maryland, College Park
D.P. Kelly, University of Maryland, College Park
R. Ghodssi, University of Maryland, College Park
Correspondent: Click to Email
We propose widely-tunable planar-waveguide-based integrated optical filters on a monolithic InP platform with on-chip parallel-plate capacitive MEMS actuation as the tuning mechanism. These compact (2 mm x 1 mm), fiber-coupled, batch-fabricated filters are perfectly suited for low-cost wavelength division multiplexing optical networks. Each device consists of a moving input waveguide, a fixed output waveguide, deep-etched (>5 micron) Distributed Bragg Reflector (DBR) input and output mirrors integrated with the waveguides, an orthogonal suspension-beam, and a pair of fixed electrodes. All the components are processed monolithically using projection photolithography and methane/hydrogen reactive ion etching, followed by a sacrificial etching step in order to render the input waveguide movable as well as to prevent optical losses due to substrate-leakage (the suspended waveguide approach). InP is etched in multiple cycles, periodically removing the polymer by-products with oxygen plasma to ensure vertical sidewalls with acceptable roughness (<50 nm). By moving the input mirrors electrostatically, we realize a variable-length Fabry-Perot tunable cavity. The filters are designed to demonstrate an wavelength tuning range of 340 nm (1270-1610 nm) with the applied voltage below 10 V. The novel micromachined semiconductor/air-gap DBR mirrors provide a broad high-reflectivity spectrum. Single-stage filters with structurally-stable higher-order DBR mirrors exhibit a full-width-half-maximum (FWHM) of 60 nm. Filter Q-factor can be improved by expanding the input beam or cascading multiple filters. We will present preliminary results for design and fabrication of these devices.