AVS 46th International Symposium
    The Science of Micro-Electro-Mechanical Systems Topical Conference Thursday Sessions
       Session MM+MI-ThM

Paper MM+MI-ThM11
Microfabricated Low-Power Broad-Band Light Source Utilizing Tungsten Filaments

Thursday, October 28, 1999, 11:40 am, Room 620

Session: Processing and Integration Technology
Presenter: E.W. Jones, JPL-California Institute of Technology
Authors: E.W. Jones, JPL-California Institute of Technology
T. George, JPL-California Institute of Technology
M.L. Tuma, NASA-Glenn Research Center
R. Hansler, Lighting Innovations-John Carroll University
Correspondent: Click to Email
A miniature,Si chip-based, incandescent light source utilizing tungsten filaments is being developed for integration into fiber optic systems to wavelength multiplex a suite of fiber-optic sensors operating in harsh environments from -50 C to 600 C. The requirements for the light source are that it operate at 2800 K, with an output power >100 mW in the 500-900 nm spectral band with spectral power variance of no more than 4% over the spectral band. In addition, it should be rugged, long-lived, with an output stabilization time of about 1 second, and have a "footprint" comparable to LED devices. Other uses for these filaments are automobile headlights, and systems for vehicle navigation, in remote applications such as monitoring bridges for stress, and industial plant monitoring. To date, several filament fabrication approaches are being attempted. The first uses sputtered tungsten films (1-2 microns thick) patterned in various filament geometries. These filaments have been operated at <<1500 K. The operating temperature of these filaments is limited because they cannot be made free-standing and have to be supported by SiN membranes due to the high intrinsic stress in the tungsten films. A second approach that has been more successful in achieving higher temperatures (> 2200 C) is the mounting of coiled-coil wire filaments on microfabricated Si chips. Lastly, 25-micron-thick W sheet stock is being patterned to produce planar spiral filaments. Filaments satisfying the above criteria will be packaged into a hermetically sealed three-chip stack consisting of a bottom reflector chip, a middle filament chip, and a top 5 mm x 5 mm SiN membrane optical window chip, integrated with an optical fiber. The fabrication procedures as well as the optical and electrical characterization results will be discussed in detail.