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18 August 2000 Micromachined optical concentrators for IR LEDs
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Proceedings Volume 4179, Micromachining Technology for Micro-Optics; (2000)
Event: Micromachining and Microfabrication, 2000, Santa Clara, CA, United States
One of the most important factors limiting the optical efficiency of LEDs is total internal reflection of generated light, where photons incident to the surface at angles greater than the critical angle are reflected back into the semiconductor and absorbed. Most semiconductors have a large refractive index and hence a small critical angle. Narrow gap semiconductors, such as InSb, have particularly large refractive indexes and corresponding smaller critical angles. Additionally, strong absorption of light in the 3-5(mu) m range means that epoxy immersion lenses, which are used for GaAs Ir LEDs, cannot be used in InSb based IR LEDs. We have therefore used a novel micromachining technique to fabricate optical concentrators inInSb and HgCdTe layers. Inductively coupled plasma (ICP) etching is used to alternatively eatch the resist mask and the semiconductor, with oxygen and methane/hydrogen respectively, producing concentrators with parabolic profiles. Continuing optimization of the process to reach the theoretical limits of optical gain is described together with some of the main issues associated with the fabrication process.
© (2000) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Geoff R. Nash, Tim Ashley, David T. Dutton, Neil T. Gordon, and T. J. Phillips "Micromachined optical concentrators for IR LEDs", Proc. SPIE 4179, Micromachining Technology for Micro-Optics, (18 August 2000);

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