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12 May 1995 Fabrication of f/0.7 GaP microlens arrays by accelerated mass-transport smoothing in sealed ampoules
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GaP lens arrays have been routinely produced in large formats (substrate dimensions up to 1.5 by 1.0 cm) with high yield and uniformly good finish. Diffraction-limited performance for collimation of single-mode diode lasers has been demonstrated. Laser-diode bars and coherent 2-D surface-emitting arrays have also been collimated with low transmission losses (98%) for 2.5 micrometers > (lambda) > 0.8 micrometers . Microlenses up to 300 micrometers in diameter with f/#s as low as 0.7 have been enabled by a new mass transport fabrication technique using sealed quarts ampoules rather than a flowing tube furnace. In this modification only small pieces of phosphorus are required (no phosphine or hydrogen); consequently, little safety burden is incurred, and initial expenses are reduced. The mesa-step-spacing was increased from 10 micrometers to 15 micrometers , and, by additional chemistry control, 30 micrometers spacings have been demonstrated. Also, time-at-temperature for mass-transport smoothing has been shortened to as little as 8 h. Mass-transport chemical mechanisms and material incompatibilities are discussed. Smoothing in the fused-quartz ampoules is shown to be self- terminated by wafer oxidation, probably caused by oxygen from thermal equilibrium dissociation of the silicon dioxide ampoule. This mass transport technique lends itself to a wide variety of novel lens fabrication strategies and clearly extends the potential applications.
© (1995) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
James S. Swenson Jr., Margaret H. Abraham, and Renny Arthur Fields "Fabrication of f/0.7 GaP microlens arrays by accelerated mass-transport smoothing in sealed ampoules", Proc. SPIE 2383, Micro-Optics/Micromechanics and Laser Scanning and Shaping, (12 May 1995);

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