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Proceedings Paper

High-precision beam shaper for coherent and incoherent light using a DLP spatial light modulator
Author(s): Jinyang Liang; Rudolph N. Kohn Jr.; Michael F. Becker; Daniel J. Heinzen
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Paper Abstract

We designed a precision laser beam shaper using a Texas Instruments digital micromirror device (DMD) with a telescope system containing a pinhole low-pass filter. The performance of the beam shaper was measured by comparing the intensity and wave-front uniformity to the target function and by the energy conversion efficiency. We demonstrated flattop and other laser beam profiles with 1-1.5% root-mean-square (RMS) error for a raw camera image and nearly flat phase. A noise analysis of the system revealed that lower error is possible and that most of the error came from coherent speckle noise in the camera. A previous experiment using a 1064 nm single-mode fiber (SMF) laser produced around 7% beam power conversion efficiency. Here we report improvements in system automation and laser source flexibility that result in increasing both the speed of the system to calculate and produce a beam, and the beam uniformity and energy conversion efficiency. A LabVIEW program was written to accelerate the speed of the iterative process for beam profile refinement. A 760 nm super-luminescent light emitting diode (SLED) and a 781 nm Laser Diode (LD) were used as light sources in order to reduce the beam coherence and approach the ultimate performance of the shaper. Both sources greatly reduced the speckle noise and increased measured intensity uniformity. Experiments achieved less than 0.9% RMS error over the entire flattop area with a diameter of 1.32 mm. In addition, simulations were conducted to determine the optimized wavelengths for different types of DMDs. For the .7XGA DMD, the 5th diffraction order matches 750-800 nm. Matching the laser diode to this wavelength increased the power conversion efficiency (input beam to output beam) to 19.8%.

Paper Details

Date Published: 11 February 2011
PDF: 9 pages
Proc. SPIE 7932, Emerging Digital Micromirror Device Based Systems and Applications III, 793208 (11 February 2011); doi: 10.1117/12.870965
Show Author Affiliations
Jinyang Liang, The Univ. of Texas at Austin (United States)
Rudolph N. Kohn Jr., The Univ. of Texas at Austin (United States)
Michael F. Becker, The Univ. of Texas at Austin (United States)
Daniel J. Heinzen, The Univ. of Texas at Austin (United States)

Published in SPIE Proceedings Vol. 7932:
Emerging Digital Micromirror Device Based Systems and Applications III
Michael R. Douglass; Patrick I. Oden, Editor(s)

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