Light beam profiler and propagation analyzer
| Start date | September 2012 |
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| Client | University College Cork | |
| Investigator | Dr David Nugent |
Abstract
University College Cork (UCC) researchers have invented a method of analyzing the profile and propagation of a light beam using a combination of a digital micromirror device (DMD) and electronically controlled variable focus lens (ECVFL). Based on patents filed by the inventors in 2002, the technology promises important technical and commercial advantages over traditional techniques based on scanning pinholes or slits.
| Beam profiler using transmissive LCD shutter | Beam propagation analyzer using DMD and variable focus lens | |
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DMD scans a knife-edge or pinhole aperture across the beam profile Optical power is detected by two point photodetectors Monitoring photodetectors calibrate fluctuating optical power levels |
Light transmitted through a pixelated LCD shutter Polarisation diversity (not shown) renders profiler polarisation insensitive
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Analog ECVFL and digital DMD profiler via pinhole mode allow the beam waist and thereby M2 parameter to be measured without translating the imaging stage |
Suitable for multimode laser and LED light beams No translation stages or moving knife edges allows high speed profiling Spot photodiodes are wavelength optimised |
Extremely compact design Polarisation diversity allows each polarisation to be analyzed independently |
Motion free operation promises better repeatability, speed and reliability compared to contemporary moving stage designs |
Beam profiler using DMD
A Texas Instruments DMD chip is used to reflect light into a wavelength-optimised photodetector (+θ) or monitoring photodiode (-θ). The latter is used to calibrate for fluctuating beam powers.
The DMD can be mounted on an analog translation stage to increase the scanning resolution. In the example shown below, the lateral resolution was increased from 10 microns (the width of each micromirror) to 2 microns (the incremental translation distance).
Beam propagation analyzer using DMD and variable focus lens
This motion-free laser beam propagation analyzer features a digital micromirror device (DMD) and a electronically controlled variable focus lens (ECVFL). Unlike prior analyzers that require profiling the beam at multiple locations along the light propagation axis, the proposed analyzer profiles the beam at the same plane for multiple values of the ECVFL focal length, thus eliminating beam profiler assembly motion. In addition to measuring standard Gaussian beam parameters, the analyzer can also measure the M2 beam propagation parameter of a multimode beam via the profiler's pinhole mode. Given the all-digital nature of the DMD-based profiling and all-analog motion-free nature of the ECVDL beam focus control, the proposed analyzer promised better repeatability, speed and reliability compared to contemporary mechnical methods.
Documents available for download
Access to the following documents may require subscription to the relevant publication.
| N.A. Riza and M.J. Mughal, "Digital Optical Beam Profiler", US Patent 7,092,079. Provisional application filed 20 March 2002 | |
| N. Riza and D. Jorgesen, "Minimally Invasive Optical Beam Profiler," Opt. Express 12, 1892-1901 (2004). | |
| M. Sheikh and N. Riza, "Motion-free hybrid design laser beam propagation analyzer using a digital micromirror device and a variable focus liquid lens," Appl. Opt. 49, D6-D11 (2010) | |
| Riza, N.A.; Reza, S.A.; , "Broadband All-Digital Variable Fiber-Optic Attenuator Using Digital Micromirror Device," Photonics Technology Letters, IEEE , vol.19, no.21, pp.1705-1707, Nov.1, 2007 | |
| Sheikh, M.; Riza, N.A.; , "Demonstration of pinhole Laser Beam Profiling Using a Digital Micromirror Device," Photonics Technology Letters, IEEE , vol.21, no.10, pp.666-668, May 15, 2009 | |
| Riza, N.A.; All-Digital and Hybrid Analog-Digital Beam Profiling Technology, Photonik International online, March 2008 | |
| Reza, S.A.; Riza, N.A.; , "High Dynamic Range Variable Fiber-Optical Attenuator Using Digital Micromirrors and Opto-Fluidics," Photonics Technology Letters, IEEE , vol.21, no.13, pp.845-847, July 1, 2009 |
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