20 May 2015 Ring cavity surface emitting quantum cascade laser with a near Gaussian beam profile
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Abstract
We propose a vertical spiral phase corrector for ring cavity surface emitting (RCSE) quantum cascade lasers (QCLs), which will allow achievement of near-Gaussian generated beam profile. A problem with RCSE QCLs is their donutshaped intensity distribution with a node along the symmetry axis of the ring. This arises because of the π phase difference for the azimuthally polarized rays emitted from opposite elements of the ring. We theoretically demonstrate that near-Gaussian beams can be achieved with a spiral phase shifter that adds one wavelength of additional optical path in going once around the ring. Various three dimensional lithographic techniques for fabricating such a phase shifter, including a grey scale mask, electron-beam resist dose dependency, and two photon induced photopolymerization, are considered. Ring cavity QCLs with the proposed phase corrector will feature better beam quality, larger power, and better resistance to radiative damage in comparison with traditional edge-emitting QCLs.
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Pedro N. Figueiredo, Andrey Muraviev, Robert E. Peale, "Ring cavity surface emitting quantum cascade laser with a near Gaussian beam profile", Proc. SPIE 9466, Laser Technology for Defense and Security XI, 946602 (20 May 2015); doi: 10.1117/12.2175616; https://doi.org/10.1117/12.2175616
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