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Micromachines 2017, 8(5), 134;

In-Plane Optical Beam Collimation Using a Three-Dimensional Curved MEMS Mirror

Department of Electronics and Communication Engineering, Faculty of Engineering, Ain-Shams University, 1 Elsarayat St., Abbassia 11517, Egypt
Si-Ware Systems, 3 Khaled Ibn El-Waleed Street, Heliopolis, Cairo 11361, Egypt
Paris-Est, Laboratoire ESYCOM, ESIEE Paris, Cité Descartes, F-93162 Noisy-le-Grand CEDEX, France
Author to whom correspondence should be addressed.
Academic Editor: Huikai Xie
Received: 25 March 2017 / Revised: 16 April 2017 / Accepted: 18 April 2017 / Published: 25 April 2017
(This article belongs to the Special Issue MEMS Mirrors)
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The collimation of free-space light propagating in-plane with respect to the substrate is an important performance factor in optical microelectromechanical systems (MEMS). This is usually carried out by integrating micro lenses into the system, which increases the cost of fabrication/assembly in addition to limiting the wavelength working range of the system imposed by the dispersion characteristic of the lenses. In this work we demonstrate optical fiber light collimation using a silicon micromachined three-dimensional curved mirror. Sensitivity to micromachining and fiber alignment tolerance is shown to be low enough by restricting the ratio between the mirror focal length and the optical beam Rayleigh range below 5. The three-dimensional curvature of the mirror is designed to be astigmatic and controlled by a process combining deep, reactive ion etching and isotropic etching of silicon. The effect of the micromachining surface roughness on the collimated beam profile is investigated using a Fourier optics approach for different values of root-mean-squared (RMS) roughness and correlation length. The isotropic etching step of the structure is characterized and optimized for the optical-grade surface requirement. The experimental optical results show a beam-waist ratio of about 4.25 and a corresponding 12-dB improvement in diffraction loss, in good agreement with theory. This type of micromirror can be monolithically integrated into lensless microoptoelectromechanical systems (MOEMS), improving their performance in many different applications. View Full-Text
Keywords: curved micromirrors; three-dimensional fabrication; Gaussian beams; surface roughness curved micromirrors; three-dimensional fabrication; Gaussian beams; surface roughness

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Sabry, Y.M.; Khalil, D.; Saadany, B.; Bourouina, T. In-Plane Optical Beam Collimation Using a Three-Dimensional Curved MEMS Mirror . Micromachines 2017, 8, 134.

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