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Active q-switched Nd : YAG laser using MEMS micromirrors

Bauer, Ralf and Lubeigt, Walter and Uttamchandani, Deepak (2012) Active q-switched Nd : YAG laser using MEMS micromirrors. In: Photon 12, 2012-09-03 - 2012-09-06.

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Abstract

In this paper we present the latest investigation on the use of electrostatic resonantly actuated Micro-Electro-Mechanical Systems (MEMS) micromirrors as active Q-switch elements in diode-pumped solid-state lasers. Micromirror-based Q-switches have the potential to become a low-cost and miniature replacement to traditional acousto-optic and electro-optic Q-switches. The MEMS mirrors were fabricated using a commercial multi-user silicon-on-insulator process with a single 25um thick layer. Using a 200Vp-p signal, the electrostatic comb-drive was actuated to generate a torsional resonant mode of the 0.7mm-diameter silicon micromirror. A maximum full optical scan angle of 39° was measured at a frequency of 8.82 kHz. A 500nm thick gold coating was deposited on the silicon micromirror surface resulting in a measured reflectivity of 87% at 1064nm, therefore enabling intra-cavity laser use. A laser-diode side-pumped Nd:YAG resonator was built using a 3 mirror configuration, with the MEMS micromirror as a cavity end-mirror, and a 20% output-coupler at the other end. Q-switched operation was achieved with average output powers of 65mW at a pulse repetition rate of 17.64Hz. The pulse durations measured at 105 ns was within 5% of the theoretical minimum pulse width expected in this type of laser configuration. The average output power was limited by thermal damage to the gold coating on the micromirror. The latest results on the power-scaling of these lasers, including results achieved using alternative dielectrically-coated MEMS micromirrors, will be presented and the challenges faced by this technique discussed.