Solid-state lasers with tunable output properties enabled by MEMS mirrors

  • Alan Paterson

Student thesis: Doctoral Thesis

Abstract

The use of micro-electro-mechanical systems (MEMS) as intracavity elements in lasers has grown in interest in recent decades. A variety of MEMS mirrors have recently been shown to provide miniaturized alternatives to conventional Q-switch devices. They have the potential to reduce system cost through batch fabrication and reduce the electrical power demand of such systems. The aim of this thesis was to investigate the novel use of MEMS mirrors within solid-state lasers as intracavity tuning elements.The MEMS mirrors used for this work were fabricated using a commercial multi-user process that has been used and characterized extensively by the Centre for Microsystems and Photonics. Two MEMS mirror designs were investigated: one with four electrothermal (ET) actuators and one with an electrostatic (ES) comb-drive actuator. Both mirrors could be driven at their mechanical resonance to result in resonant scanning, while the ET mirror could also be tilted to a fixed angle. The ES mirror movement occurred on one axis while the tilt angle of the ET mirror could be controlled on two axes due to the radial positioning of the four ET actuators. Both mirrors were optically coated after fabrication to enhance their reflectance in the near infrared.The fabricated MEMS mirrors were investigated as intracavity tuning elements for three solid-state laser concepts. The first was a Q-switched Nd: YAG laser with tunable temporal characteristics enabled by separate actuation of two MEMS mirrors. The second was an Yb: KGW laser with tunable output wavelength enabled by a prism and an ET mirror in the Littman configuration. The third was a Q-switched Yb: KGW laser with tunable output wavelength and pulse duration enabled by dual-axis actuation of a single ET mirror combined with a prism in the Littman configuration.To my knowledge, the above-mentioned investigations are the first of their kind and show clear potential for the advancement of MEMS in solid-state laser technology. Such lasers could be appealing for biomedical and automotive applications such as photoacoustic imaging and lidar. Development of a reliable method to deposit a high-reflectance coating on the surface of the MEMS mirrors would also enable power-scaling of the laser output, making the concepts compatible with defence and manufacturing applications such as range finding and laser processing.
Date of Award20 Sep 2019
Original languageEnglish
Awarding Institution
  • University Of Strathclyde
SponsorsEPSRC (Engineering and Physical Sciences Research Council)
SupervisorDeepak Uttamchandani (Supervisor) & Walter Johnstone (Supervisor)

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