SBIR Phase I: Dielectric Coating of MEMS Deformable Mirrors

这个小型企业创新研究（SBIR）第一阶段项目将展示用高反射率介电涂层涂覆微机电系统（MEMS）变形镜（DM）阵列的能力。微机械DM提供了对光束的前所未有的控制，然而，由于典型的金属光学涂层的相对低的反射率，它们不能维持使用超过几百毫瓦的激光器的操作。通过这项研究开发的介电涂层MEMS DM将能够处理数十瓦的激光功率，与许多激光加工应用相称。通常，介电涂层将使基于MEMS的反射镜无用，因为这些厚涂层中的残余应力使反射镜表面翘曲。与典型的MEMS层厚度相比，即使是具有99.75%反射率的简单单波长涂层也相对较厚（感兴趣的波长的3-5倍）。为了获得高质量的镜面，本研究将制造新型MEMS DM，其具有平衡电介质涂层残余应力的应力补偿层。应力补偿层使得DM能够涂覆有成熟且容易获得的涂层。这些涂层的镜子将在高激光能量密度下进行测试，以确定故障点和验证DM的热模型。该项目的更广泛的影响/商业潜力是提高微机电系统（MEMS）变形镜（DM）的能力，使其适用于工业应用。可变形反射镜在空间和时间上提供对光束的高分辨率控制。这种能力导致了天文学，视网膜成像和显微镜的巨大技术和科学进步。这里的研究将扩展低成本MEMS DM的能力，为采用相对高功率（1-100 W）激光器的应用提供精致的波前控制。对于天文学家来说，DM将用于预补偿激光引导星星光束的大气湍流，以提高10- 30米级望远镜的AO性能。这些性能的提高将使天文学家能够更深入地探索宇宙。同样的技术也可以用于电子和半导体行业的激光加工设备。该设备的应用包括陶瓷封装的过孔钻孔、硅通孔（TSV）、高密度柔性电路的激光加工、电阻器的集成电路微调以及DRAM中的链路切割。对于这些应用，DM可以提供快速聚焦校正和实时光束整形，以针对手头的任务定制光束。

This small Business Innovation Research (SBIR) Phase I project will demonstrate the ability to coat a microelectromechanical systems (MEMS) deformable mirror (DM) array with high-reflectance dielectric coatings. Micromachined DMs provide unprecedented control over an optical beam, however, they cannot sustain operation with lasers of more than a few hundred milliwatts because of the relatively low reflectance of the typical metallic optical coatings. The dielectric coated MEMS DMs developed with this research will be able to handle tens of Watts of laser power commensurate with many laser machining applications. Normally, a dielectric coating would render a MEMS based mirror useless because residual stresses in these thick coatings warp the mirror surface. Even simple single-wavelength coatings with 99.75% reflectance are relatively thick (3-5 times the wavelength of interest) compared to typical MEMS layer thicknesses. To achieve a high-quality mirror surface, this research will fabricate novel MEMS DMs with a stress-compensation layer that balances residual stresses from the dielectric coatings. The stress compensation layer enables the DMs to be coated with well-established and readily available coatings. Mirrors with these coatings will be tested at high laser fluence to determine failure points and validate thermal models of the DM.The broader impact/commercial potential of this project is to enhance the capabilities of microelectromechanical systems (MEMS) deformable mirrors (DM) to make them suitable for use in industrial applications. Deformable mirrors offer high-resolution control of an optical beam spatially and temporally. This ability has led to tremendous technical and scientific advances in astronomy, retinal imaging, and microscopy. The research here will expand the capabilities of low-cost MEMS DMs to provide exquisite wavefront control to applications where relatively high power (1-100 W) lasers are employed. For astronomers, the DM will be used to pre-compensate laser guide star beams for atmospheric turbulence to improve AO performance of 10-30m class telescopes. These increases in performance will enable astronomers to probe deeper into the universe. The same technology can be employed to enhance laser-machining equipment for the electronics and semiconductor industries. Applications for this equipment include via drilling for ceramic packages, through- silicon vias (TSV), laser machining of high-density flex circuits, integrated-circuit trimming of resistors, and cutting of links in DRAMs. For these applications, the DM can provide fast focus corrections and on-the-fly beam shaping to tailor the beam for the task at hand.