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介质涂层覆盖微电子机械系统(MEMS)可变形反射镜(DM)阵列的能力。微机械加工的DM提供了前所未有的光束控制，然而，由于典型的金属光学涂层的反射率相对较低，它们无法在几百毫瓦的激光下持续运行。根据这项研究开发的介质涂层MEMS DMS将能够处理数十瓦的激光功率，与许多激光加工应用相称。通常情况下，介电涂层会使基于MEMS的反射镜变得无用，因为这些厚膜中的残余应力会使反射镜表面翘曲。与典型的MEMS层厚度相比，即使是反射率为99.75%的简单单波长涂层也相对较厚(是目标波长的3-5倍)。为了获得高质量的镜面，本研究将制造具有应力补偿层的新型MEMS DMS，以平衡来自介质涂层的残余应力。应力补偿层使DM能够被良好建立和容易获得的涂层所覆盖。带有这些涂层的反射镜将在高激光通量下进行测试，以确定故障点并验证DM的热模型。该项目的更广泛影响/商业潜力是增强微电子机械系统(MEMS)可变形反射镜(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方面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，为使用相对高功率(1-100 W)激光的应用提供精细的波前控制。对于天文学家来说，DM将被用于对大气湍流的激光导星光束进行预补偿，以改善10-30米级望远镜的声光性能。这些性能的提高将使天文学家能够更深入地探索宇宙。同样的技术也可用于增强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通孔钻孔、硅通孔(TSV)、高密度柔性电路的激光加工、电阻的集成电路微调以及DRAM中的链接切割。对于这些应用，DM可以提供快速聚焦校正和动态波束整形，以便为手头的任务量身定制波束。

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.