Laser Micromachining of Optical Structures and Surfaces

MLPC is aggressively developing the technological infrastructure for laser micromachining silicon carbide (SiC) mirror substrates to reduce both cost and long lead-times associated with current beryllium optics. During the Phase I STTR effort investigation into the effects of laser micromachining SiC substrates showed that no apparent defects such as microcracks are observed when machining over a wide range of laser processing parameters. This process flexibility allows for a broad range of tunabilty for optimizing material removal rate and surface finish. The key to the success of this effort was the effectiveness of the laser micromachining process coupled with the advantage of high-resolution optical mapping techniques for surface characterization. The focus of the Phase II effort is on developing a closed-loop contour machining process through implementation of high-resolution optical metrology and the development of analysis and control software. The software will analyze the surface contour data, compare it to the corresponding substrate CAD file, determine the volume of material requiring removal, and automatically generate the commands required to complete the machining process. Additionally, a complete metrological record for quality assurance of the substrate surface can be produced before the substrate is removed from the workstation. The proposed contour mapping and control feedback scheme for laser micromachining is not only applicable to SiC mirror substrate fabrication but can be used in a wide variety of other laser machining applications.