Optical Coatings for High Energy Lasers

Most coatings in high energy lasers are designed for their optical and material properties with little regard to their thermal and mechanical structure. As a result, many HEL components meet exacting reflectivity requirements without the ability to withstand relatively small amounts of heat. This research focuses on developing optical coatings and microstructures that can withstand resonable increases in temperature. The structures maintain their optical shape as well as avoid being damaged by the increase in temperature.

The vast majority of materials undergo a volume expansion when heated, which can cause deformation due to temperature gradients in the structure. An emphasis of this research is into materials such as ZrW₂O₈ that exhibit a volume contraction with increased temperature. ZrW₂O₈ was first synthesized over 40 years ago but we are the first to deposit it as a thin film and measure the negative thermal expansion. Such a coating can be used to control the curvature of a structure as it undergoes thermal cycling.

Additional aspects of the research include studying the heat transfer of MEMS adaptive optic structures.