Adaptively Pumped VLA Coated Silicon High Energy Laser Mirror

Historically, the full aperture of a high energy laser mirror has been liquid cooled with enough coolant to handle the peak absorbed thermal flux load over the entire mirror. Previous high energy laser mirrors considered only highly conductive materials and cooling schemes which minimized thermal distortion. Then, the advent of very low absorption coatings and silicon optics provided a laser mirror technology which could withstand high flux loads without liquid cooling. But, in laser weapons systems contamination is a very real concern and ultimately leads to increased absorption. The increased absorption causes increased thermal distortion and reduced beam quality which can greatly reduce beam flux at the target. Increased absorption also causes the mirror surface and valuable VLA coating to heat up, potentially to the point of catastrophic damage. Phase I will demonstrate the feasibility of adaptive pumping. The adaptive pumps contain shape memory elements which sense coolant temperature and once activated by absorbed heat flux, pump coolant into the heat exchanger at a rate proportional to the heat flux. Xray synchrotron systems being developed by Argonne, Brookhaven, National Laboratories require cooled silicon optics to sample the xray beam. These systems currently use cooled mirror with complex coolant systems. The adaptive mirrors will reduce the cost by a factor of 10 and could become standard in xray lithography systems.