Laser Damage Threshold Tester for testing Large Windows and Components for High-Energy Lasers

The effort will develop large optical windows, up to 20-inches diameter, for high-energy laser (HEL) systems in the multiple kilowatt regime. Eliminating surface reflectivity and increasing the laser damage threshold (LDT) for optical components are critical in HEL applications. The UNCC optics group development of high transmittance optical windows with very low loss using anti-reflecting surface structures is a innovative approach compared to traditional surface coatings. This surface nano-structuring eliminates the need for layered, deposited antireflection coatings. Demonstrations of high transmittance (>99%) over wide spectral bands on double-sided processed fused silica windows are possible. This technology has the potential to achieve optical windows for power levels from multiples of kilowatts to megawatts, through collaborative work projects which are currently being funded through NRL (N000173-14-1-G019). Future development shows great potential to transition into optical components that support the future Navy Solid State Laser (SSL) program goals. LDT on large optics offer the potential to be measured at an order of magnitude higher than standard antireflection coatings. The high LDT achieved with this technology is due to the elimination of thermo-mechanically dissimilar coated films, as is typical with current AR coating processes. UNCC and NEL have already achieved this on smaller 4-inch diameter optical windows, of 1mm thickness. Equipment obtained will permit testing of scaled large windows with diameters up to 20-inches, and thicknesses up to 3.5-inches. The proposal requests a high-power laser tester system which will optically test these large diameter windows, without segmenting them to smaller pieces. The acquisition of such test instruments allow UNCC and Navy research groups to expand the training and education of several currently involved US graduate students - as well as expand the current knowledge base in laser optics design. It will also allow UNCC to investigate testing techniques under realistic window form-loading conditions, accommodating optical grade large window LDT measurements for many other DoD applications and optical systems.