High average laser power is required for industrial applications such as laser cutting and welding. However, system
performance is often limited by the achievable beam quality and focal length stability, both of which are degraded by
absorption in the transmissive components of the system. We explore in detail the behavior of uncoated and AR-coated
surfaces of Suprasil 3001, Corning 7980, and Spectrosil 2000 fused silica with respect to both surface and bulk
absorption in order to separate substrate effects from coating effects. Ion-beam sputtered AR coatings are shown to
contribute < 0.3 ppm of absorption per coated surface regardless of substrate material, potentially allowing design
flexibility in the selection of substrate materials at the system level.
Chemically Activated Direct Bonding (CADB®) has become widely utilized as an epoxy-free assembly process for solid
state laser crystals in high fluence and other aggressive environments. While data has been presented as to both optical
and mechanical properties of these bond interfaces, previous research has hinted that sample preparation plays a large
part in the final results. Surface finish of samples and any surface defects or sub-surface damage present can lead to
artificially low strength values and other inconclusive results. In the current study, we prepared samples with polished
surfaces to improve the accuracy of the bond strength measurements. Here we present strength data for bonded and bulk
samples of common laser materials such as YAG, phosphate glass, and fused silica.
As optical coatings are deployed in more extreme environments and applications, mechanical and environmental
robustness must be taken into account when designing the film(s). Even minor degradation of the film structure from
these outside factors can affect final fluence handling capabilities in operation, and limit the life of the coating. We
present the results of a study of maximum thermal handling capabilities of Broad-Band IR Anti-Reflective coatings in
the mid-IR (3 to 5 micron) regime. We prepared a family of coated optics utilizing different coating material sets on
different substrate materials, and exposed them to a range of increasing temperatures. We examined the damage
morphologies under dark field, bright field, and Nomarski microscopy.
This paper describes MER's recent advances on the development of high strength, transparent magnesium aluminum
spinel technology for large IR windows and domes. The novel spinel material exhibits high optical and IR transparency
in the 0.2 - 5.5 μm wavelength, is very resistant to abrasion, with density higher than 99.9% of theoretical, with very
fine and uniform grain size, and flexural strength of 300 MPa. Spinel domes technology has been scaled up to produce
hemispherical 180° aperture domes in sizes up to 7" in diameter using freeze casting technology to produce the green
dome preforms. MER is also pursuing the production of large size spinel windows by either producing monolithic large
single windows or by edge bonding several smaller size windows. Both approaches present challenges. Production of
monolithic large size windows is limited by equipment size, availability, and investment capital while the edge bonding
approach requires perfect transparency and strength at the bonded edge. MER together with Precision Photonics Corp.
are developing high strength, edge bonded, transparent magnesium aluminum spinel windows for next generation
aircraft and other defense armor applications which require windows as large as 30"x30"x0.5" at an affordable cost.
MER has further improved strength of the spinel by accurate control of the average grain size and grain size scatter
while remarkable transmission is obtained by elimination of the intergrain/intragrain porosity, and by eliminating all
possible contamination. The spinel bonding technology under development consists of chemically activated direct
bonding (CADB®), an epoxy-free solution-assisted optical-contacting process developed by Precision Photonics
Corporation (PPC).
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