To overcome thermal distortion and spherical abberation issues of high-power ZnSe optics, a new approach to transmissive-optics design uses two optics in an "air-spaced doublet" arrangement to remove heat axially.
Turbulent-cooling gas, injected at high flow rates in the space between the two optics, reduces the optics absolute temperature. Because the axial-thermal path is shorter, the design efficiently lowers both the internal "lifetime-reducing" stress, and the hoop stress at the edge. A reduced radial thermal gradient virtually eliminates temperature-induced spherical aberration.
With these improvements using the Turbo-Cooled(reg) Optical Assemblies, and infrared window material--ZnSe in particular, but also CdTe, GaAs, and ZnS--withstand much higher power levels than a single optic, while still providing diffraction-limited performance.
Frank Foote, Laser Power Optics, 12777 High Bluff Drive, San Diego, CA 92130, PHONE (800) 262-5273.