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There are limited fiber-based single-mode laser sources over the visible and near infrared range. Nonlinear conversion through four-wave mixing in photonic crystal fibers allows for the generation of new wavelengths far from a pump wavelength. Utilizing an all-fiber spliced configuration, we convert 1064 nm light into a W-level signal in the 750 nm – 820 nm spectral region. We demonstrate over 7.9 watts in the signal band, out of a custom photonic crystal fiber with M2

The chalcogen glasses (i.e., glasses based on the elements S, Se, and Te) are transparent in the infrared (IR), possess low phonon energies, are chemically durable, and can be drawn into fiber. We review our recent research progress at the Naval Research Laboratory (NRL) to develop chalcogenide glass fibers for applications in the mid- and long-wave IR wavelength regions from 2 to 12 μm. Our recent effort in the development of low loss chalcogenide fibers, by describing the synthesis and purification methods, fiber drawing techniques, and highlighting the best results, is summarized. Various applications of these high quality chalcogenide fibers, including multimode beam combiners, mid-infrared supercontinuum sources, fiber Bragg gratings, fiber bundles for IR imaging, anti-reflecting surface structures, and modal filters, are described. Novel infrared (IR) lenses that enable a reduction in the size and weight of IR imaging optics through the use of layered glass structures with broad IR transmission are also presented.

A modified Barium Gallo-Germanate glass has been developed as an exit window for high energy lasers operating in the mid-infrared wavelength region. All the physical properties, for application as a window for high energy laser systems have been measured. Absorption loss and thermo-optic coefficient were identified as key in developing the Barium Gallo-Germanate glass for high energy laser applications. A purification method was developed to reduce the absorption loss of the glass from 6x10(-2) cm(-1) to 2x10(-3) cm(-1) at 3.8 mum. Manufacturability in large size windows has been demonstrated with the fabrication of an 18" diameter prototype window. Modified Barium Gallo-Germanate glasses have also been developed with lower thermo-optic coefficient resulting in lower optical path distortion.

The U.S. Naval Research Laboratory (NRL) has developed two unique materials with excellent properties for various military and commercial applications in the UV-Vis-IR wavelength range. These materials are: an amorphous Barium Gallo-Germanate (BGG) glass and a polycrystalline Magnesium Aluminate Spinel. The BGG glass is made using traditional glass melting techniques, and was developed as a low cost alternative to the currently used window materials. Large prototype windows have been fabricated for a Navy reconnaissance program. BGG windows have been successfully tested for environmental ruggedness (MIL-F-48616) and rain erosion durability up to 300 mph. BGG glass is currently under development and evaluation for High Energy Laser (HEL) applications. A new process has been developed to sinter spinel to clear transparency with very high yields. This process has been used to make various sizes and shapes (flats and domes) and is readily scalable to industrial sizes to produce large windows & domes for various applications. NRL has also developed modified BGG glasses, which are compatible with Spinel and ALON substrates for bonding.

Fiber-based multimode combiners allow for wavelength and power scaling of laser sources while maintaining a common emission aperture and divergence. For applications in the mid-infrared spectral band, chalcogenide glass optical fibers are one of the few alternatives with high-power beam delivery. We demonstrated a 7 × 1 multimode fiber combiner based on a sulfide-based multimode chalcogenide fiber with 76% per-port transmission. Wavelength combining and power scaling in the mid-infrared are demonstrated through the fiber combiner.

Barium gallogermanate (BGG) glasses are currently being explored as a viable low cost material for numerous U.S. defense and commercial visible-infrared window applications. These glasses are transparent from 0.4 mum to beyond 5.0 mum and can be easily made in large optics and complex shapes with high index homogeneity. For high-energy laser (HEL) applications, knowledge of the thermo-optic coefficient (dn/dT) of the window material is important in determining the optical path distortion. The dn/dT measurements were made on BGG glass at 633 and 3390 nm and compared with the values for multispectral ZnS. The dn/dT for BGG glass was approximately 1/5 the value for multispectral ZnS, giving BGG glass a clear advantage for HEL applications.