(LWIR) / mid-wave infrared (MWIR) multispectral applications.

 

DESCRIPTION: In the last 20 years, significant strides have been made in new growth methods for near-net shapes (e.g., edge-defined film-fed growth), treatments (e.g., anti-erosion coatings), and materials (e.g., ceramics, spinels) for use in mid-wave (MW) and short-wave (SW) infrared (IR) windows and domes. During the same period, almost no investment has been made to expand the availability of materials for LWIR use, and the number of available U.S. suppliers for relevant processes and coatings has dwindled. A single LWIR germanium dome for military applications can cost over $200K, can take up to one year to produce, and may require post-processing and/or coatings and treatments from foreign vendors. Innovative sources and methods are sought for new materials, growth techniques, and/or treatments to enable production of multi-spectral (MWIR through LWIR) windows and domes to 10 inches across, with strength and optical properties equal to or exceeding those made of germanium for under

$50K per item.

 

PHASE I: Identify novel manufacturing methods and/or new treatments/materials to permit development of a dual- band (MWIR/LWIR) dome/window with optical and physical strength characteristics to meet or exceed those made of germanium. Ensure that selected methods and materials have no intrinsic limitations to scaling to sizes of 100 square inches (window) or 10 inches in diameter (hemispherical dome). The Phase I effort will include prototype plans to be developed under Phase II.

 

PHASE II: Produce an 8-inch (minimum) diameter hemispherical dome suitable for use in LWIR optical systems (with nothing to preclude extension of the technology to larger sizes and to MWIR/LWIR dual-band use) with optical transmission, wavefront error, physical strength, and water solubility performance capabilities meeting or exceeding performance of .25" thick single-crystal germanium, at a per-unit cost below $50K.

 

PHASE III DUAL USE APPLICATIONS: Produce and provide antireflection coatings, and characterize the optical performance of five hemispherical domes of a to be specified diameter less than 8 inches. Demonstrate (1) optical transmission greater than 70% in both the mid-wave and long-wave optical bands, with optical transmission loss and wavefront error less than or equal to that observed, and (2) scratch and rain erosion resilience equal to or greater than that observed, for 0.25-inch-thick germanium slabs of the same thickness. Ensure that domes exhibit transmission to temperatures of 120°C and 12 microns, with target per unit cost of below $50K and production lead time less than 5 months.

 

Successful technology development would have applications in commercial photonics and thermal analyses. This technology will have applications in any dual-band infrared remote sensing application. Specific potential applications include identifying crop/vegetation types, assisting law enforcement in identifying illegal crop types/locations, environmental sensing, wildfire mapping, chemical dispersion mapping, or pollution/contrail assessment. Broad categories of industries that may benefit include petroleum (for assessing types of geological formations), agriculture, and ecological/biological industries.

 

REFERENCES:

1.   Bayya, S., Sanghera, J., Kim, W., Villalobos, G., and Aggarwal, I. “Recent Advancements in Multiband IR Sensor Windows.” Optical Components and Materials IX 2012. SPIE Proceedings: San Francisco https://www.spiedigitallibrary.org/conference-proceedings-of-spie/8257/1/Recent-advancements-in-multiband-IR- sensor-windows/10.1117/12.910149.short

 

2.   Chalmers, B., Labelle Jr., H., and Mlavsky, A. “Edge-defined, film-fed crystal growth.” Journal of Crystal Growth, 1972, pp. 84-87. https://www.researchgate.net/publication/244248521_Edge-defined_film- fed_crystal_growth

 

3.   Harris, D. Materials for Infrared Windows and Domes. Society of Photographic Instrumentation Engineers, 1999. https://spie.org/publications/book/349896?_ga=2.83614613.2031369234.1531401978- 259269508.1531313709&SSO=1