Optical Interface for Bright-Source Exclusion and Threat Testing in a Cryovacuum Chamber for High Power Laser Sources

OUSD (R&E) CRITICAL TECHNOLOGY AREA(S): Space Technology The technology within this topic is restricted under the International Traffic in Arms Regulation (ITAR), 22 CFR Parts 120-130, which controls the export and import of defense-related material and services, including export of sensitive technical data, or the Export Administration Regulation (EAR), 15 CFR Parts 730-774, which controls dual use items. Offerors must disclose any proposed use of foreign nationals (FNs), their country(ies) of origin, the type of visa or work permit possessed, and the statement of work (SOW) tasks intended for accomplishment by the FN(s) in accordance with the Announcement. Offerors are advised foreign nationals proposed to perform on this topic may be restricted due to the technical data under US Export Control Laws. OBJECTIVE: Develop a Cryovacuum Optical Interface for High-Power Laser Radiation Delivery. DESCRIPTION: The effects on performance and robustness of airborne and space-borne imaging sensors when subjected to high levels of radiation is a critical parameter in system design. Such incident irradiance could be due to nearby bright objects such as the sun, moon, impact flash, or potential threats. A Cryovacuum Interface for High-Power Laser Radiation Delivery is needed to facilitate meeting test requirements. The Space Systems Test Facility at AEDC recently implemented a capability in a space simulation cryochamber which provides collimated beams of radiation that represents the solar and lunar apparent in-band irradiance levels in visible and IR bands. The radiative power of bright sources needs to be projected up to the angular extent of the sun or moon (~0.53 ) as well as point sources with collimated low-divergence output that can be introduced into a cryovacuum chamber and deliver high-level irradiances to a system under test (SUT). Needs also include the projection of bright sources to represent: 1) fast-moving resolved targets with a 2-D scene, 2) off-axis (out of FOV) unresolved objects for exclusion testing, 3) off-axis and/or on-axis threat (out and in FOV) radiation for operate-through testing of imaging sensors with a 2-D scene, and 4) projection of on-axis (in FOV) threat radiation to establish system-level damage thresholds. The delivery system must enable a high throughput of laser energy through the vacuum and cryoliner with minimal losses of radiant power that could be damaging to facility support hardware. An in-situ means of adjusting (from outside the vacuum chamber) and monitoring the optical alignment to mitigate power losses is needed as a part of this system. The basic configuration must accommodate laser wavelengths from visible through the LWIR spectral range, though component variations would be acceptable for different spectral bands to make use of fibers or hollow-core waveguides appropriate for those spectral bands. PHASE I: Demonstrate a proof-of-concept cryovacuum optical interface (ambient to temperatures ~ 80 K) for transfer of infrared (NIR through LWIR) laser power levels of up to 200 W from sources external to the vacuum chamber which provides the means to facilitate alignment and monitor optical throughput for use with silicon fibers, infrared fibers, and hollow-core waveguides. PHASE II: Develop and demonstrate a prototype cryovacuum optical interface (ambient to temperatures ~ 20 K) for transfer of laser power levels of up to 500 W (spectral ranges: UV through LWIR) which provides the means to facilitate alignment and monitor optical throughput for use with silicon fibers, infrared fibers, and hollow-core waveguides. PHASE III DUAL USE APPLICATIONS: This technology will support enhanced test capability for military airborne and space-borne sensors. This Phase III may involve follow-on non-SBIR/STTR funded R&D or production contracts for products, processes or services intended for use by the U.S. Government. REFERENCES: 1. Nicholson, R.A., Mead, K.D., Rogers, J.P., Stevenson, M.L., Steely, S.L., Lowry, H.S., and Schwer, D.J., ""EKV Sensor Off-Axis Rejection Test in the AEDC 7V Chamber Test Facility,"" AEDC-TR-19-S-7, February 2019. Distribution C.; 2. Abraham, E.R.I and Cornell, E.A., Teflon feedthrough for coupling optical fibers into ultrahigh vacuum systems, Applied Optics, Vol. 37, No. 10, pp. 1762ff, 1 April 1988.; 3. Miller, D.L. and Moshegov, N.T., All-metal ultrahigh vacuum optical fiber feedthrough, Journal of Vacuum Science and Technology A 19, 386, (2001); https://doi.org/10.1116/1.1322649.; 4. Nelson, M.J., Collins, C.J., and Speake, C.C., A cryogenic optical feedthrough using polarization maintaining fibers, Review of Scientific Instruments 87, 033111 (2016); https://doi.org/10.1063/1.4943678.; 5. Davidson, I.A., Azzouz, H., Hueck, K., and Boourennane, M., A highly versatile optical fibre vacuum feedthrough, Review of Scientific Instruments 87, 053104 (2016); https://doi.org/10.1063/1.4948394. KEYWORDS: cryovacuum; lasers; laser damage; laser threat; solar exclusion; optical interface; vacuum chamber