N121-024 TITLE: Complex Field Wavefront Sensing and Control for Mitigation of Deep Turbulence Effects

TECHNOLOGY AREAS: Sensors, Weapons

ACQUISITION PROGRAM: PMA 242

RESTRICTION ON PERFORMANCE BY FOREIGN CITIZENS (i.e., those holding non-U.S. Passports): This topic is "ITAR Restricted". The information and materials provided pursuant to or resulting from this topic are restricted under the International Traffic in Arms Regulations (ITAR), 22 CFR Parts 120 - 130, which control the export of defense-related material and services, including the export of sensitive technical data. Foreign Citizens may perform work under an award resulting from this topic only if they hold the "Permanent Resident Card", or are designated as "Protected Individuals" as defined by 8 U.S.C. 1324b(a)(3). If a proposal for this topic contains participation by a foreign citizen who is not in one of the above two categories, the proposal will be rejected.

OBJECTIVE: Develop a new, high-energy laser (HEL) sensor system that will simultaneously measure the phase and intensity distributions under the extreme atmospheric turbulence conditions that are common for Navy aircraft and ship-based offensive and defensive applications.

DESCRIPTION: The performance of the Navy�s future HEL directed-energy weapon systems depends on efficient mitigation of atmospheric effects over tactical- and middle-range propagation paths, which are characterized by strong-intensity scintillations. Compensation of turbulence- and thermal-blooming-induced laser beam distortions is commonly associated with the use of adaptive optics techniques originally developed for astronomical applications. Those types of activities are usually conducted at locations and under conditions in which the intensity of scintillations is relatively weak.

In stark contrast, in typical ship and aircraft defense operations, pre-compensation of the turbulence- and thermal-blooming-induced laser beam wavefront phase aberrations are performed under conditions in which the intensity of the scintillations of the target-returned light is strong. As a consequence, conventional adaptive optics techniques are not effective, mostly because of the absence of sensors that are capable of rapidly making simultaneous measurements of the wavefront phase and intensity distributions. In addition, these devices are frequently unable to differentiate between complex field measurement effects that are related to turbulence and those associated with laser beam scattering off the extended target surface (speckle effects).

As such, a novel complex field sensing system that can operate under strong-intensity scintillation conditions is required for the HEL to function optimally. The proposed concept should be capable of real-time retrieval of the target-return complex field characteristics in the presence of strong speckle modulations. In addition, the complex field reconstruction algorithms should be computationally efficient in order to achieve real-time adaptive system operation.

PHASE I: Develop a complex sensor system concept that meets the specified objectives and demonstrate, via analysis and numerical simulations, its ability to do so. Identify critical hardware components and perform a risk assessment.

PHASE II: Develop a prototype and demonstrate its functionality over tactical range distances in atmosphere via laboratory experiments. Conduct studies to establish the potential of making the sensor affordable.

PHASE III: Integrate hardware and software components into a fully functional system. Demonstrate system performance under selected maritime conditions and in civilian applications, e.g., laser communications and active imaging.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: This technology could vastly improve optical�video capabilities that have practical applications in the commercial sector.

REFERENCES:
1. Andrews, L. C., Phillips, R. L., Hopen, C. Y., & Al-Habash, M. A. (1999). Theory of optical scintillation. Journal of the Optical Society of America A, 16(6), 1417-1429. doi: 10.1364/JOSAA.16.001417

2. Majumdar, A. K., & Ricklin, J. C. (2010). Free-space laser communications: principles and advances. New York: Springer Publishing Company.

3. Vorontsov, M. A., Kolosov, V. V., & Polnau, E. (2009). Target-in-the-loop wavefront sensing and control with a Collett�Wolf beacon: speckle-average phase conjugation. Applied Optics, 48(1), A13-A29. doi: 10.1364/AO.48.000A13

KEYWORDS: High-Energy Laser (HEL), Direct Energy Weapon Systems, Strong-Intensity Scintillations, Complex-Field Sensor, Atmospheric Effects Mitigation, Wavefront Sensing

** TOPIC AUTHOR (TPOC) **

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