N112-140 TITLE: Atmospheric Aerosol Mitigation for High Energy Laser Propagation

TECHNOLOGY AREAS: Weapons

ACQUISITION PROGRAM: PMS 405

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: The principle objective of this effort should improve the overall optical transmission of directed energy (DE) systems operating in a maritime or equivalent environment.

DESCRIPTION: Optical transmission of High Energy Laser (HEL) systems in the Near Infra Red (NIR) optical bandwidth typically suffer from absorption and scattering losses due to water vapor content found in maritime environments. This results in reduced transmission efficiency between the source (laser) and the target (threat) which results in reduced range of defense for ship based systems. Current optical (electromagnetic) technologies exist which if employed in a novel manner may mitigate the absorption/scattering behavior of aerosol content within the beam path of the HEL thereby permitting engagement of targets (threats) at greater distances from platforms (ships). Previous attempts using the HEL beam to "burn" through maritime absorption/scattering environments have resulted with little success in optical transmission improvement due to thermal lensing of the HEL beam. The application of novel principles utilizing either continuous wave (CW) through ultra short pulse (USP) technologies or a combination of said technologies to mitigate the impact of aerosol laden beam paths is desired employing either current technologies or near term development of emerging technologies to achieve substantial improvement in NIR transmission of HEL beams in maritime environments.

PHASE I: Initial work should include model development of typical maritime aerosols and their impact on absorption and scattering at 1070 nm laser energy. The model should further incorporate HEL energy levels with average power of 100 kilowatts (KW) and energy densities of 1 KW/cm2. Techniques for mitigating absorption/scattering impact of aerosols identified in the proposal should be incorporated in the model and demonstrated theoretically as a proof of concept. Identify and design a test instrument for field testing the theoretical concept and mitigation strategy for reducing the impact of absorption and scattering on HEL 1070 nm radiation. The mitigation strategy should be able to handle a beam path that is dynamic; i.e., work in concert with a swept beam and one that has varying elevation angles.

PHASE II: During this phase a prototype system employing hardware and software elements will be completed and subsequently tested in a laboratory environment followed by subsequent testing in a maritime environment. The maritime environment should represent those which Navy vessels would encounter in littoral and open sea conditions with emphasis on high moisture laden atmospheric conditions. Validation of the device must be completed using representative HEL systems or equivalent thereof. Absorption and scattering losses due to water vapor/aerosol content in the beam path should be reduced by at least a factor of two (2) when tested in the wavelength regime of 1050 - 1080 nanometers. Both static testing and dynamic testing of the system will be used to determine the overall success of the technique employed for mitigation of absorption/scattering losses due to aerosols composed of water vapor.

PHASE III: During this phase the small business will oversee and manage the transition of this device to the field and coordinate the efforts with appropriate warfare technology centers such as the Naval Surface Warfare Center - Dahlgren Division. The small business will be responsible for implementing new technologies as they become available towards improved effectiveness of the capability. Device integration with HEL systems should be accomplished by coordinating the mission needs of the warfare center and the technology readiness of the device so as to marry the technologies together minimizing disruption in system advancement. Device production and integration with HEL systems will be driven by available power associated with the integrated HEL system, space requirements, and ship command and control systems. This technology should have value for all services particularly those that are planning to deploy and/or experiment with HEL systems thereby creating opportunity for diversified use within the defense and atmospheric studies community.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: This technology should provide improved signal to noise ratios when employed with Lidar applications due to reduced optical transmission losses for probe wavelengths. In effect, sensing range of Lidar and similar devices should be extended and the resolving power of said devices should be increased as well. The ability to increase sensitivity related to atmospheric probing, be it through Lidar or related optical sensing capabilities, should directly impact the community and services which study environmental effects and impacts of in situ gases and chemistry not normally associated with local environments.

REFERENCES:
1. Handbook of Geophysics.

2. Clouds, Aerosol, and Precipitation in the Marine Boundary Layer - U.S. Department of Energy�s Atmospheric Radiation Measurement (ARM) Climate Research Facility.

3. High Power Laser Propagation - Gebhardt, F. G., Applied Optics, vol. 15, June 1976, p. 1479-1493.

KEYWORDS: laser; aerosol; absorption; scattering; near infrared; high energy laser

** TOPIC AUTHOR (TPOC) **

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