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DIRECTED ENERGY PROFESSIONAL SOCIETY

Abstract: 24-Systems-078

UNCLASSIFIED, PUBLIC RELEASE

(U) Underwater Laser-Induced Plasma for Intermediate Force Acoustic and Optical Applications

(U) NRL has developed techniques to create underwater laser-induced plasma (ULIP). Near-field acoustic source characterization involved high energy lens-focused pulses of a Q-switched Nd:YAG laser. The laser-generated plasma evolves into a superheated vapor (steam) piston, which expands supersonically and launches an intense acoustic shock. The size and shape of this super-heated piston determines the acoustic waveform and energy spectral density (ESD). Using a single laser pulse, we have demonstrated the ability to change the ESD frequency centroid by several orders of magnitude.

(U) In addition to acoustic emission, ULIPs produce intense, broadband (black-body) light emission across the optical spectrum. NRL time-resolved spectroscopy determined that ULIP plasma temperatures approach 1 eV using sub-joule laser pulses, with broadband radiation lasting more than 100 ns. Such bright sources may be useful in a variety of underwater scenarios. This brief will outline demonstrated capabilities, and planned study and optimization of ULIP acoustic and optical generation.

Distribution Statement A. Approved for public release. Distribution unlimited.

UNCLASSIFIED, PUBLIC RELEASE