KOSEN 한인과학기술자네트워크

Remote Sensing and Directed Energy Applications of Femtosecond, Terawatt Lasers. Primary Sponsor: Department of Defense Deadline: 4/11/2001 KEYWORDS TECHNOLOGY AREAS: Chemical/Bio Defense, Sensors, Electronics, Weapons OBJECTIVE: Recent experiments have shown that terawatt, femtosecond laser pulses can propagate up to 12 km in the air. This constitutes a several order of magnitude increase in the propagation distance for high power lasers. The large distance makes possible the development of a new type of remote LIDAR (Light Detection And Ranging) system for the detection of biological and chemical agents at far distances. In addition, these pulses may initiate damage in sensor devices, which could be implemented as counter measures. With current technology, such laser systems can be made compact and man-portable to be used in the field. However, the long-range propagation phenomenon, which involves the rapid dynamics of the strong interaction of the laser field with the atmosphere, is very new and the underlying physics is not well understood. In order to appropriately tailor and control the propagation, a theoretical physics program is needed for the development of a model that quantitatively describes the phenomenon. In addition, the model needs to be verified both with existing data, and also through experiments directly supporting the above applications. DESCRIPTION: The long-range propagation in air of intense (~10 GW/cm2), short (<200 fsec) pulses has been a subject of significant interest since its discovery about five years ago. The laser beam self-focuses to a few hundred micrometers in diameter and maintains its power density and temporal structure over long distances. The stable self-channeling prevents optical breakdown. In addition, the strong self-phase modulation produces spectral broadening from the near-UV through the near-IR, and the spectrum exhibits a high, nearly invariant, degree of spectral coherence. Thus, the term "white light laser" has been coined. Because of the high intensity and large propagation distance, the phenomena has great and versatile potential as a novel white light LIDAR and sensor countermeasure. A key aspect of the phenomena is the formation of individual filaments as the initial pulse power is increased beyond a threshold value. The optical filament can form a tight bundle that propagates over long distances. To control the propagation, it is necessary to understand the filamentation and propagation physics in terms of system parameters and initial and boundary conditions. PHASE I: Develop a physics based numerical and analytical propagation model that includes the strong interaction of the laser pulse with the medium. This should include a verifiable analysis of the detailed transverse instabilities, filamentation, coherence and beam pointing fluctuations as a function of initial conditions such as pulse width, beam radius, wave-front divergence and frequency chirp. PHASE II: Utilize the understanding of the long-range spatial-temporal dynamical evolution and phase coherence to experimentally demonstrate the applicability of the phenomenon to sensor countermeasures and to remote sensing of chemical and biological agents. PHASE III DUAL USE APPLICATIONS: The resulting model and experimental verification will serve as the foundation for novel LIDAR systems for remote detection of atmospheric chemicals and aerosols for pollution monitoring, and for the remote measurements of atmospheric turbulence for improved wind-shear alerts for landing aircraft. REFERENCES: 1. N. Akozbek, C. Bowden, A. Talepour and S. Chin, Phys. Rev. E 61, 4540 (2000). 2. N. Akozbek, C. Bowden, A. Talepour and S. Chin, Laser Physics, 10, 101 (2000). 3. A. Braun, G. Korn, X. Liu, D. Du, J. Squier, and G. Mourou, Opt. Lett. 20, 73 (1995). 4. Uwe Brinkmann, Laser Focus World, 35, November (1999). KEY WORDS: Long-range femtosecond laser propagation; ultrashort laser pulse propagation; white-light laser; remote chemical/biological agent detection DoD Notice: Between January 2 and February 28, 2001, you may talk directly with the DoD scientists and engineers who authored the solicitation topics, to ask technical questions about the topics. The Topic Author is listed in the box below. For reasons of competitive fairness, direct communication between proposers and topic authors is not allowed after February 28, 2001, when DoD begins accepting proposals under this solicitation. Technical Point of Contact: David Skatrud,br> Phone: 919-549-4313 Fax: 919-549-4384 Email: skatrud@arl.aro.army.mil 2nd Technical Point of Contact: Chuck Bowden Phone: 256-876-2650 Fax: 256-955-7216 Email: cmbowden@ws.redstone.army.mil After February 28, 2001 proposers may still submit written questions about solicitation topics through the SBIR/STTR Interactive Topic Information System (SITIS). If you have general questions about DoD SBIR program, please contact the DoD SBIR Help Desk at (800) 382-4634 or email to SBIRHELP@teltech.com. NOTE: The Solicitations listed on this site are copies from the various SBIR agency solicitations and are not necessarily the latest and most up-to-date. For this reason, you should use the agency link listed below which will take you directly to the appropriate agency server where you can read the official version of this solicitation and download the appropriate forms and rules. The official link for this solicitation is: http://www.acq.osd.mil/sadbu/sbir/sttr01/dod_sttr01.htm. DoD will begin accepting proposals on March 1, 2001. The solicitation closing date is April 11, 2001.