Vladimir Markov (MetroLaser, Inc.), Shiang Liu (The Aerospace Corporation), Roberta Ewart (AF Space and Missile Systems Center, LAAFB) Douglas Craig (Air Force Research Laboratory)
Keywords: Modeling, Analysis, Simulations
Abstract:
Laser pointing, tracking, imaging/discrimination and engaging (PTIE) of a remote target, such as high-altitude aircraft, satellite, or reentry vehicle, requires for a sufficient level of energy density on surface of the target. Satisfactory laser systems performance has been demonstrated at relatively short distances and low optical aberration and distortion conditions. However, longer range and deep atmospheric turbulence introduce serious challenges for an efficient PTIE function. Solution to the two key technical challenges: (a) very low intensity in a returned signal, and (b) compensation of optical aberrations along the beam path, become critical issues in designing of an efficient PTIE laser system (PTIELS).
Reliable detection of a low intensity return signal requires for a narrow bandwidth high-gain, practically thresholdless amplifier. An extensive analysis of this problem allows to conclude that optimal solution to low intensity signal detection can be achieved by using phase-conjugating amplifiers (PCA). Moreover, the PCA as the mirror in a laser system leads to compensation of optical wavefront aberrations in real time. Optimal performance of such a system can be attained with the PCM operating in the Brillouin-Enhanced Four-Wave Mixing (BEFWM) scheme.
We report on the results of the analysis and experimental studies of the PTIELS brassboard design with the BEFWM. The system allows coherent thresholdless detection and amplification of an ultra-low intensity target-scattered signal with the gain (up to 100 db) with complete phase conjugation of its wavefront. As result, the PTIELS output is the amplified signal beam that holds the information that is essential for target characterization, i.e. its speed and scattering characteristics of its surface. Moreover, because of the coherent nature of signal detection, this technique enables for measuring the atmosphere-introduced aberrations of the transmitted wavefront and their real-time compensation with adaptive optics methods.
The presented results of an extensive theoretical analysis and experimental studies illustrates that the BEFWM-based approach allows for an end-to-end solution to the problem of a remote target pointing, tracking, imaging and engaging and outlines roadmap for its practical implementation.
Date of Conference: September 12-15, 2007
Track: Modeling, Analysis and Simulations