Physical Sciences Inc. has several ongoing programs to develop novel high-damage-threshold solid-state optical limiters. We are using polymer matrices doped with RSA (reverse saturable absorber) chromophores such as metallo-phthalocyanines to create both a tandem optical limiter and a graded-density limiter. Characterization is performed using a novel f/5 optical setup which simultaneously measures spatial and temporal profiles of the transmitted light as well as the conventional average transmission. A Q-switched doubled Nd:YAG is used as the probe laser. In this paper, we present detailed spatial and temporal characterization of solid-state tandem optical-limiter devices. To our knowledge, few such measurements have been conducted on limiting materials. Our initial results indicate that for these materials, damage typically occurs within two nanoseconds of the damaging pulse. In addition, CCD images reveal the spatial evolution of the nonlinear absorption of the pulse as it interacts with the limiting material at energies ranging from microjoules to millijoules. Lastly, time-resolved damage measurements were conducted on PMMA. These results as well as others which elucidate the limiting and damage dynamics will be presented.
In this paper we discuss vibrational to electronic energy transfer as a potential method for producing a population inversion in atomic iodine. We discuss the background of this approach and a novel, high-flux F atom source integrated into a small scale supersonic reactor. We present data for energy transfer from HF(v) and H<sub>2</sub>(v) to the I atom manifold. Using a sensitive diode laser diagnostic we have probed the ground state manifold atomic iodine and observed that the absorption on the I atom line could be reduced to an immeasureably low value. We also describe a novel, diode laser based imaging diagnostic that will have important applications in future chemical or electrical laser development.
This paper presents results from investigations of mixing flowfields and optical gain profiles in HF chemical laser systems by infrared hyperspectral imaging. A chemiluminescent F + H<sub>2</sub> reacting flowfield, produced in a high-fluence microwave-driven reactor, was imaged at a series of wavelengths, 2.6 to 2.9 μm, by a low-order, spectrally scanning Fabry-Perot interferometer mated to an infrared camera. The resulting hyperspectral data cubes define the spectral and spatial distributions of the emission. High-resolution images were processed to determine spatial distributions of the excited state concentrations of the product HF(v,J), as well as spatial distributions of small-signal gain on specific laser transitions. Additional high-resolution Fourier transform spectroscopy and spectral fitting analysis determined detailed excited state distributions in the reacting flowfield. The measurements confirm that our reactor generates inverted populations of HF(v,J).
The THz spectra of the high explosives, HMX, RDX, PETN, and TNT were measured using the technique of Time Domain THz (TD-THz) spectroscopy, and resonances attributed to phonon bands were observed. The TD-THz methods used to obtain these spectra are described and strategies for improved data collection methods are outlined. Concepts for through container DIfferential Absorption Lidar (DIAL) are outlined and the suitability of TD-THz methods for DIAL sensing is discussed.