Tech Briefs

Novel photoactive compounds, solutions, and nanocomposites have been studied.

Air Force Research Laboratory, Wright-Patterson Air Force Base, Ohio Aprogram of research has addressed multiple topics in the design, development, characterization, and utilization of new materials for photonic applications. These materials include compounds, solutions, and nanocomposites that exhibit diverse types of single- and multiple-photon activity. The accomplishments of this research can be grouped into four main categories and summarized as follows:

The Generic Molecular Structure depicted here represents three different species (A, B, C) of two-photon-absorbing nickel(II) chelated 1,10 phenanthroline-containing chromophores.
  1. Multiphoton-absorbing materials for applications in which there are requirements to limit and stabilize optical power.

    Accomplishments in this category include investigation of degenerate nonlinear absorption and optical-power-limiting properties of asymmetrically substituted stilbenoid chromophores; synthesis and characterization of novel two-photonabsorbing, 1,10-phenanthroline-containing, p-conjugated chromophores and nickel( II)-chelated complexes thereof (see figure) with quenched emissions; synthesis and characterization of two- and three-photon- absorbing novel fluorene-containing ferrocene derivatives; synthesis and testing of novel-conjugated dendritic nanosized chromophores with enhanced two- and three-photon absorption; and demonstration of limiting and stabilization of optical power by use of novel two-photon-absorbing liquid dye salt systems. The major advantage of using a neat liquid dye salt as the two-photon-absorbing medium is that the concentration of two-photon-absorbing chromophores is unusually high (of the order of 1 M) and it can withstand a relatively high-input laser power and energy.

  2. Advanced materials for photorefractive and electro-optical devices.

    Accomplishments in this category include demonstration of efficient photosensitization and high optical gain in a quantum-dot sensitized hybrid photorefractive nanocomposite at the telecommunication wavelength of 1.34 μm; design of new organically-modified-silica precursor material systems for electro- optical devices; and demonstration of photoconductivity and photorefractivity at infrared wavelengths in hybrid nanocomposites.

  3. Novel organic dyes for multiphoton-pumped frequency-up-conversion lasing.

    Two-, three-, and four-photon-pumped stimulated emission (cavityless lasing) properties of ten stibazolium dyes in solution were studied comprehensively.

  4. A new type of stimulated Rayleigh-Bragg scattering generated in a novel two-photonabsorbing- dye solution.

    This scattering is, more specifically, a two-photon-excitation-enhanced backward stimulated Rayleigh scattering. This stimulated scattering shows no frequency shift, and therefore, is different from most other known stimulated scattering processes. The principle of this effect can be highly useful for optical phase conjugation and optical-power limiting.

This work was done by Paras N. Prasad and Guang S. He of the University of Buffalo for the Air Force Research Laboratory.

AFRL-0044

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