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Advances in Materials for Photonic Applications

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

Topics:
Composite materials Lasers Materials properties Metals Nanomaterials Nanotechnology Nickel Optics Photonics Research and development Telecommunications
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Advances in Materials for Photonic Applications

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    Defense Tech Briefs Magazine

    This article first appeared in the December, 2007 issue of Defense Tech Briefs Magazine (Vol. 1 No. 6).

    Read more articles from the archives here.

    Overview

    The document presents significant research achievements in the development of multi-photon active materials and novel nanocomposites for opto-electronic technology. It highlights the exploration of nonlinear optical properties, particularly focusing on a two-photon absorbing liquid dye salt system. This system demonstrates superior optical stabilization, effectively reducing the relative fluctuation of nanosecond laser pulses by more than two times when passed through the highly concentrated nonlinear absorbing medium.

    The study utilized a 1-cm long liquid dye salt sample and employed nanosecond 1064-nm laser pulses with a variable repetition rate from 1 to 10 Hz. The research indicates that the power stability of the output laser pulses is significantly better when using a Pockels' cell as an electro-optic Q-switch compared to a BDN dye-doped polymer sheet. The pulse duration was approximately 10 ns with the Pockels' cell and 13-15 ns with the BDN sheet.

    Additionally, the document discusses the phenomenon of backward stimulated scattering observed when the input laser energy exceeded a certain threshold (around 60 µJ or 40 MW/cm²). A Fabry-Pérot interferometer was used to analyze the spectral properties of the stimulated scattering, revealing a spectral resolution of 0.025 cm⁻¹. The nonlinear transmission of the input pump beam and the energy of the backward stimulated scattering were measured as functions of the input laser energy.

    The research also emphasizes the advantages of using a neat liquid dye salt as a two-photon absorbing medium, which allows for a significant increase in effective molar concentration and the ability to withstand higher input laser energies and intensities. Furthermore, a new type of stimulated Rayleigh-Bragg scattering was identified, characterized by two-photon excitation enhanced backward stimulated Rayleigh scattering in a nonlinearly absorbing dye solution, which shows no frequency shift, distinguishing it from other known stimulated scattering processes.

    Overall, the document encapsulates the advancements in nonlinear optical limiting and stabilization techniques, showcasing the potential applications of these materials in telecommunications and other opto-electronic fields. The findings contribute to the understanding and development of materials that can enhance the performance of optical systems.

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