Researchers at the Army Aviation and Missile Research, Development, and Engineering Center (AMRDEC) have
initiated multidiscipline efforts to develop nano-based structures and components for insertion into advanced missile,
aviation, and autonomous air and ground systems. The objective of the research is to exploit unique phenomena for the
development of novel technology to enhance warfighter capabilities and produce precision weapons. The key technology
areas that the authors are exploring include nano-based microsensors, nano-energetics, nano-batteries, nano-composites,
and nano-plasmonics. By integrating nano-based devices, structures, and materials into weaponry, the Army can
revolutionize existing (and future) missile systems by significantly reducing the size, weight and cost. The major
research thrust areas include the development of chemical sensors to detect rocket motor off-gassing and toxic industrial
chemicals; the development of highly sensitive/selective, self-powered miniaturized acoustic sensors for battlefield
surveillance and reconnaissance; the development of a minimum signature solid propellant with increased ballistic and
physical properties that meet insensitive munitions requirements; the development of nano-structured material for higher
voltage thermal batteries and higher energy density storage; the development of advanced composite materials that
provide high frequency damping for inertial measurement units' packaging; and the development of metallic
nanostructures for ultraviolet surface enhanced Raman spectroscopy. The current status of the overall AMRDEC
Nanotechnology research efforts is disclosed in this paper. Critical technical challenges, for the various technologies, are
presented. The authors' approach for overcoming technical barriers and achieving required performance is also
discussed. Finally, the roadmap for each technology, as well as the overall program, is presented.
Mach-Zehnder optical modulators were fabricated using the CLD and FTC chromophores in polymer-on-silicon optical
waveguides. Up to 17 months of oven-ageing stability are reported for the poled polymer films. Modulators containing
an FTC-polyimide had the best over all aging performance. To model and extrapolate the ageing data, a relaxation
correlation function attributed to A. K. Jonscher was compared to the well-established stretched exponential correlation
function. Both models gave a good fit to the data. The Jonscher model predicted a slower relaxation rate in the out
years. Analysis showed that collecting data for a longer period relative to the relaxation time was more important for
generating useful predictions than the precision with which individual model parameters could be estimated. Thus from
a practical standpoint, time-temperature superposition must be assumed in order to generate meaningful predictions.
For this purpose, Arrhenius-type expressions were found to relate the model time constants to the ageing temperatures.
A method of chemical synthesis that allows for the facile attachment of a wide variety of chemical compounds, including highly active nonlinear optical chromophores, to polyimides has been developed recently at the Naval Air Warfare Center, Weapons Division. The synthesis of these compounds is presented, along with a discussion of their relevant physical and chemical properties, alone and in comparison to equivalent guest/host materials. Examples of attached chromophores include the well-known Disperse Red 1, along with high-activity chromophores of more recent interest such as FTC and CLD. The synthesis of structures that contain both attached chromophores and chemical functionalities that enable thermal cross-linking of the polyimides is also discussed.
Highly accurate, compact, and low cost inertial measurement units (IMUs) are needed for precision guidance in navigation systems. Active and passive polymer materials have been successfully used in fabricating two of the key guided-wave components, the phase modulator and the optical transceiver, for IMUs based on the interferometric fiber optic gyroscope (IFOG) technology. Advanced hybrid waveguide fabrication processes and novel optical integration techniques have been introduced. Backscatter compensated low loss phase modulators with low half-wave drive voltage (Vπ) have been fabricated with CLD- and FTC- type high performance electro-optic chromophores. A silicon-bench architecture has been used in fabricating high gain low noise transceivers with high optical power while maintaining the spectral quality and long lifetime. Gyro bias stability of less than 0.02 deg/hr has been demonstrated with these components. A review of the novel concepts introduced, fabrication and integration techniques developed and performance achieved are presented.
This is a brief overview of the technology of nonlinear optical polymers (NLOP) and their use in electro-optic (EO) modulators. This paper also covers preliminary results from the authors' laboratories on highly active CLD- and FTC-type chromophores in guest-host films of APC amorphous polycarbonate. Emphasis will be given to thermal stability and long-term EO modulator aging.
The performance of interferometric fiber optical gyroscopes (IFOGs) has continued to advance resulting in expanded applications for both commercial and military inertial sensors. The primary advantages of the IFOG technology for inertial systems are the high reliability and lower cost. Most IFOG designs incorporate a fiber light source, a fiber sensing coil with discrete components connected, typically, with optical fiber pigtails. Fiber light sources require several optical components and are expensive to produce as well as bulky to package. The use of superluminescent diodes (SLDs) as a light source provides a much smaller, less expensive alternative and provides more flexibility in the integration architecture. The challenge for SLD development is the achievement of high power while maintaining the spectral quality and long lifetime. Presented here are the source requirements and the performance achieved for SLD's designed for these applications.
One of the key issues involved in the development of passive optical power limiters is the search for appropriate materials that show effective reverse saturable absorption, Metallophthalocyanines seem to be good candidates for such applications because of their higher optical nonlinearity and the unique electronic absorption characteristics. A series of 1,4,8,11,15,18,22,25-octa-decyloxy metallophthalocyanines containing various central metal atoms such as zinc, copper, palladium, nickel, and cobalt were characterized for their nonlinear absorptive properties to evaluate their suitability to function as reverse saturable absorbers. Nonlinear transmission measurements were analyzed in terms of five-state model and magnitudes of the parameters of the model were determined.
The two dimensional π-conjugated electron system in phthalocyanines allows the tailoring of chemical and physical properties over a very wide range of structural modifications by incorporating many different metal atoms into the ring and by substituting various functional groups at peripheral sites. In this study, a series of
I ,4 ,8, 1 1 ,15,18,22 ,25-octa- butoxy/decyloxy metallophthalocyanines containing various central metal atoms such as zinc, copper, palladium, cobolt and nickel were synthesized. They have significantly altered properties compared to the unsubstituted
phthalocyanines. Spin-coated films of these materials were fabricated and characterized using third harmonic generation process at the wavelength of 1907 nm. The preliminary results of the effects of metal atoms and peripheral substituents on the third order nonlinearity are presented.
The characterization of organic materials for their nonlinear optical properties involves the use of samples in the liquid phase. The most convenient way to prepare samples for such investigations at room temperature is to dissolve the materials in a suitable solvent. However, the influence of the solvent on the measurements
may depend on the physical and chemical properties of both the solvent and the solute. If the solvent effect is not properly taken into account in relating measured macroscopic quantities to the microscopic properties of solute molecules, the comparison of the experimental results of hyperpolarizabilities with the theoretical
predictions may be invalid. In this study, a set of molecules with different sizes of conjugated ir-electron structure designed in a systematic order was used to investigate the structure-property relationship and its dependence on the environment using solvents of varying polarity. The materials used include vanillin Schiff's base
derivatives. Experimental techniques such as electric field induced second harmonic generation, hyper-Rayleigh scattering and solvatochromic method were employed in this study.
Wavelet transform technique is applied to the analysis of data collected in experiments on the characterization of nonlinear optical materials which may be in the form of liquid, thin film or crystal. Many characterization techniques are based on nonlinear optical processes such as higher harmonic generation in which second harmonic or third harmonic signals may be generated by the nonlinear material. When the optical path length of the material is changed, the interference between bound and free waves forms a fringe pattern. Conventional Fourier transform techniques are not suitable for analyzing such fringes when they have a variable periodicity and a low signal-to-noise ratio. However, the wavelet transform method is best suited for such signals because it provides a better resolution in both space and frequency domains. In this study, optical properties of materials are extracted from these fringe patterns by decomposing them into coefficients which are inner products of the signal and a family of wavelets generated from a mother wavelet by dilation and shift operations.
Experimental methods based on nonlinear optical processes such as electrical field induced second harmonic generation and hyper-Rayleigh scattering are often used in measuring the second order microscopic susceptibility of optically nonlinear organic molecules in solution. One of the fundamental problems in these experimental procedures is the influence of the presence of solvent molecules on the optical nonlinearity of solute molecules. We have investigated this solvent effect experimentally and our preliminary results are presented.
The Alliance for Nonlinear Optics is a group of seven faculty at five universities who are working together to develop and test nonlinear optical materials. Each school has its own approach to outreach. In general the group has worked with the academic departments to supplement the departmental efforts. Some of the programs are formal, such as the Visiting Scientist Program at New Mexico Highlands University. Others are informal, such as the faculty efforts to interact informally with the high schools in Puerto Rico. One effort that has been successful is Discovery Day or Science Day, a special day when high school students from around the state are invited to the university for programs in science and engineering. This program has become so popular that it will have to be offered twice this year to meet the demand. Students have been very successful in putting on a chemical magic show in area elementary schools.
The wavelet transform is applied to signal processing of synthetic aperture radar and techniques for determining the range, cross-range, and rotation of the target as well as adaptive process for better resolution are studied. We also optically implement the wavelet transform in the laboratory for real-time processing of radar data, and describe methods for adaptive processing.
The wavelet transform is applied to signal processing of synthetic aperture radar, and techniques for determining the range, cross-range, and rotation of the target are studied. The wavelet transform was also implemented optically in the laboratory for real-time processing of the radar data.
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