United States of America As Represented by the Secretary of the Air Force

University of Louisville Research Foundation, Inc.

Other

Robert W Cohn

Mehdi M Yazdanpanah

Gamini U Sumanasekera

Romaneh Jalilian

Anton N Sidorov

P John Ouseph

Vladimir Dobrokhotov

Steven A Harfenist

Abdelilah Safir

Frank P Zamborini

Brigitte H Fasciotto

Mahdi Hosseini

Shaad Bidiwala

Santosh Pabba

Minhua Liang

The invention provides method for metallic nanonstructures self-assembly methods and materials testing. Preferred embodiment methods permit for the formation of individual nanostructures and arrays of nanostructures. The nanostructures formed can have a metal alloy crystal structure. Example structures include slender wires, rectangular bars, or plate-like structures. Tips can be shaped, single layer and multiple layer coatings can be formed, tips can be functionalized, molecules can be adhered, and many testing methods are enabled.

Metallic nanostructures self-assembly, and testing methods

A method for electrostatic deposition of graphene on a substrate comprises the steps of securing a graphite sample to a first electrode; electrically connecting the first electrode to a positive terminal of a power source; electrically connecting a second electrode to a ground terminal of the power source; placing the substrate over the second electrode; and using the power source to apply a voltage, such that graphene is removed from the graphite sample and deposited on the substrate.

Method for electrostatic deposition of graphene on a substrate

The placement accuracy and resolution of direct-write patterning tools, in particular the atomic force microscope (AFM), is considered for application to fabricating multi-passband integrated optical filters. Because of its simpler fabrication a grating structure is proposed that consists of identical stripes that are non-periodically spaced. The recently developed pseudorandom encoding method from the field of computer generated holography is modified to effectively assign analog reflectances at each point along the grating by selective withdrawal and offsetting of the stripes from a periodic spacing. An example filter designed by this method has two 1.5 nm bandwidth passbands and &minus;23 dB of rejection for lightly coupled stripes. As with single band filters, the passbands broaden as the coupling increases. A calculation of the coupling coefficient of stripes on a fundamental mode, slab waveguide indicate that stripes on the order of 100 nm in depth and width support low insertion loss, multipassband filtering applications at visible wavelengths. Lines of these dimensions patterned with an AFM on (110) silicon indicate the feasibility of fabricating these filters. These conclusions are specific to current AFMs that are limited to writing fields of 100 &mgr;m. Increased rejection and decreased passband widths will result from incorporating precise field-stitching into future AFMs.

Nanolithography for multi-passband grating filters

Two pixel-oriented methods for designing Fourier transform holograms, pseudorandom encoding and minimum distance encoding when combined usually produce higher fidelity reconstructions than either method produces individually. In previous studies, minimum distance encoding was defined as the mapping from the desired complex value to the closest value produced by the modulator. This method is compared with a new minimum distance criterion in which the desired complex value is mapped to the closest value that can be realized by pseudorandom encoding. Simulations and experimental measurements using quantized phase and amplitude modulators show that the modified approach to blended encoding produces more faithful reconstructions than the previous method.

Modified minimum distance criterion for blended random and nonrandom encoding

Spatial light modulators (SLMs) can be amplitude-only modulated, phase-only modulated, or the pixel amplitudes can even be a function of phase. However, practical devices providing independently controllable values of phase and amplitude are not expected for some time. It has been possible to design modulation patterns for these limited range SLMs that do produce diffraction patterns similar to those possible from full complex SLMs, but hours of intensive iterative optimization usually have been required. Our approach instead develops and evaluates direct, pixel-by-pixel encoding algorithms that map the limited range modulation properties onto the entire complex plane. The advantage of these algorithms (generally recognized by the name pseudo random encoding) over iterative optimization is that designs can be performed in real-time making systems adaptable to rapidly changing situations. For laser scanning using SLMs, encoding enables multiple spots to be generated and their positions to be maintained on multiple moving targets. For correlators, a fast encoding method would provide a way to adaptively construct composite filters (capable of recognizing objects from many perspectives, or classes of objects) by linearly combining individual matched filters. For fixed pattern diffractive optical interconnects, the encoding method can lead to faster iterative optimization algorithms, as well and the devices that are suggested by the design can be affordably produced using existing microfabrication art.

Extensions and improvements of method of producing an optical wave with a predetermined function

A five step method is used to produce an optical wave. The first step is to pick the desired far field pattern of the diffractive optical wave. The second step entails transforming the desired far field pattern to the desired source using a fast fourier transform (FFT). In the third step we use the formula exp[j.phi..sub.i (.sigma..sub.i)]=A.sub.i exp(j.phi..sub.i) to find the standard deviation .sigma..sub.i for each pixel i that produces the desired/average amplitude. Next, we use a pseudo-random number generator to select phases .phi..sub.i from distributions of standard deviation .sigma..sub.i for each pixel. Finally, we check the solution with the FFT and our analyses of performance.

Method of producing an optical wave with a predetermined optical function

A video-rate correlator constructed with a phase-only spatial light modulator and video camera. The phases of the Fourier spectra of a test and reference image are measured by real-time fringe scanning interferometry. The two phase images are then electronically subtracted. The optical Fourier transform of this difference produces the phase-only correlation response. This correlator is real-time adaptive, in that it uses live imagery, and neither the test or reference images need any preprocessing off-line. Especially small optical layouts, which also efficiently use light for correlation, can be configured through the use of specific embodiments, which use only a single phase-only spatial light modulator and Fourier transform lens.

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Louisville, KY, United States of America

Robert W Cohn