Integration of silicon nanocrystals and erbium ring cavities for a silicon pumped Er:SiO2 laser.

In this work we present a novel two-stage approach to achieve electrically pumped lasing on a CMOS compatible material platform in the telecom region. The proposed design consists of an electrically pumped silicon nanocrystal (Si-nc) light source acting as an optical pump for an Erbium doped silicate (Er:SiO2) lasing cavity. The integrated design, based on concentric disks of Si-nc and Er:SiO2, provides a means of coupling the Si-nc pump signal to the Er ions without requiring overlap of the Er based lasing mode with the Si-nc material. We present an electromagnetic analysis of the pump and lasing modes in the proposed configuration. We also present fabrication and characterization of Si-nc and Er:SiO2 microdisks as components of the integrated design.

Design and characterization of thin multiple aperture infrared cameras.

We describe a multiple-aperture long-wave infrared camera built on an uncooled microbolometer array with the objective of decreasing camera thickness. The 5 mm thick optical system is an f/1.2 design with a 6.15 mm effective focal length. An integrated image is formed from the subapertures using correlation-based registration and a least gradient reconstruction algorithm. We measure a 131 mK NETD. The system's spatial frequency is analyzed with 4 bar targets. With proper calibration, our multichannel interpolation results recover contrast for targets at frequencies beyond the aliasing limit of the individual subimages.

Electromagnetic analysis of axially symmetric diffractive optical elements illuminated by oblique incident plane waves.

We present an analysis of axially symmetric diffractive optical elements illuminated by off-axis or oblique incident plane waves. The analysis is performed with a finite-difference time-domain method that has been formulated to exploit axial symmetry yet accommodate off-axis illumination. This approach is compared with a full three-dimensional formulation and is found to be more efficient in both memory requirements and computational time. Validation and applications of this method are presented.

Immune-type receptor genes in zebrafish share genetic and functional properties with genes encoded by the mammalian leukocyte receptor cluster.

An extensive, highly diversified multigene family of novel immune-type receptor (nitr) genes has been defined in Danio rerio (zebrafish). The genes are predicted to encode type I transmembrane glycoproteins consisting of extracellular variable (V) and V-like C2 (V/C2) domains, a transmembrane region and a cytoplasmic tail. All of the genes examined encode immunoreceptor tyrosine-based inhibition motifs in the cytoplasmic tail. Radiation hybrid panel mapping and analysis of a deletion mutant line (b240) indicate that a minimum of approximately 40 nitr genes are contiguous in the genome and span approximately 0.6 Mb near the top of zebrafish linkage group 7. One flanking region of the nitr gene complex shares conserved synteny with a region of mouse chromosome 7, which shares conserved synteny with human 19q13.3-q13.4 that encodes the leukocyte receptor cluster. Antibody-induced crosslinking of Nitrs that have been introduced into a human natural killer cell line inhibits the phosphorylation of mitogen-activated protein kinase that is triggered by natural killer-sensitive tumor target cells. Nitrs likely represent intermediates in the evolution of the leukocyte receptor cluster.

Performance of Multilevel Diffractive Lenses as a Function of f-Number.

We study the focusing efficiency of multilevel diffractive lenses as a function of f-number. Both scalar and rigorous analyses are performed on two- and three-dimensional lenses. We show that shadowing in lenses with small f-numbers is a critical factor that limits their performance. We show further that scalar analysis does not accurately predict the effects of shadowing for lenses with long f-numbers and large numbers of phase levels.

Multichannel wavelength division multiplexing with photonic crystals.

A multichannel wavelength-division-multiplexing system consisting of a two-dimensional photonic crystal is proposed. The system consists of two parts, a waveguiding element, realized by defects in a photonic crystal, and frequency-selective elements, realized by photonic crystal microcavities. Simulations, performed with a two-dimensional finite-difference time-domain technique with a perfectly matched layer absorbing boundary condition, showed the ability to filter an incident pulse into six spectral channels with a FWHM of 2 nm.

Photoresist characterization and linearization procedure for the gray-scale fabrication of diffractive optical elements.

We present a procedure for the characterization and the linearization of the photoresist response to UV exposure for application to the gray-scale fabrication of diffractive optical elements. A simple and reliable model is presented as part of the characterization procedure. Application to the fabrication of surface-relief diffractive optical elements is presented, and theoretical predictions are shown to agree well with experiments.

Optical absorption modeling of thermal infrared detectors by use of the finite-difference time-domain method.

The optical absorption of thin-film thermal infrared detectors was calculated as a function of wavelength, pixel size, and area fill factor by use of the finite-difference time-domain (FDTD) method. The results indicate that smaller pixels absorb a significantly higher percentage of incident energy than larger pixels with the same fill factor. A polynomial approximation to the FDTD results was derived for use in system models.

Electromagnetic analysis of axially symmetric diffractive lenses with the method of moments.

We present the electromagnetic analysis of axially symmetric diffractive lenses. Analysis is performed by numerically solving the electric and magnetic field integral equations using the method of moments, and it exploits axial symmetry to reduce computational cost. Formulations for the analysis of loss less dielectric and perfectly conducting lenses are presented. The analysis of binary and eight-level lenses are performed to illustrate the utility of the technique.

Diffractive lens fabricated with binary features less than 60 nm.

We designed, fabricated, and characterized a binary diffractive lens with features less than 60 nm. The lens was designed for operation in the red portion of the spectrum. Experimental measurements of lens performance agree with predictions generated by rigorous models of diffraction.

Electromagnetic optimization of multilevel diffractive elements by use of the wavelet transform.

We present an optimization algorithm for the design of multilevel diffractive optical elements in the electromagnetic domain. The method uses the wavelet transform to parameterize the diffractive optical elements according to a set of coefficients that corresponds to a multiresolution basis. Both local and global optimizations can be performed within a single algorithm. A design example consisting of the optimization of a two-dimensional millimeter-wave diffractive lens over a 10% bandwidth is presented.

Three-dimensional analysis of subwavelength diffractive optical elements with the finite-difference time-domain method.

We present a three-dimensional (3D) analysis of subwavelength diffractive optical elements (DOE's), using the finite-difference time-domain (FDTD) method. To this end we develop and apply efficient 3D FDTD methods that exploit DOE properties, such as symmetry. An axisymmetric method is validated experimentally and is used to validate the more general 3D method. Analyses of subwavelength gratings and lenses, both with and without rotational symmetry, are presented in addition to a 2 x 2 subwavelength focusing array generator.

Field stitching algorithm for the analysis of electrically large diffractive optical elements.

A rigorous electromagnetic algorithm is presented for the analysis of electrically large diffractive optical elements (DOE's), i.e., those that contain small features and have large apertures compared with the wavelength of illumination. The technique uses a finite-sized analysis window within which a rigorous electromagnetic technique is used to solve the local boundary-value problem. To this end the boundary-element and finite-difference time-domain methods are used. The analysis window is translated over the entire surface of the DOE and stitches together the complete solution. We validate the techniques by comparing the stitched boundary fields with those of a complete analysis, in both magnitude and phase, for a binary lens. To illustrate the utility of our method we analyzed an eight-level diffractive lens with a 10, 000-wavelength diameter sampled at 0.05 wavelength that required 8 Mbytes of memory on a desktop personal computer.

Vector-based plane-wave spectrum method for the propagation of cylindrical electromagnetic fields.

We present a vector-based plane-wave spectrum (VPWS) method for efficient propagation of cylindrical electromagnetic fields. In comparison with electromagnetic propagation integrals, the VPWS method significantly reduces time of propagation. Numerical results that illustrate the utility of this method are presented.

Binary subwavelength diffractive-lens design.

We present a procedure for the design of binary diffractive lenses with pulse-width-modulated subwavelength features. The procedure is based on the combination of two approximate theories, effective medium theory and scalar diffraction theory, and accounts for limitations on feature size and etch depth imposed by fabrication. A design example is presented.

Incoherent optical image processing with acousto-optic pupil-plane filtering.

We describe an incoherent image processor that uses orthogonally oriented one-dimensional acoustooptic cells to implement dynamic, arbitrary bipolar point-spread functions (PSF's). Arbitrary PSF's are implemented as a linear superposition in time of separable PSF's. The use of incoherent illumination increases the input field of view over that provided by coherent illumination, and implementation of the PSF by a pupil-plane filter yields a simple, compact single-lens imaging system. The acousto-optic cells offer a faster PSF update rate than that of conventional spatial light modulators, which is a critical issue for the implementation of a bipolar PSF as a subtraction between its positive and rectified negative parts. Initial experimental results are presented that demonstrate the realization of an arbitrary nonseparable PSF, image convolution with a bipolar PSF, two-dimensional image correlation, and an increased processor field of view.

Performance analysis of optical shadow-casting correlators.

We analyze the performance of two optical shadow-casting image correlators that use two-dimensional source arrays to encode the system point-spread function (PSF). The analysis of a standard shadowcasting correlator suggests that the angular divergence of the source array is a critical parameter in the determination of the maximum space-bandwidth product of the image and of the PSF that can be used with such a system. Further, the energy efficiency of a standard shadow-casting correlator is related inversely to the size of the PSF. We show that the constraints on energy efficiency and on the space-bandwidth product of the PSF can be overcome by beam steering the source elements. A modified shadow-casting correlator is proposed that uses phase-only blazed gratings to beam steer the sources. Experimental results generated by a mechanically beam-steered array are presented.

Acousto-optic processing with electronic image feedback for morphological filtering.

An optical morphological processor is described and demonstrated in which the structuring element is generated by means of an acousto-optic cell in the Fourier plane of a coherent optical correlator. A magneto-optic spatial light modulator is employed in the input plane. A single PC generates the drive signals for the acousto-optic cell, processes the output image, and controls the input magneto-optic spatial light modulator. Complex morphological operations of opening and closing are experimentally demonstrated by using electronic image feedback. The results of a morphological noise-removal algorithm implemented by using the optical processor are compared with computer simulations, possible sources of discrepancies are proposed, and potential remedies are discussed.

Crossed Bragg cell implementation of a Fourier-plane filter for optical image correlators.

A two-dimensional optical image processor is described and demonstrated in which the point-spread function is generated by crossed acousto-opticells in the Fourier plane of a coherent optical correlator. Coherence effects and generation of nonseparable point-spread functions are considered.

Effect of food on bioavailability of pseudoephedrine and brompheniramine administered from a gastrointestinal therapeutic system.

The purpose of this study was to determine how a high-fat meal affects the delivery and absorption of pseudoephedrine and brompheniramine maleate when delivered from a gastrointestinal therapeutic system (GITS). This study was a randomized, complete crossover trial with 12 healthy male volunteers who were given single doses of the 24-h GITS under fed and fasted conditions. Pharmacokinetic parameters for both drugs were comparable between fed and fasted treatments, except for a shorter time to maximum concentration of pseudoephedrine for fed subjects (p = 0.002). Bioavailability of pseudoephedrine was 91% for fed relative to fasted treatment; for brompheniramine it was 89%. These results indicate that codelivery of the two drugs from the GITS is reliable and prolonged, and that the resulting absorption of pseudoephedrine and brompheniramine is minimally affected by food.