Joseph Osman

Electro-optic beam-steering device based on a lanthanum-modified lead zirconate titanate ceramic wafer

We demonstrate a lanthanum-modified lead zirconate titanate ceramic-based electro-optic beam-steering device that has a 3 mm × 3 mm working area. A series of resistors were made by evaporation of chromium onto the substrate to produce and control the required voltage distribution among the electrodes. A steering angle of 0.04° was obtained with an applied voltage of 700 V. Design considerations, computer simulations, and experimental results are presented.

Diamond shaped ring laser characterization, package design and performance

A semiconductor diamond-shaped ring laser was fabricated and packaged for further test and analysis as an element in digital photonic logic. The optical characteristics of the ring laser were quantified in order to design a prototype package. The mode field was found to be quasi-circular. Based on the mode field of the laser, coupling curves were calculated and Corning OptiFocustrade lensed fiber was chosen to use for the four fiber outputs. Each fiber placement was actively optimized. Output power measurements were made for each facet before and after fiber coupling. Reflections from fiber tips were found to affect the final output power distribution of the device even though the fibers were anti-reflection (AR) coated, and additional effort was put into minimizing its variance. The packaged devices were tested for performance in digital photonic logic applications. Tests conducted to this point indicate that the packaging enabled a multiple port device of this type to be sufficiently portable for field testing

Nonlinear interface optical switches based on photorefractive thin films

We present the nonlinear interface optical switch in the context of digital optical computing applications. Implications with regard to materials design and development and switch evaluation are discussed. A specific class of materials synthesized using laser chemistry of organometallics is presented. Embodiments of this type of switch have considerable potential for meeting many of the required design criteria for practical implementation of digital optical computing devices.

Evaluation of an extension of a nonlinear interface optical switch structure for dual mode switching

There is a need for devices which will allow integration of photonic/optical computing subsystems into electronic computing architectures. This effort reviews the nonlinear interface optical switch (NIOS) concept and then describes a new effect, the erasable optical memory (EOM) effect. We evaluate an extension of the NIOS device to allow simultaneous optical/electronic, i.e. dual mode, switching of light utilizing the EOM effect. Specific devices involve the fabrication of thin film tungsten (VI) oxide (WO/sub 3/) and tungsten (V) oxide (W/sub 2/O/sub 5/) on the hypotenuse of glass (BK-7), fused silica (SiO/sub 2/) and zinc selenide (ZnSe) right angle prisms. The extent to which the chemical state of the film can also be manipulated electrically, in a purely gas-solid context, is discussed. Temporal response, spatial density of packing the switches and clarifying considerations regarding choices of materials are also presented.

A Surface Raman and Scanning Tunneling Microscopy Study of The Spatial Distribution of Corner-Sharing and Edge-Sharing Octahedra on thermally Oxidized Tungsten

We have measured the dependence of the strength of Raman activity of polycrystalline m-WO 3 on spot size at constant laser power density. These data are compared to surface area scaling measurements obtained using scanning tunneling microscopy. We argue that the spatial distribution of scattering centers is the complement of the spatial distribution of crystallographic shear (CS) structures on or near the oxide surface. Our results are consistent with there being an essentially uniform spatial distribution of scattering sites which implies the spatial distribution of defect sites is also uniform. At the laser power density involved and at the defect densities studied, we found no evidence suggesting a large amount of cooperativity in the formation of CS structures. These results suggest a qualitative description of the structure of common oxide surfaces in agreement with a basic assumption of the JMAK theory of first order phase transformations.

Design of PLZT electro-optic beam-steering device

Quadratic lead lanthanum zirconate titanate (PLZT) is a material demonstrating a strong quadratic electro-optic effect. Both sides of the PLZT wafer were used so that the electro-optic interaction length was equal to the thickness of the PLZT substrate. On-substrate resistive networks were fabricated by evaporating chromium, a less conductive metal, in order to produce the required voltage distribution among the electrodes. The device is polarization insensitive because it takes advantage of the longitudinal electric field. The device yielded a measured steering angle of .04 degree(s). This paper describes the design, fabrication, and experimental results of a PLZT based electro-optic beam steering device.

Ultrafast optical switch evaluation facility

The current major limiting factor in digital optical computing is the absence of a fast, efficient, cascadable optical switch. Material and processing approaches to optical switch construction are not limited to the well known semiconductors and fabrication methods of electronics. A facility to evaluate candidate devices has been constructed. Multiline and tunable femtosecond and picosecond laser systems, as well as frequency mixing systems, are used as light sources. The facility has at least picosecond source capability from 200 nm to 2 micrometers . The switch transfer function is evaluated in a pump-probe system with femtosecond and picosecond autocorrelators to measure temporal properties, an optical multichannel analyzer to measure spectral properties, a CCD or pyroelectric camera system to measure mode modification, and a multi-detector system to measure switching energy and insertion loss both in absorption and in reflection. The switch or switching array under test is mounted in a 6 axis micropositioner system with a 0 - 20 goniometer, x, y, and z translators, and a tilt goniometer. The systems design, as well as initial measurements of nonlinear interface optical switches based on photorefractive thin films are presented.

Reprogrammable digital optical coprocessor

A hybrid electro-optical computer has been constructed. The computer consists of an electronic host computer and a digital optical coprocessor. The optical coprocessor is a free space implementation of an optical programmable logic array. System architecture and fabrication are discussed.