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This project supplies support for an additional graduate student on experimental investigations on quantum coherence, entanglement, and quantum computation in a solid-state, electronic realization of quantum bits based on superconducting single-electron devices, namely the single Cooper-pair box. Since these qubits can be microfabricated in large numbers on a single chip, addressed and coherently manipulated electronically, and then entangled with each other, they represent one of the most scalable implementations for possible quantum computers. A radio-frequency single electron transistor (RF-SET) is used for readout of the charge state of the qubit. Of particular importance in this scheme is an understanding and the control of the backaction of the measurement system, which can affect the lifetime and coherence of the qubit. Therefore, this backaction is studied with the goal of optimizing the sensitivity and lifetime in order to attain single-shot readout of the qubit., ARO monitor rept. no. 42656-PH-QC.

Liquid microdroplets play an important role in combustion as well as atmospheric chemistry. Characterizing droplets in terms of size, shape, chemical composition, temperature, etc., is essential for research in these two fields. Nonlinear optics has proven to be a useful diagnostic tool for determining these important characteristics. The research funded by this contract has resulted in the development of three new diagnostic techniques for characterizing microdroplets with mode locked laser pulses: (1) The temporal beating of adjacent, degeneracy split droplet cavity modes has been used to determine both the droplet distortion amplitude and the linewidths of the cavity resonances. (2) The localized, laser induced electrostrictive distortion induced by a train of mode locked laser pulses was shown to increase the input coupling to droplet cavity resonances for subsequent laser pulses and reduce the threshold for stimulated Raman scattering by almost two orders of magnitude. (3) Optical second harmonic generation has been used to both detect surfactant molecules adsorbed on droplet surfaces, as well as to determine the relative concentrations and molecular orientations of the surfactants.

Significant progress has been made in the following two research areas: (1) Nonlinear spectroscopy of micrometer-sized multicomponent droplets; and (2) Two- and three-dimensional scalar and velocity mapping. Optical diagnostics that have the potential of providing information on chemical species and temperature of multicomponent liquid droplets have been developed. A brief summary of the research accomplishments in the following three areas: (1) droplet temperature determination with thermochromic dyes; (2) enhancement of stimulated Raman scattering from droplets for identifying chemical species; and (3) modification of droplet lasing characteristics by injection seeding and Q-switching. Progress has been made in developing and applying a technique for obtaining mixture fraction and scalar dissipation in a variety of turbulent nonpremixed flames. The data from these experiments are of use for modeling these complex systems. In premixed flames, simultaneous velocity/scalar images were obtained, along with full three-dimensional gradient and OH information.

We summarize the new accomplishments that were made possible as a result of the acquisition of two CCD detectors (one gateable CCD detector and one liquid nitrogen cooled CCD detector, both from Princeton Instruments) with one common controller. Progress has been made jointly with Drs. Ronald Pinnick and Steven Hill (of the Army Research Laboratory, WSMR, NM) mainly in the area of fluorescence-spectra determination of single biological airborne particle as the particle flew by the pulsed UV laser focal volume. By using the gateable CCD detector, we have demonstrated the ability to capture the fluorescence spectrum on one type of particle while ignoring others. The decision as to what type of particles to capture the fluorescence spectrum is solely based on the particle fluorescence and/or elastic scattering characteristics. By using the liquid nitrogen cooled CCD detector, we were able to determine, with several UV laser wavelengths (266 nm and 355 nm), the fluorescence spectra of a large number of biological particles in various environments, i.e., whether the biological spores on a glass slide are dry or in an optical cell containing water. Spectral shifts and changes in the fluorescence intensity are noted. The usage of these DURIP-Yale instruments in other DoD sponsored research topics are briefly mentioned.

Review is made of the feedback and gain enhancement mechanisms unique to microdroplets. In particular, the growth of stimulated Raman scattering is considered in the presence of two-photon absorption as well as the usual optical losses inside the droplet because of scattering and leakage out of the droplet cavity.... Microparticles, stimulated Raman scattering, stimulated Brillouin scattering, and two-photon absorption.

Significant progress has been made in the following areas: (1) Nonlinear spectroscopy of micrometer sized droplets, and (2) Development and application of two- and three-dimensional scalar and velocity measurement techniques in flames. In the nonlinear spectroscopy area, the following achievements are reported: (1) Fluorescence seeding of the stimulated Raman scattering (SRS) in order to increase the detectivity (by as much as 10X) of minor species in a multicomponent liquid droplet that contains a fluorescent dye; (2) Temporal precession of the SRS as a means of determining the shape distortion (7 parts out of 10(exp 3)) of a flowing droplet because of inertial force; (3) Preliminary measurements of the relative evaporation rates of 15 droplets in a segmented stream where the few lead droplets evaporate faster than the remaining droplets; and (4) Suppression of lasing by the SRS and amplification of the SRS in microdroplets, leading to an increased SRS signal. . .. Droplets, Spray, Evaporation rate, Shape distortion, Precession of cavity modes and Lasing, Premixed flames, Nonpremixed flames, Rayleigh scattering, Laser-induced fluorescences, Three-dimensional measurements, Laser diagnostics, Flow imaging, Supersonic flow, Mixture fraction and Scalar dissipation.

Recently, electron-hole transport in photorefractive media has received much interest. Many observations which cannot be accounted for by simple single-carrier single-level transport can be explained by electron-hole transport. This summary describes electron-hole transport by two different models and describes a regime in which both models give similar results. For the single-level electron-hole-transport model considered, one species of traps exists in the band gap, and charge transfer occurs by both electron and hole transport. For the two-level electron-hole-transport model, two species of traps exist in the band gap, and charge transfer occurs by electron transport for the species closest to the conduction band and by hole transport for the species closest to the valence band. For most regimes, the two models give significantly different results. Saturation space-charge fields depend on the model used; for the single-level model, the field depends on the relevant rate constants, but for the two-level model, it depends on the relevant limiting space-charge fields. The number of time constants depends on the model used; the single-level model yields one time constant, whereas the two-level model yields two. And only the two-level electron-hole-transport model allows the presence of complementary gratings., This article is from 'Organization of the Optical Society of America Photonic Science Topical Meeting Series. Volume 14. Photorefractive Materials, Effects, and Devices Held in Beverly, Massachusetts on 29-31 July 1991,' AD-A253 001, p345-348.

The combustion of liquid propellant spray offers new challenges for optical diagnostics. During the four years of ARO support, we have attempted to apply nonlinear optical spectroscopy as an in-situ probe to the determination of the chemical composition in the droplet and the droplet size. Droplets of low molarity ammonium nitrate in water are used as test samples. The SRS spectra of such droplets consist of two peaks at the vibrational-shifted frequencies of the nitrate ions and of the water molecules. The frequency shifts of the simulated Raman scattering (SRS) from the input laser frequency are equal to the vibrational frequencies. The dominant SRS peaks associated with the nitrate ions and water molecules are noted to consist of a series of equally spaced peaks which are attributed to morphology-dependent resonances of a droplet. The droplet radius can be accurately deduced from the wavelength spacing of the series of SRS peaks. The SRS intensity ratio of the nitrate peak and the water peak is proportional to the logarithmic ratio of the nitrate concentration and water concentration. The incident laser and SRS intensities inside the droplets are high enough to produce third order sum frequency generation and two-photon absorption.

The collaboration between Yale and the Westinghouse Science and Technology Center produced high quality, sub-micron, superconducting Nb trilayer tunnel junctions. These junctions were made using a fabrication process developed at Westinghouse as a result of this collaboration. The junctions were fabricated on thin (2 mil) quartz substrates using the existing facilities at Westinghouse. The quality of these devices compares favorably with others reported, particularly in the sub-micron size range. These junction were used as receiving elements in a broad-band 80-120 GHz mixer receiver. This receiver had no mechanical tuning elements. The noise of this receiver using these devices is among the lowest reported in the 80-120 GHz frequency band, particularly among those with no mechanical tuning elements.

During the three years of ARO support, significant progress has been made toward furthering the understanding of high-intensity laser beam interactions with single liquid droplets with radius, a, much larger than the input laser wavelength (input). Our research efforts can be divided into two parts: (1) laser-induced breakdown (LIB) of droplets; and (2) nonlinear optical effects in droplets. One part of our research was directed toward the optical diagnostics of the plasma associated with the laser-induced breakdown (LIB) processes. We developed several spectroscopic techniques that are capable of providing spatially and temporally resolved measurements of the plasma emission and transmission. The propagation speed and the optical transmission of the breakout plasma from the droplet shadow face and from the illuminated face are determined. The relative heating of the atoms in the plasma is extracted from atomic emission intensities at two different wavelengths. The other part of our research was directed toward the following nonlinear optical effects: (1) the generation of stimulated Brillouin scattering (SBS) in simple droplets; (2) the determination of the angular pattern of stimulated Raman scattering (SRS); (3) the two-photon excitation of lasing droplets; and (4) the modification of the standard nonlinear wave equations to describe the growth and decay of nonlinear waves in droplets.

Research was conducted on deposition and characterization of high temperature superconductor films. A number of configurations for sputter deposition of films were tested, including three-source co-sputtering with the guns facing, and with the guns off-axis, from the growing film, and single composite-target sputtering. The best film properties were obtained with off- axis, single target sputtering onto a heated substrate. Films were deposited onto heated magnesium oxide substrates using simultaneous sputtering (co- sputtering) from three metal targets: yttrium, copper, and a barium copper alloy. After a significant number of depositions were carried out to optimize film composition and to maximize transition temperature, we began deposition onto substrates of strontium titanate. These substrates allowed higher transition temperatures and films with lower resistivities.

The major progress in the first year of AROSR support has been made in the area of laser interaction with micron-size droplets flowing in a linear stream. Motivated by our interest in finding bright fluorescent markers for LDV instruments, we have continued the study of lasing droplets. Magnified photographs of lasing droplets reveal that the laser radiation is confined just within the liquid-air interface, whether the actual droplet shape is spherical or spheroidal. The possibility of providing chemical species identification of liquid droplets from the nonlinear optical spectra of droplets led us to investigate the stimulated Raman scattering, coherent anti-stokes Raman scattering, and coherent Raman mixing processes within the droplets. Progress in these areas is described. Considerable effort was devoted to developing an optical technique which has the potential of providing three-component velocity mapping in three dimensions. Double-pulse holographic experiments are currently under way with seeded particles in a cold flow. the observed particle tracks are being analyzed by a novel application of the Hough transform which is well known in the pattern recognition field. Progress in this area is also discussed.

Consider high intensity laser beam interactions with single transparent micrometer size droplets flowing in the linear stream applied to real time diagnostics of the chemical species contained within droplets of sprays. Research efforts are directed toward exploring the limits of high intensity irradiation of micrometer size transparent droplets. Two effects are considered: (1) the intensity dependent index of refraction of the liquid, which can lead to self focusing of the laser beam within the droplet and to broadening of the Raman radiation and elastic scattering due to phase modulation within the droplet; and (2) laser induced dielectric breakdown, which can occur either in the gas surrounding the droplet or in the liquid within the droplet. The breakdown generates a shock wave and/or an optical detonation wave which causes material to stream from the droplet and form plumes. Success was achieved in developing an optical technique with potential of proving three component velocity mapping in three dimensions. A time coded five pulse volume holography of silver coated hollow spheres seeded in a cold flow has been recorded, and an automated pattern recognition technique (Hough transform) has been adapted to identify straight lines formed by the five exposures of the same silver coated particles, which were sparsely seeded in a nozzle flow.

All items of equipment were purchased during the period August, 1984 to August 1985. In August, 1985, the Principal Investigator, M. Krishana, left Yale University for Physics International Co. (PI). At PI, he is pursuing pulsed power driven x-ray lasers. The equipment acquired at Yale remains uncrated and unused, because of the departure of M. Krishnan and because of the termination of the research Grant (81-0077) on January 31st, 1986.

In n-channel silicon inversion layer the small resistance changes with temperature below 4K have been observed and the physical mechanisms quantified. These mechanisms are a temperature dependent elastic scattering which is mostly mitigated by impurities, and the many body effect upon the elastic scattering. In high quality silicon MOSFETs, inelastic diffusion lengths of about 2 micrometers have been observed, which demonstrated quasione dimensional transport processes in submicron devices. Keywords: silicon inversion layers; elastic scattering; inelastic scattering; submicron devices; Metal oxide semiconductors; Field effect transistors.

This project deals with electron impact experiments on atoms and molecules relevant to the development of the N2-CO2 and rare-gas halide lasers. Cross sections for state-of-state transitions in a variety of collisional processes (rotational, vibrational, and electronic excitation; dissociative attachment) have been determined in the first 4 eV of threshold and are generally found to exhibit great enhancement attributable to resonances. Highlights of the methods of cross-section measurement are also presented.