We report the results of the first time-resolved observation of impulsively generated coherent optical phonon oscillations in the semiconducting cuprate compound YBa,Cu,O, +x (x < 0.4). The oscillations, which were probed through time-resolved transmissivity modulation, had a period of 237 fs at room temperature, corresponding to a Raman active mode of A ig symmetry at 142 cm-'. No oscillations were observed in the superconducting form of Y-Ba-Cu-0 either above or below T,. The amplitude, frequency, and linewidth of this mode were measured over a temperature range from-7 K to room temperature.

A new method is reported for deflecting a microscopic jet emanating from a nozzle away from the nozzle’s axis of symmetry. It relies on putting energy into the jet through an asymmetric heater embedded in the nozzle. This novel phenomenon is probed theoretically. It is shown that jet deflection is set by the competition among three effects. Two of these can be attributed to the variation with temperature of surface tension and the third to that of viscosity. Whether the contact line is fixed or free is shown to profoundly impact the extent of jet deflection at a given flow rate.

We report the results of femtosecond optical transient absorption experiments performed on the superconducting compounds YBa2Cu307x(X-0) and Bi2Sr2Ca2Cu301O+b(8-0) and nonsuperconducting YBa2Cu306 1-yCy < 0.4) for sample temperatures ranging from

We report the results of Tm3+ doped Ba–Y–Yb–F thin film planar waveguides in glassy form, which produced red, green, blue, and ultraviolet upconverted luminescence when pumped by infrared radiation at λ=960 nm. The films of nominal composition BaYYbF8 doped with 1% Tm have been deposited with both thermal and e-beam evaporation techniques on substrates of fused silica, Si, and GaAs. Planar waveguiding was demonstrated for the films deposited on fused silica. Optimal deposition conditions with respect to the ability of the films to produce upconverted luminescence and low propagation loss are discussed.

We report on a new technique which allows electro-optic sampling to be performed in a frequency range which is above the 1/fnoise regime of the pump-probe laser, while at the same time utilizing the high-sensitivity, low-noise properties of an audio-frequency lock-in amplifier. This new approach to electro-optic signal extraction has resulted in an unprecedented improvement of two orders of magnitude in signal-to-noise capability. The new technique is compared to previous, conventional approaches.

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We report the first measurements of picosecond pulse propagation on transmission lines patterned from YBa2Cu3O7−x films. Distortion-free propagation of high current density transients is demonstrated. The high-frequency properties were analyzed by careful study of the relative phase delays of the electrical transients as the temperature of the sample was varied from 1.8 K to Tc. Simulations using Mattis–Bardeen complex conductivities showed good agreement with the measured results. High-frequency critical current densities in excess of 105 A/cm2 were measured.

An external electro-optic measurement system with subpicosecond resolution has been developed. This electro-optic sampling system is designed to operate as a non-contact probe of voltages in electrical devices and circuits with modified wafer-level test equipment and no special circuit preparation. Measurements demonstrate the system's ability to probe continuous and pulsed signals on microwave integrated circuits on arbitrary substrates with single-micron spatial resolution. We also discuss the application of external electro-optic sampling to various aspects of time-domain circuit studies, including the generation of short electrical test pulses using novel photoconductive techniques and the propagation of pulses on interconnects.