• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 900
  • 737
  • 287
  • 105
  • 35
  • 35
  • 35
  • 35
  • 33
  • 26
  • 23
  • 12
  • 10
  • 10
  • 8
  • Tagged with
  • 3520
  • 731
  • 633
  • 593
  • 553
  • 533
  • 320
  • 316
  • 311
  • 251
  • 240
  • 183
  • 170
  • 157
  • 154
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
91

Dye laser studies of pulsed high pressure gas discharges

Lawler, James Edward. January 1978 (has links)
Thesis--Wisconsin. / Vita. Includes bibliographical references (leaves 115-118).
92

Laser probing of excited CO products from shock wave initiated oxidation of carbon disulfide

Dibble, Robert W. January 1975 (has links)
Thesis (Ph. D.)--University of Wisconsin--Madison, 1975. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Bibliography: leaves 104-110.
93

Chemical laser studies of elementary chemical reactions

Bittenson, Steven Noel. January 1900 (has links)
Thesis--Wisconsin. / Vita. Includes bibliographical references (leaves 346-352).
94

Polarization effects in photon echoes and in an anisotropic laser cavity.

Kohl, Ronald Harry, January 1972 (has links)
Thesis (Ph. D.)--Ohio State University, 1972. / Includes bibliographical references. Available online via OhioLINK's ETD Center
95

Experimental investigation of laser enhancement of single-bubble sonoluminescence /

Cao, Guohua. January 2005 (has links)
Thesis (Ph.D.)--Brown University, 2005. / Vita. Thesis advisor: Gerald J. Diebold. Includes bibliographical references (leaves 135-139). Also available online.
96

Supermode Si/III-V lasers and circular Bragg lasers

Sun, Xiankai. Yariv, Amnon. Atwater, Harry A. January 1900 (has links)
Thesis (Ph. D.) -- California Institute of Technology, 2010. / Title from home page (viewed 06/21/2010). Advisor and committee chair names found in the thesis' metadata record in the digital repository. Includes bibliographical references.
97

Coupling of a semiconductor laser to a single-mode fiber /

Yu, Nu, January 1987 (has links)
Thesis (M.S.)--Oregon Graduate Center, 1987.
98

Optical and mass spectrometric studies of microwave discharges

Hewitt, Janet A. January 1986 (has links)
The structure, operation and performance characteristics of the TR cell and its role in microwave duplexing in a radar system are discussed. Theory of the microwave discharge is discussed, and the mathematics of microwave transmission along a waveguide examined. Two computer models are established; one to model the transfer of heat from the microwave discharge in the cell to the cell window, and one to model the operation of the TR cell, in terms of the reaction kinetics of the gases within. The results of both models are compared with experimental observations. Finally, the gas in the cell is analysed throughout the manufacturing procedure of the cell and during its operation. Study of the mathematics of microwave transmission along a waveguide leads to expressions for the conductivity, and reflection and transmission coefficients for an ionized gas, resulting in calculations of the electron density in the ionized gas as a function of input power. A computer program to model the heat transfer from the microwave discharge in the TR cell to the cell window has been written. Good agreement with experimental results has been obtained. The temperatures at selected points on the TR cell window, frame and flange are calculated, using the finite difference method. The power incident on the window is input to the program together with the window dimensions and materials selected. The output from the program is in the form of temperatures at selected points across the TR cell window, frame and flange. The temperature at which a window is likely to fail is estimated from the results of the program. Three different techniques are used in the analysis of the gas in the TR cell during its manufacture and operation. They are the study of relative changes in peak heights in the microwave-excited optical emission spectrum of the gas, using an optical spectrum analyser with a recording facility, measurement of the performance of the cell when subject to high power microwave pulses and finally, mass spectrometry of the gases in the cell. Several batches of cells were studied. Using the results from these different analytical techniques, the manufacturing procedure and the operation of the cell are discussed. The batch of cells analysed using mass spectrometry contained traces of oxides of carbon and nitrogen, which were shown to have a negative influence on the performance of the cells. Finally, a computer model of the operation of the TR cell is established. The reaction rates and cross sections of the species likely to be present are calculated from the available literature. The model predicts the number densities of the species present as a function of the operating time of the cell and is used to predict the useful lifetime of the cell. The partial success of the model is due in part to the scarcity of reaction rate data for the microwave discharge.
99

Ultrafast optical nonlinearities in InGaAsP waveguide devices

Roberts, Peter D. January 1996 (has links)
This thesis presents an investigation of the enhanced intensity-dependent refractive nonlinearity in optical amplifiers biased to transparency. Nonlinearities in an optical amplifier with a bulk active region and in optical amplifiers containing four, eight and sixteen quantum wells were compared using picosecond and femtosecond duration pulses generated using colour-centre lasers. Measurements of nonlinear absorptive and refractive dynamics in the amplifiers were performed using pump-probe and time-division interferometry techniques. A curve fitting function was used to distinguish nonlinearities from the measured dynamics. Carrier-heating, caused predominantly by free-carrier absorption, and virtual effects were found to be the most important nonlinearities in optical amplifiers biased to transparency. A strong correlation of the magnitude of the carrier-heating effect with the thickness of the amplifier active regions was observed. A novel measurement of the intensity dependence of the current required to bias optical amplifiers to transparency was performed using a technique which monitored the opto-electronic voltage across the amplifiers. The measurement showed that the transparency current increased linearly with intensity in the 4 QW and 8 QW amplifiers as a result of carrier-heating. Measurements performed on the 16 QW and bulk amplifiers showed a nonlinear variation of transparency current with intensity. These measurements were supplemented with a pump-probe investigation which revealed a negative trend in the transmission with a time constant in excess of 200 ps. It was suggested that a saturation effect related to the amount of heat added to the carrier distribution through free-carrier absorption was responsible for both of these effects. All-optical switching of picosecond pulses via the investigated enhanced nonlinearity was demonstrated in a polarisation switch, constructed using the bulk amplifier, and a nonlinear directional coupler. The optical powers required to perform optical switching were 1.6 W and 5.8 W respectively.
100

Generation and propagation of ultrashort laser pulses using nonlinear waveguides

Su, Zengli January 1995 (has links)
The main objectives in this research project related to the generation of ultrashort laser pulses using a KC1:T1 colour-centre laser and the study of their propagation in optical waveguides. Coupled-cavity mode-locking of the KC1:T1 colour-centre laser using either monomode optical fibre or passive AlGaAs waveguides as the nonlinear element in the control-cavity have been investigated. With the optical fibre as the nonlinear element, pulses as short as 63 fs have been generated. The large nonlinearity of the AlGaAs waveguides illuminated near the half- bandgap energy has been confirmed through the propagation of ultrashort laser pulses, and nonlinear phase shift in excess of 2mu has been observed. By undertaking the studies described here, the measurements have indicated that the waveguides used have a linear loss of 0.74 cm<sup> -1</sup>, a two-photon-absorption coefficient of about 0.1 cm/GW, and a nonlinear refractive index of 0.8 x 10<sup>-13</sup> cm2/W. Coupled-cavity mode-locking with passive AlGaAs waveguides as the control-cavity nonlinear element has been achieved, and two different guiding geometries of the AlGaAs waveguides have been used. With a straight waveguide geometry, pulses having duration of ~ 230 fs have been generated. When a curved waveguide geometry was utilised and appropriate dispersion compensation applied then pulses as short as 160 fs have been produced. By employing waveguides having reduced lengths (down to 1.2 mm), some further shortening of the output pulses was achieved and pulses as short as 150 fs have been recorded. By using a gold coating on rear facet of the waveguide, successful coupled-cavity mode-locking has been achieved at an output power level as low as 4 mW. Some applications using the coupled-cavity mode-locked KC1:T1 colour-centre laser have been performed. Femtosecond pulses at 1.3-mum spectral region have been produced through the process of self-phase-modulation mediated four-wave-mixing in an erbium-doped fibre. Measurement on the group-velocity-dispersion of the AlGaAs waveguide has also been made, and a value of D = -1100 ps/nm/km has been deduced.

Page generated in 0.056 seconds