Browsing by Subject "Laser beams"
Now showing 1 - 12 of 12
Results Per Page
Sort Options
Item A study of lasers optically pumped by HF and DF lasers(Texas Tech University, 1978-05) Ross, Randall IrvanNot availableItem An experimental and numerical investigation of laser-plasma interactions(Texas Tech University, 1980-08) Druce, Robert LeeAn experiment to study the interaction of an intense CO2 laser beam with a dense, preformed, magnetically confined, hydrogen plasma has been conducted. Plasma densities considered are on the order of 10^23 m^-3 with initial temperatures of 1-3 eV. The laser is focused into the plasma in the axial direction with the vacuum focal spot positioned at the axial and radial center of the plasma. The results obtained are compared to the results of a computer code developed at Texas Tech University. Mechanisms included in the code are inverse bremsstrahlung heating of the plasma, electron-ion energy equipartition, thermal conduction in electrons and ions, and plasma fluid dynamics. A self-consistent solution of ray tracing in the plasma is also included in the code to predict the self-focusing of the laser beam. Agreement between experimental and theoretical results is generally good.Item Beat heating in plasmas using COb2s lasers(Texas Tech University, 1979-05) Chu, Edmond Y.An experiment using the 10.28 ym and 9.56 ym radiation from a high power CO2 laser and a preionized helium plasma was conducted to investigate anti-parallel beam beat heating. The helium plasma is heated by a focused single, double pass, laser beam with two frequency components. The temperature increase is compared with that obtained using a single frequency laser. A small amount of additional heating is observed with the double frequency laser beam 22 -3 at a spatially average plasma density of 5.3x10 m . However, this additional heating is not as strong as originally expected. The results are explained by the detuning of the beat heating process at the interaction zone due to particle losses.Item Computer simulation of laser-plasma interaction in a magnetic field.(Texas Tech University, 1975-05) Druce, Robert LeeNot availableItem Experimental studies in laser interaction with wavelength scale matter via second harmonic production and hard x-ray production(2006) Sumeruk, Hernan Ariel; Ditmire, Todd R.Item Frequency Domain Holography of laser wakefields(2006) Matlis, Nicholas Hill; Downer, Michael CoffinIn this dissertation, single-shot measurement of longitudinal and transverse structure of resonantly driven laser wakefields by Frequency Domain Holography (FDH) is demonstrated. Visualization of laser wakefield structure is crucial for understanding the complex dynamics of the mutual interaction between the driving pulse, wake- field density oscillations and accelerated electron bunch. This diagnostic therefor provides a necessary tool for researchers to learn how to control and fine tune the interaction to produce electron beams with desirable properties. Wakefields were measured in a 2 mm Helium gas jet, for electron densities between 1 x 1018 and 6 x 1018 cm−3 , and laser pulses of 30 fs duration and peak powers between 10 TW and 30 TW. Detailed structural features of the wakefields, including radial extent of the wake, longitudinal wake development, and wavefront curvature, as well as features of the accompanying ionization front and plasma column are resolved. Results are compared with PIC simulations, and show a high degree of correspondence. Weaknesses of the current implementation of the technique and extensions to other parameter regimes are discussed.Item Interaction of intense laser fields with carbon nanotubes(2006) Hsu, Han; Reichl, L. E.Item Laser chemical vapor deposition of millimeter scale three-dimensional shapes(2001-08) Shaarawi, Mohammed Saad, 1973-; Sanchez, J. M. (Juan M.)Item Laser micro/nano scale processing of glass and silicon(2006) Theppakuttai Komaraswamy, Senthil Prakash; Chen, ShaochenItem Laser micro/nano scale processing of glass and silicon(2006-05) Theppakuttai Komaraswamy, Senthil Prakash, 1977-; Chen, ShaochenThe revolutionary progress in semiconductor, communication, and information industries based on electronic and photonic technologies demands for the development and enhancement of new laser processes to support micro and nanotechnologies. This dissertation is aimed at exploring the use of lasers for micro and nano scale processing of glass and silicon, the most commonly used materials in the IC industry. The objective of the dissertation is two fold: a) use lasers for locally micro bonding glass and silicon wafers, and b) use lasers for nanopatterning glass and silicon substrates by circumventing the diffraction limit of light. In the first part of the thesis, glass and silicon wafers are bonded locally in microscale by a pulsed Nd:YAG laser. Glass is transparent to the wavelength used and hence the laser beam passes through the glass wafer and is absorbed by silicon. As a result, silicon is melted and upon resolidification bonding is realized between the two substrates. The transient melting and resolidification of the substrates is studied experimentally and compared to the simulation results of a finite element numerical model. The bonded areas are studied in detail using a scanning electron microscope and a chemical analysis is done to understand the bonding mechanism. In the second part of the thesis, nanopatterns are created on glass and silicon substrates by circumventing the diffraction limit of light. The nanofeatures are created by irradiating silica and gold nanospheres deposited on a substrate. In case of silica spheres, features approximately half the diameter of the sphere were obtained by utilizing the optical field enhancement around the spheres. In case of gold spheres, features as small as 40 nm were realized by the excitation of coherent resonant electron plasma oscillations. The effect of sphere size, laser wavelength, polarization, incident angle, and energy were studied experimentally. Finally, these experimental results are compared with the numerical results from a multidimensional, heat transfer model.Item Laser triggered spark gap using fiber optic transmission(Texas Tech University, 1981-05) Harjes, Henry CharlesThe use of an optical fiber in a laser triggering system is described. The fiber transmits a high power ruby laser pulse which triggers a high voltage spark gap. The spark gap is a gas switch on a water dielectric Blumlein generator which is pulse charged by a three stage Marx bank. Typical operating parameters for the spark gap are: 2 cm gap, 2700 Torr pressure, Ar-N^ gas mixture, and a charging voltage of 200 kV. The single strand, 1 mm, quartz, optical fiber is selected specifically for high power transmission capability. Laser pulses of 4 MW are coupled into and transmitted by the fiber with no observed damage. The overall optical system transmission efficiency is 62%. The triggering performance of the system is excellent in that switching delays of less than 10 ns and subnanosecond jitters are measured.Item Several new infrared laser pumped lasers(Texas Tech University, 1978-05) Bushnell, Andrew HughNot available