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Full-Text Articles in Engineering
Photographic Studies Of Laser-Induced Bubble Formation In Absorbing Liquids And On Submerged Targets: Implications For Drug Delivery With Microsecond Laser Pulses, Hanqun Shangguan, Lee W. Casperson, Dennis L. Paisley, Scott A. Prahl
Photographic Studies Of Laser-Induced Bubble Formation In Absorbing Liquids And On Submerged Targets: Implications For Drug Delivery With Microsecond Laser Pulses, Hanqun Shangguan, Lee W. Casperson, Dennis L. Paisley, Scott A. Prahl
Electrical and Computer Engineering Faculty Publications and Presentations
Pulsed laser ablation of blood clots in a fluid-filled blood vessel is accompanied by an explosive evaporation process. The resulting vapor bubble rapidly expands and collapses to disrupt the thrombus (blood clot). The hydrodynamic pressures following the bubble expansion and collapse can also be used as a driving force to deliver clot-dissolving agents into thrombus for enhancement of laser thrombolysis. Thus, the laser-induced bubble formation plays an important role in the thrombus removal process. We investigate the effects of boundary configurations and materials on bubble formation with time-resolved flash photography and high-speed photography. Potential applications in drug delivery using microsecond …
Few-Cycle Pulses In Two-Level Media, Lee W. Casperson
Few-Cycle Pulses In Two-Level Media, Lee W. Casperson
Electrical and Computer Engineering Faculty Publications and Presentations
Techniques for producing, measuring, and applying ever shorter electromagnetic pulses are being developed for incorporation in a variety of modern high-speed systems. In many cases these pulses are at most a few cycles in length, and so-called half-cycle electromagnetic pulses are also widely employed. The interaction of such pulses with two-level media is considered here in detail, and these media are basic to many of the absorbing and amplifying configurations of optics and laser studies. Significant delays and distortion of the resulting polarization and population pulses can occur, and nonlinear optical effects are also revealed. The limitations of the parity, …
Spontaneous Coherent Pulsations In Standing-Wave Laser Oscillators: Stability Criteria For Homogeneous Broadening, Pitak Chenkosol, Lee W. Casperson
Spontaneous Coherent Pulsations In Standing-Wave Laser Oscillators: Stability Criteria For Homogeneous Broadening, Pitak Chenkosol, Lee W. Casperson
Electrical and Computer Engineering Faculty Publications and Presentations
The stability criteria for single-mode standing-wave laser oscillators in the homogeneously broadened limit are reported, and two types of criteria are distinguished. The first type (type 1) corresponds to the minimum value of the threshold parameter for which an infinitesimal perturbation away from steady state grows into an oscillatory solution. A second type (type 2) corresponds to the minimum value of threshold parameter for which large-amplitude oscillations do not decay to the steady-state solution. Undamped pulsations in single-mode homogeneously broadened standing-wave laser oscillators are found to occur at a much higher excitation level than in ring-laser oscillators with homogeneous broadening. …
Dynamics Of Ultrashort Pulse Generation And Amplification In Dye Lasers, Shuanghua Jiang
Dynamics Of Ultrashort Pulse Generation And Amplification In Dye Lasers, Shuanghua Jiang
Dissertations and Theses
The dynamics of ultrashort pulse generation and amplification in dye lasers is studied in this dissertation. In particular, we have developed general semiclassical models for ultrashort pulse dye laser amplifiers and oscillators. These models start from Maxwell's equation for the electric field and density matrix equations for the active laser medium. A finite coherence time or phase memory time of the molecular wave functions, a finite vibrational relaxation time for the lower electronic state of the dye laser transition, an isotropic molecular orientational distribution, and an arbitrary pump polarization are all taken into account. Based on these models, specific topics …
Spontaneous Coherent Pulsations In Standing-Wave Laser Oscillators: Simplified Models, Lee W. Casperson, Manuela Fe Tarroja
Spontaneous Coherent Pulsations In Standing-Wave Laser Oscillators: Simplified Models, Lee W. Casperson, Manuela Fe Tarroja
Electrical and Computer Engineering Faculty Publications and Presentations
A series of simplifications and approximations is introduced into a recently described model for spontaneous pulsations in standing-wave laser oscillators. To the extent that these simplifications are valid they can lead to significant reductions in computation time and sometimes also to a better understanding of the relative importance of various physical effects. Of special interest is the number of spatial harmonics required to represent adequately the effects of longitudinal spatial hole burning. Other approximations investigated include neglect of spectral cross relaxation, neglect of multiple-energy-level equations, neglect of electric-field derivatives, and neglect of polarization derivatives. In addition, a detailed discussion is …
Spontaneous Coherent Pulsations In Standing-Wave Laser Oscillators: Frequency Characteristics, Lee W. Casperson
Spontaneous Coherent Pulsations In Standing-Wave Laser Oscillators: Frequency Characteristics, Lee W. Casperson
Electrical and Computer Engineering Faculty Publications and Presentations
The output signal from a spontaneously pulsing laser must, by definition, consist of more than one frequency component. The experimental and theoretical study of the frequency components'associated with such a laser can provide valuable insights into the pulsation processes. The results of an investigation into the frequency characteristics of a spontaneously pulsing standing-wave laser are reported.
Coherence Effects In Synchronously Pumped Mode‐Locked Dye Lasers, Lee W. Casperson
Coherence Effects In Synchronously Pumped Mode‐Locked Dye Lasers, Lee W. Casperson
Electrical and Computer Engineering Faculty Publications and Presentations
A formalism is developed for describing the evolution of picosecond mode‐locked pulses in synchronously pumped dye lasers. The finite phase memory of the molecular wave functions is included, and it is found that the resultant coherence effects can be dominant for operation close to exact synchrony. Considerations of the isotropic molecular orientational distribution and the finite vibrational relaxation times are also essential in obtaining quantitative agreement with experimental results.
Pulse Evolution In Co₂ Lasers, Lee W. Casperson, M. J. Herbst, John J. Turechek
Pulse Evolution In Co₂ Lasers, Lee W. Casperson, M. J. Herbst, John J. Turechek
Electrical and Computer Engineering Faculty Publications and Presentations
Explicit formulas are examined for the development of optical pulses in gain‐switched or Q‐switched laser oscillators and for the distortion of such pulses in succeeding stages of laser amplification. The results are compared to data obtained with a TEA CO₂ oscillator‐amplifier system.
Electromagnetic Modes Of An Inhomogeneous Sphere, Lee W. Casperson
Electromagnetic Modes Of An Inhomogeneous Sphere, Lee W. Casperson
Electrical and Computer Engineering Faculty Publications and Presentations
Vector wave solutions are derived for the electromagnetic modes of a sphere having radial variations of the refractive index and gain. For some inhomogeneity models, confined-mode solutions exist. The results are applicable to the refracting atmospheres of stars and planets.
Output Properties Of Short-Pulse Gain-Switched Lasers, Lee W. Casperson
Output Properties Of Short-Pulse Gain-Switched Lasers, Lee W. Casperson
Electrical and Computer Engineering Faculty Publications and Presentations
A formalism is derived for analyzing the spectral and temporal properties of gain-switched lasers. The development of the longitudinal mode structure from spontaneous emission, limiting linewidths, and over-all spectral characteristics are considered in detail; and applications are discussed.