Engineering Commons^™

Oscillation Frequency In High-Gain Lasers, Lee W. Casperson

Electrical and Computer Engineering Faculty Publications and Presentations

The calculation of the oscillation frequency of a single-mode laser oscillator is examined systematically. Mode-pulling formulas are developed for a variety of laser systems, and the limitations of a standard approximation are explored.

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 …

Pulse-Train Instabilities Of A Synchronously Pumped Mode-Locked Dye Laser: Experimental Phase Plots, Duncan Leo Macfarlane, Lee W. Casperson

Electrical and Computer Engineering Faculty Publications and Presentations

We present experimental phase plots of the pulse-train instability that occurs in synchronously pumped mode-locked dye lasers. From these plots we infer that the instability is of a quasi-periodic, nonlinear dynamical nature. Further, we note that the information lost in this two-dimensional representation is precisely the periodic-versus-erratic character and therefore is of considerable importance.

Effects Of Bandwidth‐Limiting Tuning Elements In Synchronously Pumped Mode‐Locked Lasers, Bahram Zandi, Lee W. Casperson, Duncan Leo Macfarlane

Electrical and Computer Engineering Faculty Publications and Presentations

A description of bandwidth‐limiting tuning filters is introduced into a semiclassical model for synchronously pumped mode‐locked dye lasers. The finite phase memory of the molecular wave functions is included as are the isotropic molecular distribution and the finite vibrational relaxation times. The new set of equations has been solved numerically using the best available values for the various parameters. The results have been compared with experimental data obtained using a rhodamine 6G dye laser, which is synchronously pumped using an acousto‐optically mode‐locked argon laser. Tuning element effects have been studied using two‐ and three‐plate birefringent filters and a tuning wedge, …

Residual Circulation In Shallow Estuaries 1. Highly Stratified, Narrow Estuaries, David A. Jay, J. Dungan Smith

Civil and Environmental Engineering Faculty Publications and Presentations

Long-wave theory and simple turbulence closures have been used to show that three distinct types of circulation (highly stratified, weakly stratified, and partially mixed) arise in narrow, shallow estuaries from the finite amplitude of the tide and the interaction of stratification with vertical mixing. Each type has a different dominant process causing the vertical exchange of salt and fresh water on the flood, and each gives rise to a characteristic residual circulation. The tidal circulation in highly stratified shallow estuaries, described herein, is the result of a finite amplitude internal motion driven by the barotropic tide; shear instabilities at the …

Residual Circulation In Shallow Estuaries 2. Weakly Stratified And Partially Mixed, Narrow Estuaries, David A. Jay, J. Dungan Smith

Civil and Environmental Engineering Faculty Publications and Presentations

Long-wave theory is used herein to analyze circulation in weakly stratified and partially mixed estuaries. Unlike the highly stratified systems considered in part 1, the flows considered here have only a minimal tidal-frequency internal wave component. These estuaries may therefore be modeled as the sum of weakly interacting barotropic and baroclinic modes. The dominant factors driving the residual flow are finite amplitude barotropic effects in weakly stratified estuaries and a combination of barotropic effects and steady horizontal density gradient forcing in partially mixed estuaries. The dominant vertical exchange mechanism in the weakly stratified case is bottom boundary-induced turbulence, and that …

Metamodeling Aspects Of Model Conceptualization, Wayne W. Wakeland

Systems Science Faculty Publications and Presentations

This paper suggests a technique for improving the conceptualization of models. The key aspect of this technique is to set aside the main model for a period of time during the model conceptualization process and focus on building a "watchdog" submodel. The primary purpose of the watchdog submodel is to assure that the main model remains internally consistent during its operation. In the experience of this author, such a submodel can help to identify model conceptualization errors and to determine if a model is sufficiently "robust" to adequately replicate the behavior of the system being modeled.

This is not a …