Laser inhibited diffusion in rhodamine-ethanol solutions

The diffusion of rhodamine-6G dye in ethanol is observed to be inhibited by optical pumping by a cadmium laser. The diffusion process is observed as a function of the solution temperature. The relative difference in diffusion coefficients with and without optical pumping is calculated. The effect is interpreted as being due to a stronger solvent-dye interaction in the first excited singlet state of rhodamine-6G.     

A new method of measuring ultra-short coherent light pulses

A new method of pulse width measurement based on the total energy response of an etalon is presented. The theory is developed and results for several pulse shapes are given. The method is unique because no fast response detector is required and there are practically no spectral region limitations.     

PRESSURE-VELOCITY EQUILIBRIUM HYDRODYNAMIC MODELS

This article describes mathematical models for phase separated mixtures of materials that are in pressure and velocity equilibrium but not necessarily temperature equilibrium. General conditions for constitutive models for such mixtures that exhibit a single mixture sound speed are discussed and specific examples are described.     

External-feedback effects in high-gain scattering media

We report on experimental studies of external-feedback effects on high-gain scattering media. We explain experimental results for the pump energy required for laser action as a function of the separation between a mirror and the media by use of Monte Carlo simulations and integration of the laser equations.     

Theory of laser action in scattering gain media

A laser model based on feedback produced by scattering has been developed to explain the narrow linewidth emission and input-output behavior observed in scattering gain media. The model is based on the transient two-level laser equations and includes the detailed spectral properties of the dye gain system. Monte Carlo methods were employed to calculate the threshold gain required for modeling the input-output and linewidth emission characteristics.     

Spheroidal particle plasmons in amplifying media

The effect of a surrounding gain medium on the localized surface plasmon resonance in spheroidal metal particles is analyzed in the quasi-static limit of the Maxwell equations. It is shown that the gain required to create a singularity in the dynamic polarizability of the particle is significantly lower for non-spherical spheroids than for spheres, and can be as low as several hundred inverse centimeters for noble metals in the near infrared region of the spectrum. Resonant aspect ratios and gain values are calculated as a function of frequency for various metals. The use of non-spherically shaped nano-particles, along with gains achievable in semiconductors and dyes, can result in surface enhanced Raman scattering (SERS) signals which are dramatically enhanced. PACS 61.46.Df; 73.21.Hb; 78.67.Hc     

Self-pulsing and bichromatic emission in homogeneously broadened bidirectional ring lasers

We study the effects of saturation-induced Bragg gratings on the mode structure and dynamics of bidirectional homogeneously broadened ring lasers. The grating is viewed as a distributed feedback medium in a ring cavity and modes appropriate to such a structure are used. A Fourier decomposed rate equation model is developed to study the behavior of these modes above threshold. The difference in the properties of these solutions from the modes of an unfilled ring cavity lead to the possibility of bichromatic emission and both regular undamped and irregular damped self-pulsing.