Control of temporal and spectral jitter in single mode pulsed ND:YAG oscillators

We report reliable operation of a repetitively pulsed (3 pps) passively Q-switched Nd:YAG oscillator on a single longitudinal mode with a high degree of temporal and spectral stability. The total output is 3.5 mJ in a 7-ns bandwidth limited pulse with diffraction limited divergence of 0.33 mrad.     

Coherent Raman gain spectroscopy using CW laser sources

The recent demonstration of stimulated Raman gain (loss) spectroscopy (SRS) using CW laser sources introduces a powerful tool to coherent Raman spectroscopy. In this paper we undertake an experimental and analytical evaluation of several variations of SRS using CW laser sources including (1) direct stimulated Raman gain (loss) measurements, (2) optically heterodyned polarization interferometry, and (3) two-beam nonlinear interferometry. The results show CW SRS to be a convenient and effective means of obtaining direct Raman spectra in applications where background fluorescence precludes the use of conventional Raman techniques. Sensitivities comparable to or exceeding those obtained by coherent anti-Stokes Raman spectroscopy (CARS) are demonstrated. Ultimate sensitivities exceeding those achieved by spontaneous Raman spectroscopy are expected for high-resolution applications in gaseous media.     

Empirical relationships for predicting nonlinear refractive index changes in optical solids

The development of high-power glass lasers has stimulated interest in materials with low index nonlinearity. A number of authors have proposed empirical relations between the nonlinear index and linear dispersion parameters. We review these expressions and relate them to both classical and quantum theoretic derivations of the index nonlinearity. We show that the major differences arise in the treatment of local field corrections. We further show that the good agreement obtained between experiment and theory may be fortuitous, due to the fairly large experimental uncertainty and the fact that all the materials investigated to date are really quite similar, being essentially oxide or fluoride materials.     

Ellipse rotation studies in laser host materials

Using a TEM00qnear Gaussian mode ruby laser system we report the first experimental measurements of intensity induced changes of optical polarization (ellipse rotation) in a cubic crystalline medium, YAG, for which we obtain the nonlinear susceptibilitieschi_{3}^{1221} (- omega, omega, omega, -omega) = 6.34 times 10^{-15}ESU andfrac{1}{2} (chi_{3}^{1111} + chi_{3}^{1221} - 2chi_{3}^{1212}) = 7.18 times 10^{-15}ESU, accurate to better than ±7 percent relative tochi_{3}^{1221} (- omega,omega,omega, -omega)for liquid CS2. These values are compared with further results obtained for fused quartz and two laser glasses. Moreover, by time resolving the ellipse rotation data we demonstrate the capability to plot ellipse rotation versus input power on a single laser shot, thus increasing the practical feasibility of the technique and introducing the possibility of resolving transient contributions to the measurement.     

Comprehensive modeling of diode arrays and broad-area devices withapplications to lateral index tailoring

A numerical model for calculating the emission characteristics of diode laser arrays and broad-area devices operating well above threshold is discussed. This model uses the beam propagation technique for determining the field intensities for several lateral modes, while simultaneously and self-consistently solving for the two-dimensional current flow through the laser structure and the subsequent carrier diffusion in the active region. The active-region temperature distribution is also computed in a self-consistent manner, based on the flow of heat generated in the active region through the layered device structure to a constant-temperature heat sink. The model is applied by investigating the sensitivity of the lasing modes of a broad-area diode laser to variations in the lateral temperature distribution