Optical Measurement of Large Sphere Diameters by means of Scattering.

A simple method is demonstrated to determine the diameters of dielectric spheres from 0.2 to 1.0 mm by observing the scattering of visible light. Theoretical calculations show that there is an approximately linear relationship between the size of the scattering sphere and the number of maxima and minima in the scattered field as a function of angle when the radius in the 200-1000-wavelength region.

Active dielectric film laser.

A laser configuration of an optical amplifier that consists of an active dielectric thin film is described. Both the spatial and the temporal mode structure are studied. Analytical and numerical formulations are used to describe the effects of this laser configuration, and experiments are performed to verify the predicted results. It is predicted and observed that the resonator beam width is dominated by the active region width of the film, not by the resonator-mirror curvature.

Measurement of stimulated emission cross section and fluorescence branching ratio for Nd(3+) in sodium-beta'' alumina.

Room-temperature measurements of laser emission cross sections of Nd(3+) ion in sodium-beta" alumina at 1.06 and 1.35 microm as well as the fluorescence branching ratios of (4)F(3/2) to (4)I(j) manifolds are reported. A theoretical calculation based on absolute absorption measurements when a modified Judd-Ofelt phenomenological intensity analysis was used is reported. The cross sections thus determined are sigma(1.06) = 3.1 +/- 0.3 x 10(-20) cm(2) and sigma(1.35) = 0.6 +/- 0.1 x 10(-20) cm(2), respectively. The emission cross section at 1.06 microm was also determined by small-signal-gain measurements and was found to be in good agreement with the above value.

Dielectric film optical amplifier.

An optical amplifier is described using an active dielectric film. Electromagnetic scattering from this type of active film has been studied in the past using infinite plane waves. The use of unbounded fields resulted in scattering coefficients that approached infinity at resonance. In this paper, the active scatterer is viewed as an optical amplifier with finite incident and scattered fields. An analytical description is presented and then supported by a numerical analysis. Finite gains are calculated. This analysis also predicts spatial filtering of the incident field, and experimental results confirm these predictions.

Optical amplification of a multimode evanescently active planar optical waveguide.

The electric field distribution and complex propagation constants of a multimode dielectric optical waveguide with complex index of refraction were calculated. A waveguide with a similar structure was fabricated by ion exchange into a glass substrate. The complex index of refraction region was provided by flowing a dye solution over the waveguide surface. Optical gain as high as 40%/cm was obtained. An experimental determination of the gain of various propagating modes was made and found to be in good agreement with theoretically calculated values.

Phase-matched electromagnetic scattering in active dielectric films.

An investigation of oblique plane-wave electromagnetic scattering from active dielectric films reveals the existence of anomalously large resonances that occur at discrete plane-wave angles of incidence. These resonances may be understood from a leaky-wave phase-matching condition whose predictions for the first few modes agree to within a few percent of those obtained from a rigorous treatment using Maxwell's equations. Enhancement in the scattered-field intensities of the order of 100 was observed in experiments using finite-diameter pump and probe laser beams and active films as thin as 6 microm.

Refractive-index measurements of the beta'' aluminas.

The refractive indices of selected monovalent and divalent beta'' alumina single crystals are determined using prism refraction techniques. The birefringence is found to vary from uniaxial negative to uniaxial positive depending on the electronic polarizability of the exchanged ion. Thus, beta'' alumina is a novel material in which the magnitude and polarity of the birefringence can be tuned simply by ion exchange. The refractive-index data are used to predict an isoindex point (n(e) = n(0)) for the mixed-system Na(+)-Ag(+) beta'' alumina compositions.

Nd(3+) beta'' alumina platelet laser.

Pulsed as well as cw laser action has been observed in a new host material for Nd(3+) ions, Na(+) beta'' alumina. The unusual characteristics of the material and its known physical properties are briefly described. Absorption spectra, fluorescence lifetime, laser-pulse shape, and peak emission wavelength are presented as experimental evidence, and comparisons are made with other Nd(3+) host materials. Some exciting new possibilities for integrated-optics applications are explored.

Multiple angle ellipsometric analysis of surface layers and surface layer contaminants.

A multiple angle ellipsometric method is used for the measurement of substrates covered by contaminant layers and for the measurement of thin film layers on substrates. The method evaluates the fundamental optical constants N and K of the substrate and film layers deposited on it. Results are given for oxided aluminum films on glass, contamination layers on gallium arsenide, silicon oxide layers on silicon, and silicon nitride layers on silicon. This method is applicable to optical and semiconductor substrate and film evaluation, provided the number of layers in the sample is known and the layers are partially transparent.

Light amplification by evanescent wave coupling in a multimode fiber.

Amplification of light propagating as bound modes of a multimode fiber through evanescent wave coupling is reported. Experiments have been performed by immersing sections of a stripped fiber 2-20 cm long in a Kiton red dye solution which is pumped by the evanescent fields of a cw Ar-ion laser also propagating as bound modes of the fiber. Gain coefficients as high as 0.02/cm have been observed by a 633-nm He-Ne probe beam when pumped by a 5-W laser. Numerical calculations obtained by performing a Taylor series expansion of the eigenvalue equation for a cylindrical waveguide with a small active component in the cladding region show that modes near cutoff can exhibit gains 60% or higher, approaching those assumed for the cladding region.

Strain-induced anisotropy measurement in oxide films grown on silicon.

A multiangle single-wavelength ellipsometric method has been applied to the evaluation of anisotropy and stress in SiO(2) films grown on silicon substrate. The method is nondestructive, and it does not require a priori knowledge of the dielectric functions of the oxide layer. A novel theoretical anisotropic multiple-layer program is used to calculate the Fresnel reflection coefficients at various angles of incidence; and an iterative least-squares algorithm compares the theoretical calculations to the experimental data. The data-fitting process yields the index, the thickness, and the anisotropy of the oxide layer and also the index and thickness of the SiO(x) transition layer.

Strain induced anisotropy in As(2)S(3), As(2)Se(3), and ZnSe films on KCI substrates via 10.6-microm and 0.6328-microm ellipsometer measurements and 0.6328-microm reflector measurements.

Ellipsometric measurements at 10.6 microm using a modulated light ellipsometer and ellipsometer and reflectometer measurements at 0.6328 microm are reported for the refractive indices of As(2)S(3), As(2)Se(3), and ZnS films deposited on KCl substrates. The observation of strain-induced anisotropy is reported, and an analysis of the effects of anisotropy in thin film ellipsometry is presented.

Refractive indices of ir materials: 10.6-microm ellipsometer measurements.

10.6-microm ellipsometric measurements, using a modulated light ellipsometer, are reported for the refractive imdies of KCL, CdTe, and ZnSe crystals and for ZnSe and ThF(4) films.

Power dependence of reflectivity of metallic films.

The reflectivity of vacuum-deposited gold films on quartz glass substrates was studied as a function of 10.6-microm radiation power density. A simple linear model of the temperature dependence of the absorptivity of the gold film is developed. This temperature dependence is coupled with a three-dimensional heat flow analysis and fits the experimental data well. The absorptivity alpha is written as alpha(0)(1 + betaT) and the values of alpha(0) and beta are determined, respectively, as (0.88 +/- 0.01) x 10(-2) and 12 x 10(-4)/ degrees C.

CO(2) Laser with Simultaneous Active and Passive Q-Switching.

Experiments were performed on a CO(2) laser using both saturable absorbing gas and slowly rotating mirror Q-switches. It was found that the saturating absorber essentially controls the pulse width and structure over a wide range of mirror rotation rates. A theoretical calculation is also reported. The CO(2) laser and the absorber were both assumed to be two-level systems.

Characteristics of the continuous wave neutral argon laser.

The characteristics of the cw neutral argon ir laser are studied using a variety of techniques. The output power enhancement effects of helium and chlorine gases are measured, and the reasons for the enhancement are determined. The gain is measured for the 2.397-microm, 2.208-microm, 2.062-microm, and 1.792-microm laser lines, using an internal cavity-loss method and a single-pass amplifier method. In addition, the saturation intensity is measured, and competition effects are studied. It is concluded that helium aids excitation of the upper laser levels by producing a significant increase in the electron temperature. Chlorine is shown to aid de-excitation of the lower laser levels by partially depopulating the metastable argon 4s levels that lie just below them.