Bernard Bendow

Optical Properties of Highly Transparent Solids

Section I Multiphonon Absorption.- Theory of Multiphonon Absorption: A Review.- Multiphonon Absorption for Various Forms of the Anharmonic Potential.- Cumulant Methods in the Theory of Multiphonon Absorption.- The High Frequency Tail of the Lattice Absorption Spectra of Simple Crystals.- Optical Absorption by Alkali Halides: Possible Structure in the Multiphonon Region.- Experimental Studies of Multiphonon IR Absorption.- Temperature Dependence of Multiphonon Absorption in Fluorite Crystals.- Multiphonon Absorption in the Alkaline Earth Fluorides.- Multiphonon Absorption in KC?, NAC? and ZnSe.- Two-Phonon Absorption Spectra of III-V Compound Semiconductors.- Section II Electronic Processes.- Urbachs Rule.- Magnetic Circular Dichroism of the Urbach Edge in KI, CdTe and T?C?.- Theory of New Transients and Optical Phenomena in Spatially Dispersive Media.- Dispersion of the Elasto-Optic Constants of Potassium Halides.- Optical Transmission in Iodine Transported ?-HgS.- Section III Impurity Effects.- Impurity Induced Absorption in Transparent Crystals.- Raman, Photoconductive and Acoustoelectric Probes of Residual Deep Impurities and Absorption in GaAs.- Identification of Fe4+, Fe5+ and Fe4+-VO Photochromic Absorption Bands in SrTiO3.- Picosecond Spectroscopy of Transient Absorption in Pure KC?.- Section IV Glasses.- Highly Transparent Glasses.- Multiphonon Absorption in the Chalcogenide Glasses As2S3 and GeS2.- Multiphonon Absorption in Chalcogenide Glasses.- Theory of Multiphonon Absorption in the Transparent Regime of Amorphous Solids.- Light Scattering from Composition Fluctuations in the Superspinodal Region of a Phase-Separating Oxide Glass.- Two-Photon and Two-Step Absorption in Glass Optical Waveguide.- Optically Induced Effects in Photoluminescence Studies of Chalcogenide Glasses.- Section V Multiphoton Processes and Nonlinear Effects.- Nonlinear Spectroscopy in Transparent Crystals.- HF and CO2 Laser Measurements of Dispersion of the Nonlinear Susceptibility in Zinc-Blende Crystals.- Multiphoton Ionization Probability and Nonlinear Absorption of Light by Transparent Solids.- Nonlinear Spectroscopy of Excitons in CuC?.- Nonlinear Wave Propagation in a Transparent Medium.- Picosecond Laser-Induced Damage in Transparent Media.- Second-Harmonic Generation of Intense Laser Light in Transparent Centrosymmetric Solids.- Section VI Measurement Techniques.- A Review of Techniques for Measuring Small Optical Losses in Infrared Transmitting Materials.- Improved Laser Calorimetric Techniques.- Measurement of Small Absorption Coefficients from Thermally Induced Shifts at the Fundamental Edge.- An Alternative Way to Determine Absorption Coefficients in Highly Transparent Solids: Theory.- A Calorimetric Technique for the Measurement of Low Optical Absorption Losses in Bulk Glass and Optical Communication Fibres.- Raman Scattering Technique to Evaluate Losses in GaAs Dielectric Waveguides.- Accurate Spectrophotometer for the Attenuation Measurement of Low-Loss Optical Materials.- Surface Studies with Acoustic Probe Techniques.- A 10.6 Micron Modulated Light Ellipsometer.- Measurements of Stress-Optic Coefficients in the Transparent Regime of Solids.- Measuring Photoelastic and Elastic Constants of Transparent Materials by Application of Static Stress.- List of Contributors.

Vibrational spectra of fluorohafnate glass

Abstract We report the first detailed measurements of fundamental vibrational spectra in fluorohafnate glass. The Raman spectrum is dominated by a single relatively broad peak in the vicinity of 570–590 cm −1 attributed to Hf-F stretching modes, while the infrared spectrum displays two prominent broad peaks. The location of the high frequency peaks is shown to be consistent with the observed position of the infrared absorption edge.

Optics of Thermal Lensing in Solids

The vector Kirchhoff approach to thermal lensing in solids is investigated. The relation of the thermal rise in the sample to the optics of lensing is elucidated. Various analytical results and series representations for the transmitted intensity are derived for the case of Gaussian beams incident on circular samples, in various special limits. An expression for the time-dependent shift in the diffraction focus is obtained. Numerical computations illustrating lensing effects both at small times and in the steady state are presented. Effects of stress-induced birefringence, including the oscillation of the maximum intensity and diffraction focus as a function of time, are illustrated. Similar effects are also shown to occur when the incident power or sample thickness is varied, for solids characterized by large stress-induced contributions.

Optical performance evaluation of infrared transmitting materials

A non-uniform laser beam traversing a material sample undergoes thermal lensing, i.e., distortion and defocusing due to thermally induced changes in refractive index and bulging of sample faces. Vector Kirchhoff diffraction theory is applied to provide a detailed picture of the transmitted beam properties in the presence of lensing. In particular, the time evolution of the focal properties and the intensity degradation are investigated. Four distinct characteristic time regimes are identified for rating solids: ultrasmall, small, transitional and steady-state. The calculations account for birefringence due to thermally-induced stress, which is shown to play a major role in the alkali halides. The optical performance of transmitting materials in various time regimes is evaluated for Gaussian beams incident on thin circular samples. It is found that at 10. 6μm alkali halides, such as KC1 and KBr, substantially outperform semiconductors, such as CdTe and Ge, which in turn outperform various glasses. The relative performance of the alkali halides is found to depend strongly on the incident beamshape, because of stress-induced effects. Detailed quantitative ratings are presented for a wide range of transmitting materials at 10.6μm.

Theory of nonlinear pulse propagation in inhomogeneous waveguides

An approximate treatment of solitons (nonlinear pulses) in inhomogeneous waveguides is presented. We find that, for slowly varying inhomogeneity, both bright and dark solitons are supported by waveguides. These solitons acquire a time-dependent velocity and acceleration but otherwise propagate through the waveguide without changing shape.

Optical properties of infrared transmitting materials

The choice of appropriate infrared transmitting materials for high-power laser applications necessitates a knowledge of various optical parameters. Because experimental data is often scant or unreliable in frequency regions of interest it has become important to be able to predict optical parameters from either theoretical or phenomenological models. This requires identification of the major physical mechanisms, and translation of this information into a useful model. Considerable progress has been made recently, especially with regard to the frequency dependence of refraction, absorption α and photoelasticity. It has been found, for example, that frequency dispersion is important at 10.6μm for all three of the latter quantities in most alkali-halides. For most semiconductors, on the other hand, only the effects on α are significant. It is shown that the mix of existing experimental data with recent theory is now providing us, for the first time, with a fairly comprehensive view of the magnitude, frequency dependence, and temperature dependence of optical parameters of infrared transmitting materials.

Theory of continuous-wave beam propagation in nonlinear optical waveguides

The paraxial approximation is applied to calculate the propagation characteristics of cw beams possessing Gaussian spatial profiles in nonlinear optical waveguides. For powers below the critical power for self-focusing in a homogeneous medium, we find that the waveguide effect dominates, i.e., the beam becomes trapped and the spot size varies sinusoidally. Above the critical power, the propagation is dominated by nonlinearity; the beam becomes unstable and displays self-focusing analogous to that in a homogeneous medium. Mode mixing is defined in terms of the nonlinearity-induced mixing of the initially excited modes at the guide face, and explicit expressions are obtained for the mode mixing for special cases. This mixing vanishes only if the spot size is a constant, a condition that can be satisfied only for special values of the parameters in longitudinally homogeneous, lossless guides.

Theory of thermally-induced interference and lensing in transparent materials

Abstract The vector Kirchhoff approximation is employed to calculate thermally-induced interference and lensing effects on the transmitted intensity, when a laser beam is incident on a thin solid sample with parallel faces.

Prospective Vitreous Materials For Infrared Fiber Optics

Fiber optics operating in the mid-infrared offer the potential for lower losses and better tolerance to nuclear radiation than current silicate-based fibers. Moreover, mid-IR fibers may be useful for a variety of shorter-distance applications such as laser surgery, spot welding and infrared integrated optics. Although a wide array of potentially highly-transmissive mid-IR materials are available in bulk form, most are not suitable for fiber fabrication. Recently, however, a variety of new multicomponent glasses based on the fluorides of heavy metals have been developed, which may offer the best prospects to date for high performance mid-IR fibers. A critical comparison of the advantages as well as the problems associated with various prospective materials and fiber fabrication techniques is given.

Analog image transmission in optical waveguides

We have constructed a refractive index profile confined to a single waveguiding region, which permits analog transmission of one-dimensional spatial images along single optical waveguides.