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The Bloch wave formalism is employed to explain the asymmetry of the spectral response of various distributed-feedback lasers with respect to the gap by terminating the laser facets judicially. The analysis proves that the phase and amplitude of the reflection coefficient for Bloch waves are extremely helpful in determining the spectral characteristics of such distributed-feedback lasers.

Various studies are conducted to analyze carrier illumination (CI), a photoelectrothermal modulated optical reflectance (PMOR) technique that is used for one dimensional active doping profile characterization of ultrashallow junctions. The described method makes use of the power curve's first derivative at low, as well as high illumination powers, but is still not very reliable, as it has a limited extraction range.

A systematic study of the effect of phosphorus passivation on surface Fermi pinning by using photoreflectance spectroscopy (PR) is presented. A maximum reduction of the Fermi level using epitaxially grown GaP with an effective coverage of two monolayers is observed.

Franz-Keldysh oscillations of piezoreflectance in a delta-doped gallium arsenide were studied through the application of fast Fourier transformations. The piezoreflectance of Franz-Keldysh oscillations and their fast Fourier transformations spectra were described by a model calculation which includes the energy gap modulation in a uniform electric field. Results revealed that Franz-Keldysh oscillations line shapes in the piezoreflectance had no distortions of the modulation electric field similar to the experiments about photoreflectance and electroreflectance.

A study was conducted to analyze the optical properties of zirconium selenium which was grown on a gallium arsenide substrates through the use of contactless electroreflectance, piezoreflectance, photoreflectance and photoluminescene. The contactless eletroreflectance and piezoreflectance spectra were compared. Results revealed that optical properties of zirconium selenium grown on gallium arsenide can be accurately examined the spectra of the given methods.

Theoretical analysis of the impact of structural and doping nonuniformities on the reflectivity spectrum of AlGaAs distributed Bragg reflector shows that p-type doping affects the reflectivity spectrum while arbitrary variations in thickness do not exert any major influence on the spectrum. Changes in composition and mirror structure affect the spectrum, showing that the inclusion of doping effects in mirror design is important. Analytical studies help determine the effect of changes in refractive index on the reflectivity spectrum.

Analysis of the influence of back surface reflectance (BSR) on the photoreflectance (PR) spectra of semi-insulating GaAs reveals that the peak amplitude of below-gap structures of BSR depends on temperature in the 78 to 290 K range, while at low temperatures two spectra of distinct physical origin superimpose. The long-wavelength absorption tail of excitons induce a fast component in the PR spectra at low temperatures and during electric field application. However, the slow spectral component is more predominant at room temperature and originates from the Franz-Keldysh electroabsorption process.

Auger depth profiling, transmission electron microscopy, X-ray diffraction and Rutherford backscattering spectroscopies of UHV evaporated and sputtered Si/Mo multilayer mirrors reveal the presence of thin amorphous alloy interlayers between the Si/Mo layers. Surface contamination and multilayer structure influence the extreme ultraviolet sensitivity of the mirrors. Peak reflectivity of normal incidence mirrors is 33% and that of 45 degrees mirror is 53% at 23.6 nm and 18.6 nm, respectively.

Infrared reflectivity of A(B'B')O3 perovskite ceramics indicates that the development of an additional vibration mode correlates with the degree of B-site ordering. X-ray diffraction and transmission electron microscopy reveal strong maxima and weak reflections in certain ceramics. The short-range ordering sensitivity of infrared reflectivity indicates that the extra mode develops despite low ordered material volume in the ceramics.

Time-resolved reflectivity suggests a melting model for the pulsed laser melting process of Si substrates implanted with 74Ge+ ions. Two reflectivity peaks seen in Ge-implanted samples are explained assuming that an inhomogeneous melting process occurs in Ge-implanted samples during laser irradiation. The liquid phase nucleates below the sample surface due to melting temperature decrease caused by the Gaussian Ge-implantation profile. The two reflectivity peaks form from a time regulation of the liquid-solid ratio at the sample surface.

The presence of transverse electric modes in Bragg optical fibers reduces losses and depends on the reflectivity and phase condition of the fibers. The optical fibers contain a cylindrical Bragg grating that prevents radial power flow. These optical fibers are efficient single-moded structures that do not induce a degenerative polarization effect.

A new method determined the characteristics of reflected and refracted waves, resulting from the collision between a spherical wave and a planar interface that divided two elastic solids. The reflection and refraction coefficients were sensitive to the wavefront curvature, source frequency and interface boundary conditions. Reflected waves caused fragmentation in specific materials even when the two solids exhibited an excellent impedance match.

Soft X-ray radiations are employed to measure the reflectivity of a W-C multilayer structure embedded in a silicon substrate heated with the help of a seven-nanosecond Nd-YAG lazer pulses. Laser heating increases the reflectivity and the spacing of the layers. Melting of tungsten layers increases the smoothness and the reflectivity.

The strain field, with respect to defects, did not influence the degree of network strain in amorphous silicon (a-Si) which contained a continuous random network that was covalently bonded. Subpicosecond resolution, which employed pump-probe reflectivity measurements, was used to study a-Si defects.

Photoreflectance and photoluminescence analyses facilitate the determination of the optical properties of CuInS2 and the comparison of the structural properties derived by energy dispersive X-ray microprobe analysis and X-ray diffraction. Transitions in the photoreflectance spectra are due to Wannier excitons. Field-induced change of the excitonic dielectric function explains these transition. Small inhomogeneities in the molecularity of the compound do not affect photoluminescence.

Polarized neutron reflectivity analysis of the spin structure of antiferromagnetic Fe/Cr layers reveals that their magnetic domains were laterally limited, with no correlation between the domain size and magnetoresistance. The results imply that magnetoresistance originates at microscopic levels in interface imperfections.

Total reflectance of polycrystalline SILSO silicon wafers with a mechanically grooved surface is investigated between 300 and 1500 nanometers. The optical path length in the 1100-1200 nanometer range for a 35 degrees V-grooved surface and a nonmetallized backside is 33 times higher than that of a nongrooved wafer. Deviations from ideal geometry of the grooved surfaces leads to an enhancement in reflectance.

Davydov solitons are identified using the pump-and-probe method of transient reflectivity (TR). Solitons can be generated by direct stimulation with infrared radiation since bond energy is the only criterion for soliton formation. TR can eliminate chromaphores and appearance of sinusoidal TR signal only with solitonic motion.

A simple and ultrasensitive optical method, based on differential reflectance (DR), is used for determining damage profiles in semiconductors. In inert gas and reactive ion etched GaAs and in GaAs implanted by Ar and He, the depth distribution of damage is determined. Mass of the ions used in the etching procedure is inversely proportional to the damage due to sputter etching.

The subpicosecond time- and spectral-resolved transmittance and reflectance characteristics of hydrogenated amorphous silicon (a-Si:H) films are studied. Experiments are conducted wherein a a-Si:H film is subjected to amplified laser pulses with a spectrum of 625 nanometers. The time-resolved transmission and reflectance measurements are obtained by means of differential transmission and differential reflectance spectroscopy methods. Results reveal the presence of several relaxation mechanisms that affect the temporal evolution of the a-Si:H film's optical response.

The in-plane optical anisotropy (IPOA) of asymmetric (001) GaAs/AlGaAs quantum wells (QWs) is investigated, where the asymmetry is introduced via the insertion of a monolayer of InAs or AlAs at the interfaces of the QWs. The results show that the insertion of monolayer material at interfaces provides a convenient way to control IPOA in (001) QWs.

A Crystalox MLGS-3 system helps the fabrication of (K(0.5)Na(0.5))0.2(Sr(0.75)Ba(0.25)0.9Nb2O6 photorefractive crystals with enhanced photorefractive property due to Mn doping. Experimental studies of these crystals indicate the self-pumped phase conjugation reflectivity to be more than 40% and the two-wave coupling gain to be 37.60 per cm. The phase conjugation reflectivity varies with incident power and incident angle.

Optical band-gap narrowing, detected in transparent and conducting ZnO thin polycrystalline films developed using the Pyrosol process, occurs when the carrier concentrations correspond to metal semiconductor transition. A model developed for Si:B and Si:As layers supports the carrier concentration-dependence of band gap-shrinkage. Double-beam spectrophotometers help measure the films' reflectivity and transmission spectra.

Photoreflectance and photoluminescence studies of molecular beam epitaxially developed GaAs layers reveal that sulfur treatment results in a 15-fold increase in the intensity of the layer. Sulfur treatment in As-developed GaAs layers eliminates the spectral peaks. Sulfur passivates the nonradiative recombination centers and induces chemical absorption in the GaAs layers.

Reflectivity calculations of the backsurface of thin polyimide films reveal a temporary reduction in reflectivity during ArF excimer laser ablation. The reduction strengthens on ablative fluence increase. The effects of ablation plume and surface mechanisms are removed on backsurface reflectivity observation. This reflectivity reduction results from temporary changes in the optical properties within the solid polymer material during ultraviolet laser ablation.

Appropriate surface treatment and dispersed polymers control the bistability and reflectivity of display from cholesteric liquid crystals. Polymer dispersion in these liquid crystals makes permanent defects, which increase the bistability and contrast, and exhibit a wider viewing angle. These crystals, at room-lit conditions, exhibit a bright color without polarizers. These crystals are used in displays for computers and electronic books.

Simulation of interdiffusion of Ga and Al at interfaces bound inside the GaAs/(Al, Ga)As-distributed Bragg reflectors (DBR) are used to analyze the changes in stopband width, penetration depth and reflectivity of disordered DBRs. The analysis reveals that short diffusion lengths have no effect on optical parameters. Long diffusion lengths considerably reduce parametric values.

The utilization of real time reflectivity measurements at the HeNe laser wavlength in the characterization of solid-liquid transition induced in antimony at 193 nm by pulsed laser irradiation is discussed. Reflectivity transients at energy densities above the melting threshold were analyzed. It was found that the melting for energy densities below 150 mJ cm-2 proceeds inhomogenously.

The thermal stability in vacuum of Cr/Sc multilayer thin films used as reflective optical components in soft x-ray instrumental has substantial dependence on incorporation of N. The studies have shown that the separation into the different multilayer periods is a consequence of redistribution of N within the Cr layers.

A study was conducted to examine the surface structure of BaTi[O.sub.3] (BTO) films grown on SrTi[O.sub.3] substrates as a function of temperature. The results suggested that the surface structure of BTO films is strongly influenced by ferroelectric polarization.

A study was conducted to examine the influence of electrode roughness on the formation of metallic nanostructures made via block copolymer (BC) nanotemplates with subsequent metal loading. The results indicated that the roughness of a substrate is one of the key parameters which influenced the formation of BC nanotemplates.

The effect of both the deposition temperature and the cooling rate on the growth of calcium barium niobate (CBN) thin films on a magnesium oxide (MgO) single crystal substrate is examined. The X-ray reflectivity measurements have shown strong correlation between the density of films and their refractive indices.

A single crystal GaAs wafer with front face mirror polished is irradiated by a 1064 nm continuous laser and the damage process is examined by real-time surface reflectivity and optical distribution monitoring. The results have shown no evident melting and oxidation occurrence and the foremost damage is in the form of decomposing of GaAs surface without prominent loss of As atoms.

Low-temperature elasticity is analyzed by examining the ultrasonics, acoustic characteristics of a glassy alloy [Cu.sub.45][Zr.sub.45][Al.sub.5][Ag.sub.5]. This alloy has a large super-cooled liquid region of more than 80 K and high glass-forming ability with the critical diameter of about 9 mm.

Pump-probe reflectivity and mid-infrared (IR) transmission measurements are used for studying the low-temperature-grown GaAs (LT-GaAs) materials annealed under different conditions. The results have shown the importance of acceptor densities in the dynamic properties.

The magnetization reversal for exchange coupled polycrystalline [[IrMn/CoFe].sub.N] multilayers is examined. The results have shown how the complementary techniques polarized neutron reflectivity (PNR) and magnetic-optic Kerr effect (MOKE) are used for obtaining a layer-by-layer vector magnetometry of multilayer stacks.

'Near-frictionless carbon' is examined by neutron and x-ray reflectivity under ambient conditions, in vacuum and at elevated temperature. It is shown that the magnitude of the scattering length density of the top surface layer is greatly affected by the experimental atmosphere in which the films are contained although the trend with hydrogen in the plasma has remained the same.

A modulated reflectivity study is presented to explain the wetting layer (WL) states in molecular beam epitaxy lnAs/GaAs self-assembled quantum dot (QD) structures. The analysis reveals that any changes in the capping layer does not really affect the composition profile of the WL itself, though intermixing and the InGaAs cap layer decomposition are supposed to highly influence many of the features of such structures.

The characterization of the structural and optical properties of the sulfur incorporated [As.sub.2][Se.sub.3] crystals is studied. The analysis reveals that each diffraction curve of the crystals exhibits a large number of diffraction peaks, as the series solids are found non-amorphous, belonging to the large-grain polycrystal with medium-range order.

Contacted electroreflectance (CER) measurements in InGaN/GaN single quantum wells (SQW) light emitting diodes for different reverse bias voltages were performed to observe the effects of polarization fields and screening. Measured optical transitions and Stark shifts are compared with calculated SQW energy levels.

The structural modification in Co/Cu multilayers by 1 MeV Si(super +) ion irradiation at 77 K was analyzed by various x-ray scattering techniques. Low-angle x-ray specular reflectivity measurements are shown to be a sensitive tool to probe ion-beam mixing effects on an angstrom scale in these multilayers.

An experiment was conducted to measure the reflectivity spectra of H(sub x)MoO(sub 3) and Li(sub x)MoO(sub 3) thin films, over the photon energy range from 0.4 to 4.2 eV. The microcrystalline molybdenum bronzes have reflectances between 6 percent and 30 percent over the concentration x, range 0