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We study pump-probe spectroscopy of Rb vapor. Absorption spectra are presented for a weak probe beam in a room temperature vapor subject to a strong counter propagating pump beam of identical frequency. The importance of hyperfine pumping in the formation of the sub-Doppler spectrum is explained. For typical experimental parameters we clarify why the standard designation of 'saturated absorption' spectroscopy is a misnomer. In contrast to saturated absorption, the details of the transient solution are crucial and hyperfine pumping leads to a modification of the absorption for detunings of many tens of natural linewidths from resonance.

Using resonant-ultrasound spectroscopy, beryllium's elastic constants for both a monocrystal and a polycrystal, is measured in this study.

This article discusses the Theory of Colors, as conceived by Johann Wolfgang von Goethe and Newton, in scientific terms and explanations. The research centers around natural optical phenomena of colors that leads to the creation of a symmetric color circle, which includes spectral and nonspectral colors.

Research describing a method of shape determination for nanocrystals in composite materials is presented. In particular the use of optical extinction spectroscopy with polarized light is shown to have applications in this field.

Research describing single quantum well structures with high indium content is presented. In particular photoluminescence, spacially resolved and optical pumping spectra are investigated.

Research is presented concerning the investigation of thermal stability and continuity of thin barrier layers which prevent the diffusion of the Cu atom into low-dielectric constant (k) silica films by positron annihilation lifetime spectroscopy.

Research is presented concerning the analysis of the photoluminescence spectrum of the radiative recombination process occurring between a valence-band hole and a conduction-band electron.

Research is presented concerning the measurement of multiphonon relaxation rates and decay to investigate the spectroscopic characteristics of ZnCl2 based glasses which had been doped with Ho3+.

Research is presented concerning the use of photoluminescence spectroscopy to investigate the optical transitions in multiple quantum well microdisks of In0.22Ga0.78N/In0.06Ga0.94N which have a diameter of 6.0-micrometers.

Research describing a method of obtaining an optical density spectrum free of interference fringes is presented. The process is applicable to amorphous silicon thin films subjected to hydrogenization.

In this paper a new approach is presented to explain the formation of Talbot's bands by using the model of tilted pulse fronts. Numerical calculations of this model are presented. Another interpretation of Talbot's original paper is also given and explained. Simple experiments, suitable for students' laboratory practice, have been used to carefully study the dependence of the visibility of the bands on different properties of the plate: thickness, refractive index, dispersion. Photos of Talbot's bands are also presented.

We present an apparatus for demonstrating the Alford-Gold effect (in the more complete case of a continuous optical source) which uses only cheap commercial components such as a diode laser, a coil of optical fibers, and a photodiode. The effect is introduced on the basis of intuitive arguments; the experimental results are compared with the theoretical predictions that were first obtained by Givens and by Mandel. The demonstration turns out to be, both for graduates and undergraduates, an instructive exercise in modem coherence theory.

Results demonstrate that scanning tunneling microscopy and the generated spectra are useful in studying the local process-related damage of silicon oxide ultrathin films during fabication of devices. Data further show that ion-beam damage of the film is recovered during thermal annealing.

A subdynamics-based general formulation was derived for the construction of the spectral decomposition of the Hamiltonian for N excitons limited by a quantum dot with parabolic potential and mediated by an electromagnetic field. Using the formulation, the spectrum of the Hamiltonian of N excitons can be computed based on recurrence relations for the operators of creation and destruction. Then the spectral decomposition of the Hamiltonian of the system can be constructed using the intermediate operator and the intertwining relation.

A study was conducted to demonstrate the possibility of using a single-beam, dual-arm approach to cavity ring-down spectroscopy to lock a narrow-band external-cavity diode laser to a high-finesse resonator supporting one arm. A spectrum of water vapor was determined in the ambient air. Results indicated that the approach permits ring-down decay acquisition rates that are hindered by the ring-down and buildup constants of the resonator.

The photoluminescence (PL) and PL excitation spectra of individual Er centers in GaAs:Er,O and AlGaAs:Er,O were measured by site-selective luminescence spectroscopy. Similarities in the spectra follow the similarities of the centers and became the bases for the grouping of the centers into different classes. A major part of the Er centers in GaAs which was formed under oxygen codoping contained two oxygen atoms and two arsenic atoms at the nearest-neighbor sites of the Er atom.

An investigation of the properties of electron traps in nominally undoped In1-xGaxAsyP1-y layers grown on GaAs0.61P0.39 substrates by liquid phase epitaxy was conducted using deep level transient spectroscopy measurements. Only one type of electron trap with the activation energy of 0.38 eV was seen in In0.32Ga0.68P while a new type of electron trap with the activation energy of 0.15 eV began to show and its concentration increased as the As composition was increased. However, this trap was not detected in GaAs0.61P0.39. Other observations are presented.

Low-energy electron microscopy (LEEM) and metastable electron emission microscopy (MEEM) were used to study images and local electron spectra of an oxide pattern on Si(100) in which energy-filtered images were seen for the first time. Results of the study revealed that LEEM provides averaged information on several surface layers while MEEL gives the information on the outermost surface layer selectively. Other observations are discussed.

Research on the factors limiting the resolution of correlation of deep level transient spectroscopy (DLTS) is conducted. The selectivity and sensitivity of DLTS depend significantly on the choice of the correlation function. The limitation involves the weighting functions as being effective filters only for slow transients. A correlation procedure, based on the Gaver-Stehfest algorithm for the inverse Laplace transformation is proposed to overcome the limitation.

Four peak absorptions caused by transitions between pairs of ground and the first excited tunnel-coupled states in double quantum wells were observed when a comparison was done of the ordinary and differential absorption spectra for the different biases. The differential absorption spectra were found to be useful for IR transition of electrons in double quantum wells investigations.

The dependence of spectral line shape on sample-probe reactions are determined using an analytical model. The model uses a focused probe to study the discrete sampling of spatial property changes in spectra. The model reveals that probe channeling near the free surface and gradient-stimulated line broadening are the primary causes for the influence exerted by sample probe reactions on the shape of spectral lines.

The InP optical constants for photon energies in the range of 0.75 to 5.0 electron volts are determined using the technique of variable angle spectroscopic ellipsometry. The photon energy range includes the 1.35 electron volt region, which represents the fundamental gap. Analysis of the optical constants reveals that the dielectric function of InP obeys the Kramers-Kronig law above 1.35 electron volts.

Three different factors influence the width of the spectral output from the amplifier of an optically pumped high-power D2O laser system. Narrow spectral outputs of about 10 megahertz width are obtained when the D20 gas pressure is between 6 and 7 Torricelli, the intensity of the laser beam is more than 50 Weber per square centimeter and the oscillation frequency is between 15 and 35 megahertz. The D2O laser system is operated using a configuration with an oscillator-amplifier.

The deep trap energy (E(T)) and deep trap concentration (N(T)) in GaAs are determined by a new method, which does not require the emission-rate data. The method involves measurement of capacitance at different forward bias voltages. The concentration of the various deep trap centers such as EL6, EL3 and EL2 are determined by considering the lambda effect. N(EL2) has a value of 1.14 times 10 to the 16th power per cubic centimeter and E(EL2) has a value of 0.71 electron volts. N(EL6) has a value of 8 times 10 to the 15th power per cubic centimeter and E(EL6) has a value of 0.42 electron volts.

Use of the transfer matrix technique in a study of the transmission of electromagnetic waves in cylindrical, planar and spherical double-barrier resonant tunneling, single dielectric layers and multiple period Bragg reflector systems reveals that the coherence of wave propagation produces peculiar features in the transmission spectra. The peculiar spectral features are limited to spherical and cylindrical geometries.

A homemade grating spectrometer and simple electronics allow measurements of the energy gap of semiconductor samples in introductory laboratory courses. Both transmission spectra and 'photoconductive effect' spectra may be obtained. Results for Ge, Si, GaAs, and InP are reported.

Modern materials science requires processing and characterization techniques for microscopic structures. Molecular probes such as Raman spectroscopy are some of the most viable tools, particularly if they are supplemented by imaging to obtain spatially resolved compositional information of inhomogeneous or low volume samples. In order to introduce these techniques and materials science experiments into the advanced undergraduate laboratory, we have constructed an inexpensive micro-Raman attachment, which consists of an off-the-shelf microscope and the coupling optics to an existing Raman spectrometer. The modification of the microscope, the optical coupling, and a low cost viewing system for positioning the laser excitation on the sample are described in detail. The students study molecular spectra of new materials such as diamond films, Fullerenes, and biological compounds with spatial resolution of several microns.

Pre-evaluation of spectroscopic ellipsometric measurements is aided by backpropagation network. The multilayer feedforward network which performs nontrivial mapping functions is used on separation of oxygen structure by implantation and evaluation of depth profile of damage due to ion implantation.

Admittance spectroscopy is used to measure valence-band discontinuities in Be-doped GaAs/AlGaAs multiple-quantum-well structures. Valence-band discontinuity has a value of 0.165 electron volts and can be inferred from differences in the measured condition-band discontinuity and expected total band-gap discontinuity. Admittance spectroscopy involves the use of a HP4274A multifrequency LCR meter.

The study of triply-ionized holominum ions in single-crystal KYF4 reveals the presence of two completely different groups of crystal field sites. The study involves the use of Fourier-transform spectrometer at 80 and 2 degrees kelvin. Six sites which are in coordination with the crystallographic data are yielded by the presence of three dissimilar sites in KYF4.

A study of the aging properties of CF4/iC4H10 genes, a function of gas mixture ratio, indicates the existence of two deposition regions and two etching regions. Auger electron spectroscopy is used in the analysis of anode surfaces. Aging, which is caused by CF4, is found in etching deposits, but has little influence on gold plates. Plasma chemistry in avalanches is interpreted by low-pressure radio frequency plasma chemistry principles.

A dielectric relaxor is synthesized and undergoes first order phase transition to a ferroelectric state. A Vogel-Fulcher anomaly of the dielectric constant occurs in the dielectric relaxor when it is in the relaxor state and the freezing temperature is near the phase transition temperature. Presence of defects and lead vacancies into the dielectric relaxor material impedes spontaneous phase transition.

The formula for the cosmological spectral shift in a Robertson-Walker universe is derived by applying the method of separation of variables to the solution of Maxwell's field equations. A proof is also given of the formula for the variation of the apparent brightness of a source with distance.

The energy levels of trivalent thulium in the laser host crystal yttrium aluminum garnet (YAG) are investigated. Two YAG crystal samples containing different concentrations of thulium are prepared by the Czochralski method. The crystals'absorption and fluorescence spectra are recorded at various wavelengths using aspectrophotometer and a double monochromator, respectively. Results reveal the presence of a number of Stark levels that deviates from those obtained by crystal-field splitting calculation for Tm3 ions in yttrium aluminum scandium garnets.

The structural and chemical profiles across two thin silicon oxide-nitride-oxide (ONO) structures are studied by electron holography, microscopy and energy-loss spectroscopy. The ONO structures were grown at a low temperature level of 300 degrees centigrade. Results show that computer-controlled parallel electron-energy-loss spectrometry is capable of obtaining a chemical profile across the layers, provided small accumulation times are used. Electron holography is also found to very useful for the imaging of stacked ONO structures.

A photomixer for generating coherent radiation in the millimeter-wave regionsof an electromagnetic spectrum is presented. The photomixer consists of two sets of interdigitated metal electrodes positioned on the top surface of a low-temperature-grown GaAs material. The excellent photoconductive properties of the GaAs material make it possible for the spectrum photoconductance to be approximated as an ohmic conductance. Experimental tests show that the proposedGaAs photomixer is capable of achieving pulsed conversion efficiencies of more than 10%.

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 properties of point defects in single crystals of lithium triborate are investigated using electron paramagnetic resonance (EPR), electron-nuclear double resonance (ENDOR), optical absorption and thermoluminescence (TL). Magnetic resonance data for both the EPR and ENDOR spectra are obtained by means of a Bruker Model ESP300 spectrometer. The TL data are taken using an RCA photomultiplier. The spectra are then irradiated with 60 kilovolts x-rays. Results show that the EPR spectra exhibits two point defects, one holelike and the other electron-like.

A new technique for the decomposition of closely spaced interface and bulk deep trap states was presented. The technique utilizes temperature-dependent pulse-width deep level transient spectroscopy to separate two bulk trap states and one continuously distributed interface state in a Pt/CdS photodiode, thus allowing a more accurate measurement of the physical parametrs to be obtained.

Deep-level transient spectroscopy (DLTS) and constant-capacitance DLTS (CC-DLTS) measurements of selenium-related DX centers in AlGaAs were compared to investigate the influence of refilling effects on obtained values. CC-DLTS measurement revealed the existence of one DX center while DLTS indicated two. The results showed that DLTS measurements were greatly affected by refilling effects which occur during capacitance transients. However, the refilling effects did not affect CC-DLTS measurements.