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The reciprocity relation of McCumber that states that the emission and absorption spectra of broad solid-state laser transitions are related by the classical Boltzmann factor is investigated. The experiments have provided support for the McCumber relationship in erbium doped silica fiber.

The two-, three-, and four-level system terminology is used for describing lasers and are applied to many types of gain media, but are useful for comparing systems with discrete levels, pumped with a narrowband source, in near-resonance with the laser wavelength. Low-quantum-defect combinations of pump and laser wavelengths are studied for [Er.sup.3+], [Nd.sup.3+], [Yb.sup.3+] and [Ho.sup.3+] in YAG, as a function of temperature.

An electromagnetic analysis of ring-cavity-assisted amplified spontaneous emission in [Er.sup.3+]-doped Si[O.sub.2] (Er:Si[O.sub.2]) is described. The simulations are performed within the auxiliary differential equation-finite-difference time-domain (ADE-FDTD) scheme and the enhanced spontaneous emission in waveguide-coupled ring cavities with varying coupling gaps is presented.

[Al.sub.2][O.sub.3] and [Al.sub.2][O.sub.3]:[Er.sup.3+] waveguides are prepared by a reliable, low-cost and reproducible reactive cosputtering process and their optical and spectroscopic properties are examined. The gain measurements over 6.4-cm propagation length in a 700-nm-thick [Al.sub.2][O.sub.3]:[Er.sup.3+] channel waveguide has resulted in net optical gain over a 41-nm wide wavelength range with a maximum of 5.4 dB at 1533 nm.

A theoretical model is used to demonstrate the continuous-wave operation of diode-end-pumped [Er.sup.3+]:YAG lasers. The model facilitates the prediction of highly efficient operation of Er:YAG lasers with optimized gain media shape and resonator output coupling even at high temperatures beyond 550 K.

A standard ion-exchange technique was used for the fabrication of channel optical waveguides in novel Er-doped and Er-Yb co-doped ZnO-containing silicate glasses. Findings reveal the simulation of very large net optical gain for an ideal overlap of the pump and signal optical field in a glass containing at 3% of Er and no Yb.

A broad-band fiber mirror (BFM) and a tunable fiber Bragg grating (TFBG) at either end of laser cavity were used for developing a linear-cavity tunable erbium-doped fiber laser (TEDFL). Results suggest the achievement of a side-mode suppression ratio of 57.9 dB, wavelength tuning range up to 30 nm with step resolution of 0.2 nm and power variation less than +1.0 dB.

Mutual injection-locking theory of two individual fiber lasers is discussed. Results suggest the achievement of interference fringes with high contrast ratio.

A novel optical flip-flop (FF) memory cell based on Er-doped devices is presented. Findings reveal the possibility of regulating the transients by properly choosing signals wavelengths and powers.

A newly developed model of the longitudinally laser diode (LD) pumped erbium-ytterbium-codoped phosphate glass microchip laser with cooperative and cumulative upconversions is discussed. The conversions are found to highly affect the threshold and slope efficiency of the lasers.

Several test patterns integrated with microheaters are used to analyze and characterize the cross-plane and in-plane Seebeck coefficients for ErAs: lnGaAs/ lnGaAlAs superlattices with different carrier concentrations. The results show that a heterostructure thermionic emission takes place in the cross-plane direction, which can be proved to be an after effect of the decrease in the Seebeck coefficient with increasing carrier concentrations.

A new all-optical automatic gain control (AGC) scheme using a semiconductor OA(SOA)-based feedback for controlling the Erbium-doped fiber amplifiers (EDFA) pump power is presented. The method helps in greatly reducing the transient effects without producing power oscillations on the surviving channels.

Half-Heusler compounds ErPdX (X = Sb and Bi) are prepared by a spark plasma sintering method and their thermoelectric properties at high temperature and thermophysical properties at room temperature are evaluated. The maximum values of the dimensionless figure of merit ZT of ErPdSb and ErPdBi are 0.16 around 699 K and 0.075 at 495 K, respectively.

The status and benefits of metal source/drain (S/D) Schottky-barrier (SB) MOSFET technology are discussed. SB MOSFET technology state of the art is examined and shown to be focused on barrier-height-lowering techniques that use interfacial layers between the metal S/Ds and the channel region.

A detailed study of the evolution with annealing temperature of the morphological and structural properties of thin erbium oxide (Er2O3) films evaporated in an electron beam gun system is presented. The observations show a shift of a flatband voltage to the positive side and significant lowering of the positive charge down to ~1 X 10(super 10) cm(super -2).

Single crystal infrared (IR) reflectance spectra for the Dy3Al5O12 and Er3 Al5O12 compounds, their corresponding optical constants, as well as a discussion concerning the vibrational, dielectric, and elastic properties of various members of the rare earth aluminum garnet family is presented. By using a modification of the semiempirical Brout's formula, the bulk moduli have been determined and are compared to those derived from interatomic potential calculations.

The presence of 1.2 mol % of Nd(super 3+) ions influences an effective deactivation process of the lowest excited states of Er(super 3+) and Ho(super 3+), decreasing the lifetime from 10 to 1 ms and from 17 to 2 ms, respectively, in Er: Nd: YLF and Ho:Nd: YLF crystals.

The synthesis and characterization of near-infrared (NIR) emitting complexes of Nd(III), Er(III) and Yd(III) based on hexacoordinate lanthanide ions with an aryl functionalized imidodiphosphinate ligand, tpip, are described. The results indicate the effective shielding of the lanthanide by the twelve phenyl groups of the tpip ligands and the reduction of high-energy vibrations in close proximity to the lanthanide, which are the two important features in the design of NIR emitting lanthanide complexes.

Room temperature 1.54 mum electro luminescence (EL) was observed from Au/SiO(sub 2):Er/n(super +)-Si and Au/SiO(sub x):Si:Er/n(super +)-Si diodes. A SiO(sub x):Si:Er film deposited on a n(super +)-Si substrate by the magnetron sputtering technique was revealed to be a promising material for efficient Er(super 3+) EL.

Infrared emission at 1.54 mu m excited optically and electrically is observed from an erbium organic compound tris(acetylacetonato) (1,10-phenanthroline) erbium [Er(acac)3 (phen)] to fabricate an electroluminescent (EL) device. The device shows infrared EL emission at 1.54 Mu m, and is a simple and cheap method to obtain a light source for 1.54- mu m- wavelength devices in optical communications.

A large reversible magnetocaloric effect (MCE) near the ordering temperature has occurred and the values of the maximum magnetic-entropy change has reached 18.3 J[kg.sup.-1][K.sup.-1] for the field change of 5 T with no hysteresis loss around 17 K. The results have shown that [Er.sub.4]NiCd is a promising system for magnetic refrigeration at temperatures below liquid [H.sub.2].

The different emitting centers within Si[O.sub.2] codoped by [Er.sup.3+] ions and silicon-excess are examined. The energy transfer from silicon-oxygen-deficient centers (SiODCs) toward the Er ions is described, especially as the emissions from the Si-based entities (SiODCs, Si-nc) and from some transitions of Er ions located in a same visible broad range.

Silica films doped with erbium are prepared on silica glass substrate, where the inorganic-organic hybrid sol-gel method is used for preparing the films and the Na codoping induced the crystallization of silica film. The annealing temperature and atmospheres have large effects on the local environment of [Er.sup.3+] and the photoluminescence (PL) intensity is improved by suitable heating treatments.

The impact of temperature on the controlling of the local devitrification process taking place in an oxyfluoride glass doped with [Er.sup.3+] ions under diode laser irradiation is analysed. The formation of nanocrystals due to the observed laser action is also discussed.

A series of [Ce.sup.3+]:[Yb.sup.3+]:[Er.sup.3+]:NaLa[(W[O.sub.4]).sub.2] crystal powders are prepared by high temperature solid phase reaction. A quasicontinuous-wave laser around 1.55 [micro]m is realized when a 2.61 mm thick c-cut slice of the crystal is pumped by a diode laser.

Strong Stark splitting, which is independent of the R-ions replacement, is observed through the photoluminescence investigation of electronic ferroelectric [Er.sub.1][Yb.sub.x][Fe.sub.2][O.sub.4]. The unusually large Stark splitting at visible range has shown the existence of strong local field originated from the W-layer in the charge-frustrated Er[Fe.sub.2][O.sub.4].

Multilayer thin films consisting of nanometer-thin, Er-doped luminescent layers interlaced with nanometer-thin, St-rich sensitizing layers are described as a solution to loss of [Er.sup.3+] optical activity during nanocluster Si (nc-Si) sensitization of [Er.sup.3+]. High-resolution transmission electron microscopy and photoluminescence (PL) spectroscopy have helped in maintaining the compositional and structural integrity of the heterolayer thin film by using nitride layers and the subsequent maintenance of subnanometer scale spatial separation between nc-Si and [Er.sup.3+] even after high temperature annealing as being the key factors for the advantage of the heterostructure.

The various effects of the deposition temperature of substrate heating on the energy transfer taking place from the Si-nanoclusters to the Er ions inside the silicon-rich silicon oxide layers are demonstrated. The Er ions are shown to exhibit an efficient indirect excitation with an increase in the deposition temperature above 200 C.

The synthesis, crystal structure and the magnetic properties of the series of the electron-doped orthorhombic-pervoskite maganites, [Ca.sub,0.9][R.sub.0.1]Mn[O.sub.3] perovskites (R = rare-earth) are explained. The results demonstrate that the temperature magnetization and paramagnetic susceptibility of the composites are highly dependent on the ra dius of the R ion that is inserted in the compounds.

The article employs a rate equation approach for studying the different conditions that are required for the generation of optical gain in the waveguide-confined nanocluster-sensitized erbium in slot waveguide geometry. A new approach for reducing the carrier absorption taking place in the system is also proposed.

The energy transfer mechanism among silicon nanoparticles (Si-np), both amorphous and crystalline, and Er ions in a silicon dioxide matrix is analyzed. A model is developed in which the internal intraband recombination within Si-np is competitive with the transfer process via an Auger electron-erecyclingE process and the studies have recast the role of Si-np in the sensitization scheme, where they are able to excite very efficiently ions in close proximity to their surface.

Several studies are conducted to explain the applicability of the upconversion of the subband-gap photons in the enhancement of the efficiency of the silicon solar cells. The quantum efficiencies achieved by the silicon solar cell and the applied upconverter are also determined.

Several studies are conducted to explain the spectroscopic, as well as the upconversion properties exhibited by the erbium-doped potassium lithium tantalate niobate crystals under different conditions. The crystals are shown to lead to green emissions during the excited state absorption and energy transfer processes.