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A high efficiency Yb:YAG/YAG composite slab laser is presented, in which the corner-pumped scheme is adopted. The slab is a composite crystal of Yb:YAG bonded thermally with undoped YAG at both edges. The pump light from diode arrays is coupled into the slab through four chamfers at the four corners independently. The pump absorption efficiency is studied, and an analysis method has been developed as a guide to optimize the geometric parameters of the composite slab, to obtain higher pump absorption efficiency and uniformity. The influence of the internal thermal lens on the laser resonator is analyzed. A 1016 W continuous-wave output has been obtained with the slope efficiency and optical-to-optical efficiency of 42.8% and 34.4%, respectively. OCIS codes: 140.3460, 140.3480.

Vanadium dioxide (V[O.sub.2]) and vanadium pentoxide ([V.sub.2] [O.sub.5]) thin films are irradiated by a near-infrared continuous-wave laser beam and the dynamic optical limiting performance is measured. The temperature varying with time of the films induced by a laser beam is also recorded by an IR thermal sensor. Under the irradiation of a laser beam with an intensity of 255 W/c[m.sup.2] and a spot diameter of 2 mm, the laser beam transmittance of the V[O.sub.2]2 film decreases from 47% before phase transition to 28% after phase transition, and the response time is ~200 ms; the laser beam transmittance of the [V.sub.2][O.sub.5] film decreases from 51% before phase transition to 24% after phase transition, and the response time is ~40 ms. The optical limiting is realized by this laser heating-induced phase transition. OCIS codes: 140.3360, 310.6860, 120.6780, 140.6810.

C[r.sup.3+]:LiSrA1[F.sub.6] crystals are an interesting laser medium because of their spectroscopic characteristics: They present a broad emission band in the near infrared and can be pumped either by a flashlamp or by diodes. Up to now, their limitation has been mostly due to their poor thermal properties that limit the laser performance either in the repetition rate in a pulsed system or output power in cw systems. We have designed and constructed a flashlamp-pumped laser using a standard rod pumping cavity that avoids most of the heat generated in the pumping process and allows operation at a fairly high repetition rate of 30 Hz with a high average power of 20 W in a conservative operation mode. OCIS codes: 140.4780, 140.6810, 140.5680, 140.4480, 140.3410.

This paper is a summary of an experiment using Fresnel enantiomorphic diffraction in geodetic laser methods. In this study, results from the analysis of a large data set made possible the determination of the degree of accuracy of laser beam axes under various surveying conditions. An important part of the results is formed by the conclusions derived from the discussed method in specific geodetic applications, the advantages, as well as the disadvantages of the laser method, its comparison to conventional surveying methods, and an outline on further research. DOI: 10.1061/(ASCE)0733-9453(2006) 132:2(71) CE Database subject headings: Geodetic surveys; Lasers; Diffraction.

A maximum-likelihood estimator used to determine boresight and jitter performance of a laser pointing system has been derived. The estimator is based on a Gaussian jitter model and uses a Gaussian far-field irradiance profile. The estimates are obtained using a set of return shots from the intended target. An experimental setup with a He-Ne laser and steering mirrors is used to study the performance of the proposed method. Both Monte Carlo simulations and experimental results demonstrate excellent performance of the estimator. Our study shows that boresight estimation is more challenging than jitter estimation when both quantities are estimated. Furthermore, their estimation performance improves with an increase in the number of shots. The experimental results are found to agree well with the simulation results.

A theory for intersubband lasers, based on the solution of the Maxwell-semiconductor Bloch equations for the laser field and active medium is presented. The collision contributions are treated within the relaxation rate approximation, where the relaxation rates are determined by microscopic scattering calculations.

A system for the course control and spatial stabilization of the output beam of a femtosecond laser system is realized. An accuracy of 0.5 [micro]rad is achieved long term in a laboratory environment for a beam with an initially daily deviation of more than 40 [micro]rad. The application and importance of the method is illustrated for laser pulse shortening in a hollow waveguide resulting in a stable output power and an 8 fs pulse duration for more than 10 h operation time. OCIS codes: 140.7090, 320.7160.

In this paper, a novel laser droplet formation process (LDFP) from a metal wire is investigated. The process consists of the formation of a molten pendant droplet and its detachment, which are both unstable and influenced by numerous process parameters. The goal of the investigation is to specify the main process parameters and the values that provide for stable and repeatable process. Based on theoretical and experimental consideration of LDFP, a methodology for estimation of process control parameters is proposed. Estimation of the parameters is demonstrated on examples of deposited droplets of nickel and tin-alloy wires. Experimental results on tin-alloy wire indicate that the problem of splashes on the substrate is still present, while those on nickel reveal an acceptable formation of droplets. [DOI: 10.1115/1.2120780]

Four laser scanning schemes for tube bending, including point-source circumferential scanning, pulsed line-source axial procession, and line-source axial scanning without and with water cooling are investigated in numerical simulation. The coupled thermo-mechanical model established using the finite element method is validated and applied to predict the bending deformation and help better understand bending mechanisms under different schemes. The influence of important parameters such as beam coverage, scanning velocity and cooling offset on the deformation is investigated in detail. Parametric studies are carried out to determine proper processing windows at which the largest bending can be obtained. The deformation characteristics, including the wall thickness variation and the cross-section distortion produced by different scanning schemes are analyzed, along with the processing efficiency. [DOI: 10.1115/1.2113047]

Relative intensity noise (RIN) characterization of triangular ring lasers, fabricated through a self-aligned dry etching process in InGaAsP-InP is presented. Two different classes of ring laser behaviors are identified, showing clear dependence of RIN enhancement on the backscattering strength.

The in-plane polarization anisotropy of gain in CS GaInAsP-InP Q-wires including band mixing effects that happen because of elastic strain relaxation and from 2-D confinement is studied. Strong strain relaxation causes in-plane polarization anisotropy to show complex, non-monotonic dependence on the wire width as per calculations obtained.

A tunable photonic crystal coupled-cavity laser diode based on InP was developed and the tuning characteristics were compared with results from a transfer matrix model. The simple model, promising in its output characteristics could be used for monolithic integration into highly integrated photonic circuits.

A set of dynamical equations for single mode erbium distributed feedback fiber lasers was obtained keeping in mind spatial hole burning and the nonuniform modefield distribution. The spatial distribution of the laser mode was found to play a significant part in determining the output characteristics of the laser.

An aluminosilicate neodymium-doped fiber laser tunable in the 0.9-Mum wavelength range was studied for spectroscopic and tuning characteristics. A W-type core refractive index profile facilitated operation on the 0.9- Mum three-level transition in neodymium-doped double-clad fiber laser.

The design and implementation of a three-mirror Nd:YVO4 solid-state laser with an optimized aspheric third mirror was done. The spatial-mode characteristics were studied and it was confirmed that enhanced spatial-mode selection and mode-shaping could be achieved.

The possibilities of Tm:KGdW as a tunable 2- Mum CW laser at room temperature is investigated. Comparisons are made of the doping levels, pump wavelengths and polarization configurations and the advantages of the monoclinic double tungstates over other Tm-hosts are shown.

Two parameters valuable for laser design and power scaling are obtained by studying the evolution of thermal lensing versus absorbed pump power. The experimental features are explained and quantum efficiency of the samples is inferred through an analytical model that is developed.

A comprehensive time-domain noise model for vertical-cavity surface-emitting lasers is presented. The model is based on a deterministic quasi-three-dimensional dynamic model that treats the carrier transport heat generation and dissipation, and optical fields in the device.

Laser ultrasound is a technique used for the ultrasonic inspection of composites during manufacturing of advanced jet fighters. With this technique laser interferometry is used to detect ultrasonic displacements generated by a laser. In theory, the signal-to-noise ratio is proportional to the square root of the collected detection light. In practice, laser phase noise limits the signal-to-noise ratio above a certain collected light level. Two techniques are presented to decrease effects due to laser noise. In one technique the dual-cavity Fabry-Perot currently used is replaced by an interferometer based on a photerefractive crystal. The other technique has a high-finesse Sagnac cavity that filters the phase noise from the detection laser. Experimental results demonstrate that these two techniques significantly reduce limitations due to laser noise. OCIS codes: 120.3180, 120.4290, 120.2230, 190.7070.

The chemical oxygen-iodine laser (COIL) with a new chemical method of atomic iodine production is investigated, wherein iodine atoms are formed in the COIL cavity by the fast chemical reaction of hydrogen iodide with chlorine atoms that are also produced chemically. The variation of the iodine concentration along the gas flow in the laser cavity was considered very small, indicating a low rate of iodine atom recombination.

A comprehensive description is given of the design of compact femtosecond solid-state lasers that are based on novel multipass cavity (MPC) configurations to extend the resonator length. To investigate the limits of compactness and energy scaling, two-mirror MPC geometries are examined.

The threshold current temperature characteristic of highly strained InGaAs-GaAs double-quantum-well vertical-cavity surface-emitting lasers (VCSELs) in relation to the gain-cavity detuning at room temperature at room temperature is presented and assessed. A conceptual model that relates the gain-cavity detuning at room temperature sensitivity of the active region performance, which qualitatively describes the threshold current-temperature characteristic typical of VCSELs is proposed.

Q-switched and CW passive mode locking in a laser-diode-pumped Nd:GdVO(sub 4) laser with a semiconductor saturable absorber mirror has been demonstrated. The repetition rate of the Q-switched envelope increased from 23.1 to 260 kHz as the pump power increased from 1.75 to 13.0 W. At a pump power of 13.7 W, the Q-switched mode locking changed to CW mode locking.

A study has been done to measure the thermal lens in an Nd:YAG rod to be reduced by more than an order of magnitude when cooled with liquid nitrogen. It has been shown that cryogenic cooling resulted to a considerably enlarged power range for stable laser oscillation.

An optoelectronic design has been presented that integrates vertical-cavity surface-emitting lasers (VCSELs), optical emission filters and PIN photodetectors through a modification to a typical VCSEL structure and system designs have simulated and compared. VCSELs operating at 773 NM with one bottom N-type interactive contact showed CW single-mode and multimedia operation and output powers over 0.6mW, which is sufficient for high-quality sensors.

Strong optical bistability in a widely tunable L-band erbium-doped fiber ring laser pumped by a 980-nm laser diode is demonstrated. This simple configured laser gives strong optical bistability with added advantages such as control of the opeartion wavelength that can cover from 1560 to 1584 nm.

An optical feedback device that allows adjustment of the characteristic timescales of oscillations is described. The device could be made to oscillate at gigahertz frequencies making it suitable for chaos communication systems.dbi

A prepulse-free Nd:glass PW laser system of 0.9-PW peak power is developed to heat a pre-imploded high-density plasma. Specifications of the PW laser have also been summarized.

Novel method for saturation factors of absorption under optical pumping in solid-state lasers depends on the pumping scheme. However, it is through lasing that the saturation effect is recovered.

A diamond window has been used to cool high power Nd:YV04 laser head. The lasing slab that is pumped through the transparent chemical vapor deposition (CVD) diamond window, removes the heat from the pumped region.

The stability of pulsed emission in self-mode locked quantum cascade (QC) lasers is demonstrated. The enhancement of intracavity second-harmonic generation (SHG) as a result of high peek power is also observed.

The dynamics of injection-locked vertical cavity surface-emitting lasers (VCSELs) is studied as a function of temperature of the slave device. To take advantage of the stable locking region, the VCSEL device should have a minimum carrier density of 40 K -50 K below room temperature.

The scanning voltage microscopy (SVM) results on actively driven buried heterostructure (BH) multiquantum-well (MQW) lasers that exhibit current blocking failure at current injection operation are reported. Application of the SVM method assists in diagnosing the origins of externally-observed active optoelectronic devices such as lasers, modulators, and detectors.

The results of a theoretical model that is built to describe the temperature-dependent lasing characteristics of InAs-InGaAs quantum-dot (QD) lasers operating at 1.3 mu m, are reported. An improved model that allows both free carriers and excitons in the dots is introduced to adequately describe the performance of the lasers.

CW performance of multiquantum-well (MQW) GaAs-AIGaAs lasers, operating near 850 nm at 300 K, is investigated as a function of the doping level in the p-cladding layer. The internal quantum yield is found to be close to unity and optical losses are as low as 1.36 1/cm at the highest level of doping.

The experimental observations of the current-induced polarization switching, in vertical-activity surface-emitting lasers, accompanied by a decrease of the total output power at the switching point, are reported. It is concluded that the experimentally observed polarization switching, is from the mode with higher unsaturated net gain to the mode with lower unsaturated net gain.

The optical properties of the laser-machined channel are affected by the residual ablated material remaining in the atmosphere of the channel during femtosecond-laser deep hole drilling. The interplay between hole drilling, beam propagation, and non-liner beam interactions are demonstrated.

The study presents a quantum theory for the noise of optical pulses in actively mode-locked lasers with phase modulation and/or group velocity dispersion. It is useful for understanding the noise of chirped optical pulses in mode-locked lasers and is relevant to semiconductor mode-locked lasers.

The behavior of a vertical-cavity surface-emitting lasers(VCSELs) having two transverse modes with parallel polarization, which interact with an externally injected CW optical field, is numerically analyzed. Different dynamics regimes were found, varying on the injection strength and frequency of the injected field.

Based on the spatially independent model and the numerical results algorithm, the behaviors of the transverse mode competition of vertical-cavity surface-emitting lasers (VCSELs) are investigated and analyzed. The results are helpful to design and control the transverse mode characteristics of the output optical power of a VCSEL.

A 2-kW-class chemical oxygen-iodine laser (COIL) using nitrogen buffer gas is developed and tested since industrial applications of COIL devices would require the use of nitrogen as the buffer gas. The laser, with a gain length of 11.7cms, is energized by a square pipe-array jet-type singlet oxygen generator (SPJSOG) and employs a nozzle bank with a designed Mach number of 2.5.

An experimental and theoretical investigation into the low-frequency intensity noise characteristics of erbium-doped distributed feedback (DFB) fiber lasers is presented. In order to predict the intensity noise generated in a linear fiber laser and explain the observed noise characteristics, an analytical model is used.

The extent of overtone small-signal gain data measured while operating a small-scale hydrogen-fluoride (HF) laser is compared with fundamental lasing output spectra and spontaneous overtone emission spectra. The data are consistent with an equilibrium rotational distribution discussing the results in terms of their applicability to the question of rotational nonequilibrium in continuous wave HF lasers.

A presentation of a novel modelocking technique is given in which the intensity-dependent mode-coupling dynamics of a long-period fiber grating is used to achieve modelocking in a passive optical fiber laser. It is shown through numerical studies of the pulse-shaping mechanism that the laser produces stable mode-locked soliton-like pulses.

The length of the pulse generated in a passively Q-switched Nd: YAG/Cr(super 4+): YAG microchip laser is increased and the pulse energy is decreased by bleaching of the saturable absorber by pump light. Both these effects are important in short-pulse microchip lasers.

An experimental investigation of the bifurcation structure of phase space is done in an erbium-doped fiber laser with a sinusoidal pump modulation. The prediction of the behavior of the fiber laser is allowed by systematic organization of coexisting attractors when initial conditions are allowed to evolve to their final states.