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The band structures, absorption coefficient due to intervalence subband transition and optical gain in mid-infrared type II InAs/GaInSb/A1Sb interband cascade lasers are determined using an eight-band k.p model. It is shown that the band structures for the A1Sb/InAs (25 angstrom)/GaInSb (34 angstrom)/A1Sb quantum well active region in a type II interband laser at 800 and 300 Kelvin are a function of an in-plane wave vector.

There are basically four different models for representing the mechanism of energy transport during short-pulse laser heating. They are the parabolic one-step model based on the classical Fourier conduction law, the hyperbolic one-step model which was postulated for gases, and the parabolic two-step and the hyperbolic two-step models. The two-step model involves two coupled energy equations governing the heat transfer in the electron gas and the metal lattice.

The quantum limit of a laser amplifier which is used as a detector is calculated, wherein it is observed that the amplified output and detector readout are quantum correlated. A nonclassical, sub-Poissionian minimum uncertainty state can be prepared by a laser amplifier detector, while its use as an information tap remains limited due to the added spontaneous emission noise.

Time-of-flight mass spectroscopic analysis of the laser ablation of polystyrene and polymethylmethacrylate films at 308 nm reveals that the neural fragments from the polymer surface are monomer styrene, and monomer and dimer methylmethacrylate. The monomeric and dimeric forms in the mass spectra indicate the occurrence of 'unzipping' of the polymer films. The production of the fragments depends on the kinetic energy profiles and ablating laser fluence, indicating that the polymers undergo photothermal and thermal dissociation during the experimental process.

Byline: W. Weingartner, A. Kaplan, D. Schuocker In conventional laser machining processes the melt is removed by an intense gas stream, which ejects the liquid material usually in the direction of the laser beam. A new method is described here, whereby the molten material is sucked into a bore coaxial to the beam and then taken away by a fast horizontal gas jet. The vacuum in the suction bore is obtained by fast expansion of highly compressed air. This design is then used to cut 1.25 mm mild steel under the variation of several parameters. It shows very similar results to conventional cutting processes, only the characteristic appearance of the top and bottom kerf edge being changed upside down.

The effect of process parameters such as laser intensity, scanning velocity on the bending deformation of thin sheet metal with different thicknesses is examined. The studies have shown that because of the coupling effect of two mechanisms, the smoothly switching from one mechanism to the other depending on process conditions has made the laser peen forming to be an easily controlled process for forming complex shapes and high precision curvature modification.

Random laser action is obtained in a diffusive weakly scattering regime by using an alcohol solution of rhodamine with silica nanoparticles prepared by the Stober method. Particle size and concentration has affected the random laser performance and silica nanoparticles have contributed for a much slower photodegradation of the dye molecules than titania nanoparticles that is used in the majority of the dye random lasers.

A numerical and an experimental method is used for studying how the shape of parts obtained through the LASER cladding process is controlled by application of an ac magnetic field. The studies have shown that straight metallic joints of high aspect ratio is obtained by using inductors of triangular cross-section that concentrate electromagnetic forces at the bottom of the joint.

A continuously tunable, phase-locked, single-frequency, continuous-wave (cw) terahertz generator around 120 GHz, corresponding to the spectral bandwidth of the F-band unitraveling-carrier photodiode (UTC-PD) used as a photomixer is described. The cw-terahertz generator could be applied as a terahertz clock and synthesizer for terahertz frequency metroloyg.

The factors influencing the coupling between the whispering gallery mode laser and the fiber around which it is formed are examined. The coupling between the laser and the dominant mode in the fiber is optimized by designing the dimension of mciroring, the eccentricity of the elliptical cross section and the material contrast between fiber and microring.

A nonperturbative approach based on the Kramers-Henneberger translation transformation is verified to be useful for carriers in semiconductor nanostructures under intense laser fields. The rapid coalescence of the energy levels with the increase in laser-dressing parameter ([[alpha].sub.0]) has increased the possibility of controlling the population inversion in quantum well lasers operating in the optical pumping scheme.

Monte Carlo transport simulation is used for analyzing the spectral gain for different terahertz quantum cascade laser structures by considering bound-to-continuum as well as resonant phonon depopulation designs. The temperature dependent gain broadening and the effect of the individual scattering mechanisms, such as electron-electron, impurity and interface roughness scattering are examined.

The design and fabrication of photonic crystal (PhC) based resonators for terahertz quantum-cascade laser with a gain maximum at 2.7 MHz is described. The devices are shown to be lasing in the bandgaps or at high-symmetry points of the PhC, depending on the period, and they have helped in tuning the emission of the lasers in the range of a few hundred gigahertz

Continuous wave and tunable laser operation is shown at room temperature with single crystals of Tm-doped NaLu[(W[O.sub.4]).sub.2]. Low temperature spectroscopy and energy level simulation methods have shown that energy levels and spectroscopic properties of [Tm.sup.3+] are compatible with the [S.sub.4] site symmetry.

Byline: M. Rohde Laser-supported processes can be used to modify the electrical and thermal properties of ceramic substrates locally. These processes are characterised by a strong thermal interaction between the laser beam and the ceramic surface. This interaction leads to localised melting. During the dynamic melting process, an additive material is injected into the melt pool in order to modify the physical properties. The heat and mass transfer during this dynamic melting and solidification process has been studied numerically in order to identify the dominating process parameters. Simulation tools based on a finite volume method have been developed to describe the heat transfer, fluid flow and phase change during the melting and solidification of the ceramic. The results of the calculation have been validated against experimental results.

Byline: T. Markovits, J. Takacs, A. Szilagyi, W. Xiufeng This paper presents an online method to measure the temperature and the deformations versus time during the laser bending of sheet materials. To measure the temperature and the deformations, an Infrared Thermovision System and a Deformation Amplifier System were used, respectively. In the experiments, two different types of steel were investigated the C45 and St14 in case of different sheet thicknesses. In the experiment results, the complex changing of the bending angle was measured in the range of laser power below 100 W. These results show the effect of the material, the thickness and the laser power on the temperature distribution and the bending angle. With this complex method, it was possible to relate the deformation and thermal data during the laser treatment. These data give suitable parameters for creating a model, which describes more precisely the laser bending process.

The design and simulation of a GaAs-based quantum cascade laser (QCL) emitting at 6.7 [micro]m is described. Monte Carlo simulation has shown that the proposed QCL has achieved room-temperature lasing at a threshold-current density of 14 kA/[cm.sup.2].

A new control scheme for quantum dynamics control of multilevel system based on effective decomposition by intense CW lasers is presented. The new scheme is found to be effective even for population dynamics control, as it suppresses the relaxation processes.

A simple quasianalytical formalism for static polarization-resolved light-current characteristic of dual polarization mode vertical-cavity surface-emitting lasers (VCSELs) under optical injection is presented. Dynamics of optical-injection-induced polarization switching are analyzed and simple analytical estimates for the polarization switching time are obtained.

Spectrally resolved spontaneous emission patterns of oxide-confined vertical-cavity surface-emitting lasers under the subthreshold condition were investigated. They show clear and stable Hermite-Gaussian modes and high-order Laguerre-Gaussian modes associated with a distinct spectrum.

A technique to measure the dynamic laws linewidth continuously within a laser pulse of 30 ns to several mus is presented. This technique can be used with any available single-mode quantum cascade laser in a wavelength range of 3 to 23 micrometer that corresponds to the working range of the detector.