(Ti,Al)N Film On Normalized T8 Carbon Tool Steel Prepared By Pulsed High Energy Density Plasma Technique

Under optimized operating parameters, a hard and wear resistant ( Ti,Al)N film is prepared on a normalized T8 carbon tool steel substrate by using pulsed high energy density plasma technique. Microstructure and composition of the film are analysed by x-ray diffraction, x-ray photoelectron spectroscopy, Auger electron spectroscopy and scanning electron microscopy. Hardness profile and tribological properties of the film are tested with nano-indenter and ring-on-ring wear tester, respectively. The tested results show that the microstructure of the film is dense and uniform and is mainly composed of ( Ti,Al)N and AlN hard phases. A wide transition interface exists between the film and the normalized T8 carbon tool steel substrate. Thickness of the film is about 1000 nm and mean hardness value of the film is about 26GPa. Under dry sliding wear test conditions, relative wear resistance of the ( Ti,Al)N film is approximately 9 times higher than that of the hardened T8 carbon tool steel reference sample. Meanwhile, the ( Ti,Al)N film has low and stable friction coefficient compared with the hardened T8 carbon tool steel reference sample.

High-efficiency volume hologram recording with a pulsed signal beam

We present an efficient photorefractive volume hologram recording technique with a pulsed signal beam and continuous reference-beam illumination. The grating envelope can be simply controlled by manipulation of the duty cycle of the signal beam. Thus, for any grating coupling strength and different initial reference-signal intensity ratios, the diffraction efficiency can be maximized with this technique and can be greatly increased in comparison with that of the conventional recording technique. (C) 1998 Optical Society of America.

Wavefront measurement of double-clad pulsed ytterbium fiber laser

Because of high efficiencies, compact structure, and excellent heat dissipation, high-power fiber lasers are extremely useful for applications such as cutting, welding, precision drilling, trimming, sensing, optical transmitter, material processing, micromachining, and so on. However, the wavefront of the double clad fiber laser doped with ytterbium is still unknown. In this paper, wavefront of a fiber laser is measured and the traditional Hartmann-shack wavefront sensing method is adopted. We measured a double clad fiber laser doped with ytterbium which produces pulse wave output at infrared wavelength. The wavefront shape and contour are reconstructed and the result shows that wavefront is slightly focused and not an ideal plane wavefront. Wavefront measurement of fiber laser will be useful to improving the lasers' performance and developing the coherent technique for its applications.

Intensity-moments characterization of general pulsed paraxial beams with the Wigner distribution function

On the basis of the space-time Wigner distribution function (STWDF), we use the matrix formalism to study the propagation laws for the intensity moments of quasi-monochromatic and polychromatic pulsed paraxial beams. The advantages of this approach are reviewed. Also, a least-squares fitting method for interpreting the physical meaning of the effective curvature matrix is described by means of the STWDF. Then the concept is extended to the higher-order situation, and what me believe is a novel technique for characterizing the beam phase is presented. (C) 1999 Optical Society of America [S0740-3232(99)001009-1].

Magnetic field modulated direct overwrite with pulsed laser irradiation for TbFeCo magneto-optical disks

WE have designed a dual-beam magneto-optical (MO) storage system to test the dynamic storage properties of MO disks. The characteristics of this dual-beam system are demonstrated. Magnetic field modulated direct overwrite, which is a promising technique for highspeed MO storage, is realized on TbFeCo MO disks with this dual-beam MO system. The effect of light intensity, magnetic field intensity, and linear velocity of the disk and the modulating frequency variation on carrier-to-noise ratio is investigated. (C) 1997 Society of Photo-Optical Instrumentation Engineers.

A compact diode-pumped injection seeded Nd : YAG laser with resonance-detection technique

A diode pumped injection seeded single-longitudinal-mode (SLM) Nd:YAG laser is achieved by using the resonance-detection technique in Q-switching operation. The pulsed oscillator laser uses a folded cavity to achieve compact construction. This system operates at 100 Hz and provides over 20 mJ/pulse of single-frequency 1064 nm output. The M-2 values of horizontal and vertical axes are 1.58 and 1.41, respectively. The probability of putting out single-longitudinal-mode pulses is 100%. The 355 nm laser output produced by frequency tripling has a linewidth less than 200 MHz. The laser can run over eight hours continually without mode hopping.

Welding of Al alloy plates using a novel high-average-power pulsed CO2 laser

A novel high-average-power pulsed CO2 laser with a unique electrode structure is presented. The operation of a 5-kW transverse-flow CO2 laser with the preionized pulse-train switched technique results in pulsation of the laser power, and the average laser power is about 5 kW. The characteristic of this technique is switching the preionized pulses into pulse trains so as to use the small preionized power (hundreds of watts) to control the large main-discharge power (tens of kilowatts). By this means, the cost and the complexity of the power supply are greatly reduced. The welding of LF2, LF21, LD2, and LY12 aluminum alloy plates has been successfully achieved using this laser. (c) 2005 Society of Photo-Optical Instrumentation Engineers.

Welding of Al alloy plates using a novel high-average-power pulsed CO2 laser

A novel high-average-power pulsed CO2 laser with a unique electrode structure is presented. The operation of a 5-kW transverse-flow CO2 laser with the preionized pulse-train switched technique results in pulsation of the laser power, and the average laser power is about 5 kW. The characteristic of this technique is switching the preionized pulses into pulse trains so as to use the small preionized power (hundreds of watts) to control the large main-discharge power (tens of kilowatts). By this means, the cost and the complexity of the power supply are greatly reduced. The welding of LF2, LF21, LD2, and LY12 aluminum alloy plates has been successfully achieved using this laser. (c) 2005 Society of Photo-Optical Instrumentation Engineers.

Growth and properties of ZnO thin film on beta-Ga2O3(100) substrate by pulsed laser deposition

Zinc oxide (ZnO) thin films were grown on the beta-Ga2O3 (100) substrate by pulsed laser deposition (PLD). X-ray diffraction (XRD) indicated that the ZnO films are c-axis oriented. The optical and electrical properties of the films were investigated. The room temperature Photoluminescence (PL) spectrum showed a near band emission at 3.28 eV with two deep level emissions. Optical absorption indicated a visible exciton absorption at room temperature. The as-grown films had good electrical properties with the resistivities as low as 0.02 Omega cm at room temperature. Thus, beta-Ga2O3 (100) substrate is shown to be a suitable substrate for fabricating ZnO film. (c) 2006 Elsevier B.V. All rights reserved.

Comparison of ZnO films grown on before- and after-vapor transport equilibration (VTE) LiAlO2 substrates by pulsed laser deposition (PLD)

About Phi 45 mm LiAlO2 single crystal was grown by Czochralski (Cz) technique. However, the full-width at half-maximum (FWHM) value was high to 116.9 arcsec. After three vapor transport equilibration (VTE) processes, we can obtain high-quality LiAlO2 slice with the FWHM value of 44.2 arcsec. ZnO films were fabricated on as-grown slices and after-VTE ones by pulsed laser deposition (PLD). It was found that ZnO films on the two slices have similar crystallinity, optical transmittance and optical band gap at room temperature. These results not only show that LAO substrate is suitable for ZnO growth, but also prove that the crystal quality of LAO substrate slightly affects the structural and optical properties of ZnO film.

Low temperature annealing effects on the structure and optical properties of ZnO films grown by pulsed laser deposition

ZnO thin films were deposited on glass substrates at room temperature (RT) similar to 500 degrees C by pulsed laser deposition (PLD) technique and then were annealed at 150-450 degrees C in air. The effects of annealing temperature on the microstructure and optical properties of the thin films deposited at each substrate temperature were investigated by XRD, SEM, transmittance spectra, and photoluminescence (PL). The results showed that the c-axis orientation of ZnO thin films was not destroyed by annealing treatments: the grain size increased and stress relaxed for the films deposited at 200-500 degrees C, and thin films densified for the films deposited at RT with increasing annealing temperature. The transmittance spectra indicated that E-g of thin films showed a decreased trend with annealing temperature. From the PL measurements, there was a general trend, that is UV emission enhanced with lower annealing temperature and disappeared at higher annealing temperature for the films deposited at 200-500 degrees C; no UV emission was observed for the films deposited at RT regardless of annealing treatment. Improvement of grain size and stoichiometric ratio with annealing temperature can be attributed to the enhancement of UV emission, but the adsorbed oxygen species on the surface and grain boundary of films are thought to contribute the annihilation of UV emission. It seems that annealing at lower temperature in air is an effective method to improve the UV emission for thin films deposited on glass substrate at substrate temperature above RT.

Crystallization of amorphous Si films by pulsed laser annealing and their structural characteristics

Nanocrystalline silicon (nc-Si) films were prepared by pulsed laser annealed crystallization of amorphous silicon (alpha-Si) films on SiO2-coated quartz or glass substrates. The effect of laser energy density on structural characteristics of nc-Si films was investigated. The Ni-induced crystallization of the a-Si films was also discussed. The surface morphology and microstructure of these films were characterized by scanning electron microscopy, high-resolution electron microscopy, atomic force microscopy and Raman scattering spectroscopy. The results show that not only can the alpha-Si films be crystallized by the laser annealing technique, but also the size of Si nanocrystallites can be controlled by varying the laser energy density. Their average size is about 4-6 nm. We present a surface tension and interface strain model used for describing the laser annealed crystallization of the alpha-Si films. The doping of Ni atoms may effectively reduce the threshold value of laser energy density to crystallize the alpha-Si films, and the flocculent-like Si nanostructures could be formed by Ni-induced crystallization of the alpha-Si films.

Structural properties of polycrystalline silicon films formed by pulsed rapid thermal processing

A novel pulsed rapid thermal processing (PRTP) method has been used for realizing solid-phese crystallization of amorphous silicon films prepared by plasma-enhanced chemical vapour deposit ion. The microstructure and surface morphology of the crystallized films were investigated using x-ray diffraction and atomic Force microscopy. The results indicate that PRTP is a suitable post-crystallization technique for fabricating large-area polycrystalline silicon films with good structural quality, such as large grain size, small lattice microstrain and smooth surface morphology on low-cost glass substrates.

Polycrystalline silicon films prepared by improved pulsed rapid thermal annealing

An improved pulsed rapid thermal annealing (PRTA) has been used for the solid-phase crystallization (SPC) of a-Si films prepared by PECVD. The SPC can be completed with time-temperature budgets such as 10 cycles of 60-s 550 degrees C thermal bias/1-s 850 degrees C thermal pulse. The microstructure and surface morphology of the crystallized films are investigated by X-ray diffraction (XRD). The results indicate that this PRTA is a suitable post-crystallization technique for fabricating large-area poly-Si films on low-cost substrate. (C) 2000 Elsevier Science B.V. All rights reserved.

Structural properties of polycrystalline silicon films formed by pulsed rapid thermal processing

A novel pulsed rapid thermal processing (PRTP) method has been used for realizing the solid-phase crystallization of amorphous silicon films prepared by PECVD. The microstructure and surface morphology of the crystallized films are investigated by X-ray diffraction (XRD) and atomic force microscopy (AFM). The results indicate that this PRTP is a suitable post-crystallization technique for fabricating large-area polycrystalline silicon films with good structural qualities such as large grain size, small lattice microstain and smooth surface morphology on low-cost substrate.