Virtual Journal of Laser

Publication year: 2010
Source: Optics & Laser Technology, In Press, Corrected Proof, Available online 29 July 2010
M., Hoseinpour Gollo , S.M., Mahdavian , H., Moslemi Naeini
In recent years, laser application has been introduced for bending and forming as new processes in manufacturing. The capability of laser bending demands more studies to recognize parameters influencing bending angle of sheet metals. In this study the effects of parameters such as material, laser power, beam diameter, scan velocity, sheet thickness, pass number and pulse duration on bending angle were studied by FEM initially and then followed by experiments. Furthermore, the Taguchi experimental design method was employed to pin point parameters, which significantly affect the bending process of laser bending of St12 and 304 alloy steels, which have a...

Publication year: 2010
Source: Optics & Laser Technology, In Press, Corrected Proof, Available online 24 July 2010
Ruipin, Chen , Yongzhou, Ni , XiuXiang, Chu
The dynamic properties of cos-Gaussian beams in the presence of Kerr nonlinearity are investigated analytically and numerically using the nonlinear Schrödinger equation (NLS). Based on the moments method, evolution of a cos-Gaussian beam width in the root-mean-square (RMS) sense is obtained analytically. The beam propagation factors and the critical powers of the cos-Gaussian beams with a uniform wavefront are calculated. Using numerical simulation, it is found that although the RMS beam width broadens, the central parts of the beam give rise to an initial radial compression and a significant redistribution during propagation. The partial collapse of central parts of the...

Publication year: 2010
Source: Optics & Laser Technology, In Press, Corrected Proof, Available online 23 July 2010
Yonggen, Xu , Yude, Li , Bin, Zhang , Ting, Feng , Yi, Qiu
The axisymmetrical structural traveling wave cavity (ASSC) CO2 laser is introduced based on the propagation theory of the standing wave cavity CO2 laser. Then the propagation characteristics of the elliptically polarized Gaussian beam are studied in detail. The transforms of the coordinate were used to solve the near field distributions of the output laser beams. The numerical calculations show that the combination of the output beams in the near field can be fulfilled. The diminutive ASSC CO2 laser can be applied into the laser gyro and the measure of the angular velocity.

Publication year: 2010
Source: Optics & Laser Technology, In Press, Corrected Proof, Available online 21 July 2010
Pan-Pan, Niu , Xiang-Yang, Wang , Hai-Bo, Jin , Ming-Yu, Lu
Desynchronization attacks are among the most difficult attacks to resist, for it can desynchronize the location of the watermark and hence cause incorrect watermark detection. The design of an image watermarking scheme that is robust against desynchronization attacks is challenging. Based on a multi-scale SIFT (scale invariant feature transform) detector and Bandelet transform theory, we propose a new content based image watermarking algorithm with good visual quality and reasonable resistance toward desynchronization attacks. Firstly, the stable image feature points are extracted from the original host by using the multi-scale SIFT detector, and the local feature regions (LFRs) are constructed adaptively...

Publication year: 2010
Source: Optics & Laser Technology, In Press, Corrected Proof, Available online 20 July 2010
Nafissa, Khanafi-Benghalem , Kamel, Benghalem
In this present paper, the optical bistability in a circular laser containing a saturable absorber LSA for inhomogeneous broadening is studied. A simple mathematical model was developed to describe the action of this type of laser in a circular resonator under two conditions, when the spontaneous emission is neglected or included in the cavity. For both of these two cases, the coefficient of saturation was considered to be equal or different to unity (ζ=1 or ζ≠1). The photons intensities Qj were determined as function of the pumping rate σ0 of the active medium and analyzed the linear stability of the...

Publication year: 2010
Source: Optics & Laser Technology, In Press, Corrected Proof, Available online 17 July 2010
C., Weiss , S., Aghabi
The automation of CO2 laser output power measurement is discussed in this paper as a function of the absorber gas pressure in a cell located inside or outside the laser cavity. A manually tunable laser was used which can be operated in one of about 44 different laser lines aligned by the user and registered respectively by the acquisition program for further analysis.The voltages representing the absorber gas pressure and the output power were very small (a few hundred μV), therefore a proper voltage amplification circuit was designed to amplify the analog outputs of both the pressure meter and the...

Publication year: 2010
Source: Optics & Laser Technology, In Press, Corrected Proof, Available online 16 July 2010
Lianghong, Yan , Haibing, Lv , Chengcheng, Wang , Xiaodong, Yuan
A simple method of preparing hydro-oleophobic anitreflective films with high laser-damage threshold is reported in this article. By adding fluoroalkylsilanes (FAS) into reactant mixture as a co-precursor, FAS modified SiO2 was obtained under base catalyzed hydrolysis and condensation of tetraethoxysilane. The dip-coating films were deposited on two sides of fused silica substrates.The experimental results on the effect of adding fluoroalkylsilanes (FAS) as a co-precursor on the hydro-oleophobicity and optical properties of tetraethoxysilane (TEOS) based silica AR films, are reported. The hydro-oleophobicity of the films was tested by the contact angle measurements and the highest water contact angle of 136° and...

Publication year: 2010
Source: Optics & Laser Technology, In Press, Corrected Proof, Available online 16 July 2010
Tingting, Tang , Fushen, Chen , Bao, Sun
We study tunneling modes in a one-dimensional photonic crystal (1DPC) with multilayered periodic structures containing dispersive anisotropic single-negative (ASNG; permittivity- or permeability-negative) metamaterials. A defect layer is introduced into the proposed structure, and some unusual properties are found in contrast with that of a tunneling mode in PCs with isotropic single-negative (SNG) gaps.

Publication year: 2010
Source: Optics & Laser Technology, In Press, Corrected Proof, Available online 16 July 2010
Chris, Brown

Publication year: 2010
Source: Optics & Laser Technology, In Press, Corrected Proof, Available online 17 July 2010
Gangxian, Zhu , Dichen, Li , Anfeng, Zhang , Yiping, Tang
To investigate the influencing rule of deposited layer’s shape on coaxial powder feeding flow field in the metal forming process, gas–solid two-phase flow theory is used to analyze effect of deposited layers on powder concentration distribution and variation of focus distance from nozzle outlet to convergence point (the center of the convergent zone). Different height and width parameters of deposited layers were chosen to calculate the powder concentration distribution, consequently, and also their effect on additive height of single-trace cladding layer was studied by experimental investigations. The numerical results are in good agreement with experimental observations. The results indicated that...