Virtual Journal of Laser

Publication year: 2010
Source: Optics & Laser Technology, In Press, Corrected Proof, Available online 23 December 2010
Jie, Yu , Chongfeng, Guo , Zhaoyu, Ren , Jintao, Bai
Eu2+ activated Ca5(PO4)3Cl blue-emitting phosphors were prepared by the conventional solid state method using CaCl2 as the chlorine source and H3BO3 as flux. The structure and luminescent properties of phosphors depend on the concentrations of Eu2+, the amount of CaCl2 and the usage of the H3BO3 flux were investigated systematically. Eu2+ and Mn2+ Co-doped Ca5(PO4)3Cl with blue and orange double-band emissions were also researched based on the optimal composition and synthesis conditions. The energy transfer between Eu2+ and Mn2+ was found in the phosphor Ca5(PO4)3Cl:Eu2+, Mn2+, and the Co-doped phosphor can be efficiently excited by near-UV light, indicating that the...

Publication year: 2010
Source: Optics & Laser Technology, In Press, Corrected Proof, Available online 18 December 2010
S.Z., Shuja , B.S., Yilbas
The flow field developed in the laser produced melt pool is investigated and the influence of the Marangoni effect on temperature field is examined. The experiment is carried out to trace the solidified melt pool geometry and the heating is simulated in line with the experimental conditions to predict the melt size in the irradiated region. In the simulations, the control volume approach is used incorporating the Marangoni effect. The enthalpy-porosity method is adopted to account for the phase change in the irradiated region. The study is extended to include the influence of the laser intensity parameter (β) on temperature...

Publication year: 2010
Source: Optics & Laser Technology, In Press, Corrected Proof, Available online 16 December 2010
Yuanguang, Wang , Yixin, Zhang , Jianyu, Wang , Jianjun, Jia
Nonclassical polarization properties of a quantum field propagating through non-Kolmogorov turbulence are studied in a turbulent atmosphere paraxial channel. The analytic equation for the quantum degree of polarization of linearly polarized light is obtained. It is shown by numerical simulation that the polarization fluctuations of the quantum field are a function of the turbulent strength, the photon number, the propagation distance, the fractal constant α and the coherence length ρ0.

Publication year: 2010
Source: Optics & Laser Technology, In Press, Corrected Proof, Available online 13 December 2010
I.Y., Khalfallah , M.N., Rahoma , J.H., Abboud , K.Y., Benyounis
Surface modification of AISI316 stainless steel by laser melting was investigated experimentally using 2 and 4kW laser power emitted from a continuous wave CO2 laser at different specimen scanning speeds ranged from 300 to 1500mm/min. Also, an investigation is reported of the introduction of carbon into the same material by means of laser surface alloying, which involves pre-coating the specimen surfaces with graphite powder followed by laser melting. The aim of these treatments is to enhance corrosion resistance by the rapid solidification associated with laser melting and also to increase surface hardness without affecting the bulk properties by increasing the...

Publication year: 2010
Source: Optics & Laser Technology, In Press, Corrected Proof, Available online 13 December 2010
F.A., Al-Agel
Bulk Ge20Se80−xTlx (x ranging from 0 to 15at%) chalcogenide glasses were prepared by conventional melt quenching technique. Thin films of these compositions were prepared by thermal evaporation, on glass and Si wafer substrates at a base pressure of 10−6Torr. X-ray diffraction studies were performed to investigate the structure of the thin films. The absence of any sharp peaks in the X-ray diffractogram confirms that the films are amorphous in nature. The optical constants (absorption coefficient, optical band gap, extinction coefficient and refractive index) of Ge20Se80−xTlx thin films are determined by absorption and reflectance measurements in a wavelength range of 400–900nm....

Publication year: 2010
Source: Optics & Laser Technology, In Press, Corrected Proof, Available online 9 December 2010
Suqin, Yin , Bin, Zhang , Youquan, Dan
When high-power annular laser beams produced by the unstable resonator pass through the volume Bragg grating (VBG), absorption of light in the VBG will induce a temperature increment, resulting in changes in surface distortion. Considering that the surface distortion of the grating induces index and period differences, the scalar wave equations for the annular laser beams propagating in the VBG have been solved numerically and iteratively using finite-difference and sparse matrix methods. The variation in intensity distributions, the total power reflection coefficient, and the power in the bucket (PIB) for the annular laser beams passing through the reflection VBG with...

Publication year: 2010
Source: Optics & Laser Technology, In Press, Corrected Proof, Available online 30 November 2010
Xiao Hong, Sun , Xiao Ming, Tao
Single-prism systems are used to fabricate electrically switchable Photonic Crystal (PhC) structures in Polymer Dispersed Liquid Crystal (PDLC) films. The optical configuration is simple, stable and repeatable. A good agreement between theoretical and experimental results is obtained for the PhC structures. Hexagonal far-field diffraction patterns and electrical switching characteristics are also investigated. The smallest droplets of liquid crystals are 10nm in diameter. The switching voltage can be decreased to 13.3V/μm.

Publication year: 2010
Source: Optics & Laser Technology, In Press, Corrected Proof, Available online 26 November 2010
Fei, Wang
A stable multiwavelength mode-locked semiconductor fiber ring laser incorporating a fiber Mach-Zehnder interferometer (MZI) filter was proposed and experimentally demonstrated. A semiconductor optical amplifier (SOA) serves as an optically controlled mode-locking element due to gain exhaustion caused by external injected optical pulses. Another SOA severs as a constant-gain medium. A fiber MZI filter with a temperature control is incorporated into the fiber ring cavity to acquire a stable and tunable multiwavelength oscillation. Twelve wavelengths are synchronously mode-locked at 10GHz, pulse width of mode-locked pulse are about 30ps. Proposed multiwavelength mode-locked semiconductor fiber ring laser has some distinct advantages, such as...

Publication year: 2010
Source: Optics & Laser Technology, In Press, Corrected Proof, Available online 26 November 2010
B.S., Yilbas , A.F.M, Arif
In laser cutting of sheet metals, thermal stresses are developed in the region of the cutting section. Depending on the cutting conditions and substrate material properties, the thermal stress levels can attain high values. In the present study, thermal stress developed in the region of the laser cut edges is modeled and temperature as well as stress fields are predicted. Temperature predictions are validated through the experimental results. It was found that the temporal variation of the maximum temperature along y-axis follows the laser heating source. However, temporal variation of von-Mises stress deviates slightly from the temporal variation of temperature...

Publication year: 2010
Source: Optics & Laser Technology, In Press, Corrected Proof, Available online 26 November 2010
D.E., Ceballos-Herrera , I., Torres-Gomez , A., Martinez-Rios , G., Anzueto-Sanchez , Y., Barmenkov
In this paper, we propose and demonstrate a versatile and simple single-, dual- and three-wavelength switchable ytterbium-doped fiber laser using the intracavity induced-loss generated by a mechanically induced long-period grating (MLPFG) in a holey fiber. The laser net gain in the cavity is reshaped through the MLPFG by adjusting the twist rate and the pressure of the holey fiber in the long-period grating. In this way, the twist response of the MLPFG enables the laser to switch between the single-, dual-, and three-wavelength operations and the tuning of the simultaneous two- and three-wavelengths. These results are of great interest in...