Distortion of beam shape by a rotating double-prism wide-angle laser beam scanner

We describe the rigorous results of a wide-angle laser beam scanner, obtained with the help of the vector refraction theory. Using the rigorous results, the distortion of the beam shape is discussed. The distortion to the beam varies with the different relative angles of double prisms. The scanner expands the beam in some directions while it contracts the beam in other directions. According to the conservation of energy, the distribution of the laser intensity is changed as well. (c) 2006 Society of Photo-Optical Instrumentation Engineers.

The effect of the rotating double-prism wide-angle laser beam scanner on the beam shape

In this paper, we describe a wide-angle laser beam scanner and the rigorous result of the wide-angle laser beam scanner was obtained with the help of the vector refraction theory. Using the rigorous results, the distortion of the beam shape was discussed. The distortion of the beam shape is varying with the different relative angles of the double prisms. According to the conservation of the energy, the distribution of the laser intensity is changed too. (c) 2005 Elsevier GmbH. All rights reserved.

Distortion of beam shape by a rotating double-prism wide-angle laser beam scanner

We describe the rigorous results of a wide-angle laser beam scanner, obtained with the help of the vector refraction theory. Using the rigorous results, the distortion of the beam shape is discussed. The distortion to the beam varies with the different relative angles of double prisms. The scanner expands the beam in some directions while it contracts the beam in other directions. According to the conservation of energy, the distribution of the laser intensity is changed as well. (c) 2006 Society of Photo-Optical Instrumentation Engineers.

Laser beam shaping system with a radial birefringent filter

Reshaping of a Gaussian laser beam into a uniform or other intensity distribution is required for various applications. The laser beam shaping system with a radial birefringent filter is presented in this paper. With such a system the Gaussian beams can be transformed into uniform or annular beams. The theory and simulation of the proposed systems are described in detail. The primary advantage of such a system is that the out beam pro. le can be tunable with the rotation of the radial birefringent element.

Technique for diagnosing x-ray laser beam quality by use of the moire signal

We present what we believe is a novel technique based on the moire effect for fully diagnosing the beam quality of an x-ray laser. Using Fresnel diffraction theory, we investigated the intensity profile of the moire pattern when a general paraxial beam illuminates a pair of Ronchi gratings in the quasi-far field. Two formulas were derived to determine the beam quality factor M-2 and the effective radius of curvature R-e from the moire pattern. On the basis of the results, the far-field divergence, the waist location, and the radius can be calculated further. Finally, we verified the approach by use of numerical simulation. (C) 1999 Optical Society of America [S0740-3232(99)01502-1].

Laser beam automatic alignment in multipass amplifier

A laser beam automatic alignment system is applied in a multipass amplifier of the SG-III prototype laser. Considering the requirements of the SG-III prototype facility, by combining the general techniques of the laser beam automatic alignment system, according to the image relayed of the pinholes in the spatial filter, and utilizing the optical position and the spatial distribution of the four pinholes of the main spatial filter in the multipass amplifier of the SG-III prototype, a reasonable and optimized scheme for automatic aligning multipass beam paths is presented. It is demonstrated on the multipass amplifier experimental system. (C) 2004 Society of Photo-Optical Instrumentation Engineers.

Self-organized microvoid array perpendicular to the femtosecond laser beam in CaF2 crystals

Microvoid arrays were self-organized when femtosecond laser beam was tightly focused at a fixed point inside CaF2 crystal sample. Except void array grown below the focal point which had been reported before, we found another void array grown vertical to the laser propagation direction. This result has potential application in the fabrication of integrated micro-optic elements and photonic crystals. The possible mechanism of the phenomenon was proposed and verified experimentally.

Characteristics of the conductive polyimide film surfaces induced by ultraviolet laser beam

A conducting layer with the conductivity of 1.2 Omega(-1)cm(-1) stripped in a solvent from KrF-laser-irradiated polyimide thin film is taken as a sample to determine the microstructure of the conducting layer. Fourier-transform infrared and X-ray photoelectron spectroscopies show the formation of the carbon-rich clusters after irradiation. The element analysis gives the atomic ratio of C:H:N:O for the carbon-rich cluster as 60:20:3:1. Wide-angle X-ray diffraction indicates that the conducting layer is mainly amorphous carbon with a small amount of the short-range ordered carbon-rich clusters. This study suggests a structural model with three-layer carbon sheets linked together in a random fashion for the short-range ordered carbon-rich clusters. The interplanar spacing is 3.87 Angstrom and the layer diameter 25 Angstrom. The transport model of variable-range hopping in three dimensions is used to explain the conducting behavior of the conducting layer. In our case, the short-range ordered carbon-rich clusters are assumed to be conducting islands dispersed in the amorphous carbon-rich cluster matrix.

Nano-modification inside transparent materials by femtosecond laser single beam

Periodic nanostructures along the polarization direction of light are observed inside silica glasses and tellurium dioxide single crystal after irradiation by a focused single femtosecond laser beam. Backscattering electron images of the irradiated spot inside silica glass reveal a periodic structure of stripe-like regions of similar to 20 nm width with a low oxygen concentration. In the case of the tellurium dioxide single crystal, secondary electron images within the focal spot show the formation of a periodic structure of voids with 30 nm width. Oxygen defects in a silica glass and voids in a tellurium dioxide single crystal are aligned perpendicular to the laser polarization direction. These are the smallest nanostructures below the diffraction limit of light, which are formed inside transparent materials. The phenomenon is interpreted in terms of interference between the incident light field and the electric field of electron plasma wave generated in the bulk of material.

Electron beam and laser testing on the novel stripixel detectors

The novel Si stripixel detector, developed at BNL (Brookhaven National Laboratory), has been applied in the development of a prototype Si strip detector system for the PHENIX Upgrade at RHIC. The Si stripixel detector can generate X-Y two-dimensional (2D) position sensitivity with single-sided processing and readout. Test stripixel detectors with pitches of 85 and 560 mu m have been subjected to the electron beam test in a SEM set-up, and to the laser beam test in a lab test fixture with an X-Y-Z table for laser scanning. Test results have shown that the X and Y strips are well isolated from each other, and 2D position sensitivity has been well demonstrated in the novel stripixel detectors. (c) 2005 Elsevier B.V. All rights reserved.

Numerical simulation of an adaptive optics system with laser propagation in the atmosphere

A comprehensive model of laser propagation in the atmosphere with a complete adaptive optics (AO) system for phase compensation is presented, and a corresponding computer program is compiled. A direct wave-front gradient control method is used to reconstruct the wave-front phase. With the long-exposure Strehl ratio as the evaluation parameter, a numerical simulation of an AO system in a stationary state with the atmospheric propagation of a laser beam was conducted. It was found that for certain conditions the phase screen that describes turbulence in the atmosphere might not be isotropic. Numerical experiments show that the computational results in imaging of lenses by means of the fast Fourier transform (FFT) method agree well with those computed by means of an integration method. However, the computer time required for the FFT method is 1 order of magnitude less than that of the integration method. Phase tailoring of the calculated phase is presented as a means to solve the problem that variance of the calculated residual phase does not correspond to the correction effectiveness of an AO system. It is found for the first time to our knowledge that for a constant delay time of an AO system, when the lateral wind speed exceeds a threshold, the compensation effectiveness of an AO system is better than that of complete phase conjugation. This finding indicates that the better compensation capability of an AO system does not mean better correction effectiveness. (C) 2000 Optical Society of America.

Research on Dynamic Micro-Deformation under Laser Point Source

The dynamic micro-deformation of the specimen under laser point source is measured using a laser beam reflex amplifier system and numerically simulated by Msc.Marc software. Compared with experimental result and calculated result, the final deformation direction of the specimen depends on the result of the thermal strain and the phase transformation strain cooperation, away from the laser beam or towards the laser beam, the final deformation angle depends on temperature gradient in the thickness direction and the geometry constraint of the specimen. The conclusion lays the foundation for further research on the mechanism of laser bending. At the same time, it is proposed that the model of calculation based on classical Fourier heat transfer theory cannot be enough to simulate the dynamic micro-deformation of the specimen under laser point source, the model of calculation should be modified in the future.