The coherent combining of two Nd:YVO4 lasers has been demonstrated by use of a modified Michelson cavity. When the output power is 0.43W for the first channel laser, and 0.46W for the second channel laser, the combined output power of 0.83W is measured, which corresponded to a combining efficiency of more than 90%. When the output power is 0.89W for the first channel laser and 0.93W for the second channel laser at the maximum pump power, a combined output power of 1.6W is obtained. Moreover, the beam quality and coherent combining efficiency almost remain undecreased with the pump power. In addition, the environmental perturbations don't affect the beam quality and output power, and it has the potential for scaling to much higher output power by coherent combining of multiple lasers with this configuration.
KEYWORDS: Cladding, Fiber lasers, High power lasers, Mirrors, Photonic crystal fibers, Near field optics, Near field, Collimation, Laser crystals, Physics
A high power double-clad ytterbium-doped large-mode-area photonic crystal fibre (LMA PCF) laser was demonstrated using a unique Fabry-Perot (F-P) configuration. A Continuous-wave output power of 50 W at ~1.04 μm with a slope efficiency of 76.3% was obtained. Single transverse mode operation is achieved without any thermal-optical problems. This laser has the potential for scaling to much higher output power.
A novel method for the fabrication of continuous micro-optical components is presented in this paper. It employs a computer controlled spatial-light-modulator (SLM) as a switchable projection mask and silver-halide sensitized gelatin (SHSG) as recording material. By etching SHSG with enzyme solution, the micro-optical components with relief modulation can be generated through special processing procedures. The principles of digital SLM-based lithography and enzyme etching SHSG are discussed in detail, and microlens arrays, micro axicon-lens arrays and gratings with good profile were achieved. This method is simple, cheap and the aberration in processing procedures can be in-situ corrected in the step of designing mask, so it is a practical method to fabricate continuous profile for low-volume production.
Thermally induced rupture of a nonlinear crystal is the primary limiting factor to the attainment of High average power (HAP) in an optical parametric amplifier (OPA). In this paper, HAP scaling behavior in an OPA is addressed in detail by combining thermally induced phase mismatching with thermally induced rupture. Expressions for thermally induced stress are derived and analyzed that can give directions for a HAP-OPA design. When an OPA generates the maximum average output power, the dependence of flaw size on thermo optical material parameters of nonlinear crystals is obtained that is very useful for surface processing, material selecting, properties improving of a nonlinear crystal and new HAP nonlinear crystals developing.
An optimized coding gray-tone mask method with multi-parameters is presented in this paper. Precise calculations, which are performed on the dead area in the backward reflection of the pyramid prism, demonstrate that the fringe error caused by the coding gray-tone mask has little affect on the performance of the pyramid prisms. This not only greatly reduce the resolution requirement of the coding gray-tone mask, but also reduce the errors produced by the exposure
process. A satisfying simulation result is obtained with the designed coding gray-tone mask.
In this paper a new method has been developed for fabricating micro-optical element by exposing silver-halide sensitized gelatin (SHSG) through real-time mask and etching SHSG with enzyme solution. The principle of etching SHSG with enzyme solution is given in detail and the optimum technique parameters of this process are presented, furthermore the theoretical analysis and solving scheme for the nonlinearities which come from the absorption of light energy by film are given. It is experimentally obtained a good linear relationship in a range of 4µm deep. At last, the micro-cylindrical lens and micro axicon array are achieved by experiment, and the results are evaluated for experiments by stylus profiling instrument and interference microscope.
A new method is presented to encode and decode images with computer-generated hologram of fractional Fourier transform. The fractional Fourier transform computer-generated holograms (FRT-CGH) of several objects with different orders are respectively recorded on one holographic plate. In order to reconstruct images of the objects, several fractional Fourier transform systems of certain orders are needed. This method is agile and convenient on design and fabrication. It can be encoded and decoded either by numerical method or by optical method. Because of its particularity of image reconstruction, FRT-CGH is regarded as a new optical security system and may be widely used in the future.
A new technique to fabricate arbitrarily shaped microstructures by using LCD (liquid crystal display) real- time mask is reported in this paper. Its principle and design method are explained. Based on partial coherent imaging theory, the process to fabricate micro-axicon array and zigzag grating has been simulated. The experiment using a color LCD as real-time mask has been set up. Micro-axicon array and zigzag grating has been fabricated by the LCD real-time mask technique. The 3D surface relief structures were made on pan chromatic silver-halide sensitized gelatin (Kodak-131) with trypsinase etching. The pitch size of zigzag grating is 46.26micrometers . The caliber of axicon is 118.7micrometers , and the etching depth is 1.332micrometers .
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