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Study of the Formation of a Intense Filamentation Based on Spatial Modulation of Interference Effect of Ultraviolet Femtosecond Pulses

Author: ZhangYiSan
Tutor: DingLiangEn
School: East China Normal University
Course: Optics
Keywords: UV femtosecond laser Light wire Coherent Field Spatial modulation Plasma grating Fluorescence intensity
CLC: TN241
Type: Master's thesis
Year: 2011
Downloads: 18
Quote: 0
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Abstract


Femtosecond laser plasma filaments effects can provide a powerful means of research and potential applications for the field of atomic and molecular physics, precision spectroscopy, laser chemistry and laser biology. Ultraviolet light silk band effect with lower photoionization threshold, plasma high yield, strong nonlinear effects gradually become a strong laser field of physics research hotspot. With the improvement of the UV laser single pulse energy, due to the irregular spatial distribution of the light field, the laser interacts with the medium in the transmission process unevenness, especially the occurrence of light wire, resulting in the collapse of the loss of energy and light wire. Irregular achieve optical wire process control can be improved through the modulation of the light field space of the laser beam spot space. Coherent spatial modulation of the non-collinear UV femtosecond laser light field of the paper as the basic method, ultraviolet coherent light silk optical field effect its manipulation. The work carried out as follows: 1, non-collinear double beam UV femtosecond laser spatial coherence and modulation effects of the light field. When the wavelength of the incident laser beam is constant, becomes larger as the angle of the two beams of coherent light, a pitch of the interference fringes in the coherent area was gradually narrowed, the number of stripes would gradually increase. In addition, we found that through the spatial coherence of the non-collinear dual-beam laser, the original unevenness of the laser spot will rules stripes, to achieve the purpose of improving the manipulation of the process of the light silk. 2, dual ultraviolet beam of coherent the plasma grating optical field generation and observation. When femtosecond ultraviolet coherent light field space plasma grating formation through microscopic imaging, we observed interference fringes of the the ion recombination bright white. Compared with the ionic complex fluorescence intensity of the single beam of ultraviolet wire, plasma fluorescence intensity within the grating region has been significantly enhanced, and is enhanced with the increase of the incident laser energy. Experiments, we found that the spectral width of the UV laser pulse after coherent broadening 4m, 2 times before coherent. Baseband light further enhanced plasma grating. We will base frequency light into plasma grating light silk and plasma grating formed by the successor to the base frequency laser interaction. When fundamental and two beams of ultraviolet coherent light synchronization fluorescence within the interaction region will be significantly enhanced role, about ultraviolet coherent the plasma grating light field fluorescence radiation 8 times. This light wire be plasma grating fluorescence light generated by subsequent baseband complementary role.

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