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Nonlinear Optical Properties Of Hybrid Materials And Nanostructure Induced By Femtosecond Laser

Posted on:2010-06-19Degree:DoctorType:Dissertation
Country:ChinaCandidate:Q YangFull Text:PDF
GTID:1118360302465214Subject:Optics
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The femtosecond laser provides us an advanced means for ultrafast phenomenon owning to it's characteristics of ultra-short duration and super-high peak power , and provides us a brand-new method for the fabrication of micro/nano-structure. To meet the demands of the rapidly growing of high-speed and high load-carry-capacity information technology, all-optical switches, optical storage and all-optical logical gates play the key roles in the information technology which have attracted intense attentions. Thus, it is very important to understand the interaction mechanism betweet the femotsecond laser and nonlinear optical materials.Femtosecond laser induced optical Kerr effects technique is one of the key methods to study the characteristics of nonlinear optical materials. In the present thesis, the ultrafast nonlinear optical properties of Bi2-O3-B2O3-SiO2 oxide glasses, organic-inorganic hybrids materials based on lead phthalocyanine and C60 were investigated using 30-fs pulse laser, and compared it with the previous study by 200-fs pulse laser, Research results obtained are as follows:.The response time of CS2 molecule re-tropism was measured to be about 1. 6ps by the experiment of femtosecond laser induced optical Kerr effects using 30-fs pulse laser, and the dependence of Kerr signals on the polarization angle between pump and probe beams showed that the Kerr signals of CS2 induced by 30-fs pulse laser arose mainly from the photoinduced birefringence effect.The nonlinear response time of PbPc was measured to be about 85fs, which was the fastest response observed in organic-inorganic hybrids materials so far. And the response time Bi2O3-doped glassed was measured to be less than 90fs, which was the fastest response observed in nonlinear optical glasses. Measurements of the dependence of Kerr signals on the polarization angle between pump and probe beams showed that the Kerr signal induce by 30-fs pulse laser in Bi2O3-doped glasses, PbPc and C60 were dominated by the optical Kerr effect due to photoinduced birefringence effect, which was different from photoinduced transient grating effect by 200-fs pulse laser. These studies shows that shorter laser pulses induced optical Kerr effect could reflect the nonlinear optical properties of the materials more exactly, which can provide a new ideas for study of the interaction of ultrashort pulses and nonlinear optical materials.We have performed a detailed study on the micro-gratings encoded on the surface of Au-Cr thin film using two-beam interference of femtosecond pulses with the durations from 25 fs to 70 fs both theoretically and experimentally. The experimental results and numeral analysis indicated that the duration of laser pulses in this time domain will influence the qualities of encoded gratings significantly.Periodic surface nanostructures induced by femtosecong laser on polycrystalline ZnO were presented. The dependence of the morphology of the periodic structures on the experiment conditions such as laser fluence, pulse number and laser polarization, were studied by Scanning electronic microscope (SEM). By translating the sample line-by-line with appropriate irradiation conditions, grating-like nanostructures were fabricated on polycrystalline ZnO surface. For shorter pulse durations, process was implemented under the condition that the laser influence was slightly exceeded the ablation threshold, which was helpful to produce microstructures with fine resolution. This is favorable to implement fine surface processing and modification on various materials, especially for intractable materials.
Keywords/Search Tags:Ultrafast nonlinear optical properties, Hybrid materials, Kerr effect, Self-diffraction effect, ZnO, Nanostrucre
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