【作者】 郭驾宇；

【导师】 钱国栋； 王民权；

【作者基本信息】 浙江大学 ， 材料学， 2006， 博士

【摘要】 飞秒激光具有极高的峰值功率及很短的脉冲持续时间，用它对材料进行微结构修饰是当今材料和信息科学研究的一个新领域。无机-有机杂化材料集无机、有机性质于一体，不仅兼有无机、有机材料两者的性能优势，并能够实现功能互补和协同优化，在光电应用中显示出了巨大的发展潜力。如何利用飞秒激光来诱导和调控无机-有机杂化材料的微结构，以获得光子学新材料，已经成为了材料科学、物理和信息等领域广泛关注和研究的热点课题。本论文对飞秒激光诱导无机-有机杂化光子学微结构与非线性光学材料进行了比较详细的研究。研究的主要内容包括偶氮染料掺杂杂化材料的飞秒激光诱导双折射性能、酞菁染料掺杂无机-有机杂化材料的飞秒激光诱导光Kerr效应、有机染料掺杂材料的飞秒激光诱导体微光栅以及偶氮染料掺杂无机-有机杂化材料的非共振全光极化等研究。实现了偶氮染料掺杂无机-有机杂化材料和聚甲基丙烯酸甲酯（PMMA）聚合物的飞秒激光诱导双折射效应，两种材料的光诱导透过率分别为92％(折射率改变值为5.2×10^-5)和21％(折射率改变值为1.6×10^-4)。通过对光诱导双折射效应信号的测量，考察了光诱导双折射效应的写入过程和衰减过程。研究表明偶氮染料掺杂PMMA聚合物的光诱导双折射效应主要来源于偶氮分子的重新取向，而偶氮染料掺杂无机-有机杂化材料的光诱导双折射效应主要来源于偶氮分子的光致异构。研究了飞秒激光写入参数对偶氮染料掺杂PMMA聚合物的光诱导双折射效应的影响。研究发现偶氮染料掺杂PMMA聚合物在下列三种写入情况下，飞秒激光诱导双折射的上升速率和信号强度的饱和值由写入光的峰值功率控制：激光重复率、脉冲宽度固定，而改变激光功率；激光功率、脉冲宽度固定，而改变激光重复率；激光功率、重复率固定，而改变激光脉冲宽度。但是，当激光脉冲宽度、脉冲能量固定，而改变写入激光重复率，飞秒激光诱导双折射的上升速率和信号强度的饱和值则由写入光的平均功率控制。考察了样品厚度对偶氮染料掺杂无机-有机杂化材料的飞秒激光诱导双折射效应的影响。研究发现增加样品的厚度会加快光诱导双折射的上升速率，减慢光诱导双折射的衰减速率；光诱导双折射信号强度的饱和值T_sat随样品厚度的增加有明显的增加，最终达到饱和值（80％）；长时间稳定信号强度T_perm受样品厚度的影响很小。基于飞秒激光诱导双折射效应，在偶氮染料掺杂无机-有机杂化材料中实现了光学存储，存储的图像可以保持几星期。获得了酞菁铅掺杂无机-有机杂化材料的飞秒激光诱导超快响应的光Kerr效应。超快响应时间约为200fs，超快响应过程控制整个光Kerr效应信号强度的衰减过程。通过光Kerr效应信号强度和泵浦光功率的关系研究，探明光Kerr效应来源于酞菁铅的三阶非线性光学效应；通过光Kerr效应信号强度和泵浦光与偏振光的偏振方向夹角θ之间的关系研究表明，光Kerr效应来源于飞秒激光诱导瞬态光栅引起的自衍射效应。针对微光栅高衍射效率的要求，研究建立了飞秒激光诱导杂化材料体微光栅的新工艺。考察研究了利用飞秒激光双光束干涉的方法制作激光染料P-Orange掺杂无机-有机杂化材料的一维体微光栅，体微光栅的厚度超过450μm，一级Bragg衍射效率约为35％。在一维体微光栅的基础上，采用四束飞秒激光干涉的方法研究制作偶氮染料（DR1和DY9）和酞菁镍（NiPc）掺杂无机-有机杂化材料的四方晶格类型的二维体微光栅。在相同写入激光条件下，DR1掺杂PMMA聚合物的二维体微光栅的条纹宽度比DY9掺杂无机-有机杂化材料的二维体微光栅的条纹宽度小。研究表明，在相同写入条件下，没有观察到未掺染料无机-有机杂化材料的体微光栅，可见飞秒激光诱导体微光栅的形成直接与掺杂染料相关。实现了偶氮染料掺杂无机-有机杂化材料的非共振全光极化。通过对二次谐波的测量，研究了非共振全光极化的写入过程和衰减过程。研究表明偶氮染料掺杂无机-有机杂化材料的非共振全光极化主要来源于偶氮分子的光致异构。测得DR1掺杂杂化材料的二阶非线性光学系数d₃₃约为10^-3pm/V。在基频光与倍频光功率之比固定在750：1的前提下，随基频光功率的增加二次谐波信号强度的衰减被抑制。更多还原

【Abstract】 Femtosecond （fs） lasers with high peak power and ultrashort pulse width have been used to make microscopic modifications to many kinds of materials through multiphoton absorption, which has become a new research field in materials and information science. Hybrid inorganic-organic materials with unique properties offered by the two components play an important role in the development of photonic devices. The microscopic modifications of hybrid inorganic-organic materials have become a hot research topic in the field of materials, physics, and infomations science.This thesis focuses on fs laser induced microstructures and nonlinear optical materials of hybrid inorganic-organic. We studied fs laser induced birefringence, ultrafast optical Kerr effect, microgratings and nonresonant all-optical poling in hybrid inorganic-organic materials and PMMA polymers doped with azodyes, laser dyes, and phthalocyanines.The photoinduced birefringence induced by a fs laser in hybrid inorganic-organic materials and PMMA polymers doped with azodyes was experimentally demonstrated. The probe transmittances for the induced birefringence in these two kinds of materials were estimated to be 92% and 21%, respectively. The characteristic kinetics of growth and decay of the indued birefringence was investigated by measuring the probe transmittance for the photoinduced birefringence. It is evidenced experimentally that the photoinduced birefringence for the azodyes-doped PMMA polymers is mainly due to the reorientation of the azodye molecules, while the photoinduced birefringence for the azodyes-doped hybrid inorganic-organic materials is mainly due to the trans-cis isomerization of the azodye molecules.The research of the effects of writing conditions on the probe transmittance for the photoinduced birefringence in the azodyes-dopedPMMA polymers confirmed that writing conditions had great impact on the growth rate and saturation value of the photoinduced birefringence. Four cases of writing conditions on the growth kinetics of the probe transmittance for the photoinduced birefringence were sdudied. In the following three conditions: （1） fixing the pulse width and repetition rate of the pulses with variation in the writing power, （2） fixing the writing power and repetition rate with variation in the pulse width and （3） fixing the writing power and pulse width with variation in the repetition rate, the peak power is the dominating parameter. When fixing the energy of the pulses or the incident energy, however, the writing power becomes the dominating parameter. The research of the effects of sample thickness on the probe transmittance for the photoinduced birefringence in the azodyes-doped hybrid inorganic-organic materials confirmed that sample thickness had great impact on the growth rate and saturation value of the photoinduced birefringence. The growth rate remarkably becomes fast and the saturation value increases with a longer saturation time with increasing the sample thickness and that the decay of the probe transmittance for the photoinduced birefringence in thicker sample becomes slower. In addition, the probe transmittance for the saturated photoinduced birefringence △n_sat is saturated at 80% after reaching a critical sample thickness, while the effect of the sample thickness on the permanent photoinduced birefringence △n_perm is not as sensitive as that for △n_sat. We propose a novel method for optical srotage based on the photoinduced birefringence in hybrid inorganic-organic materials. The recorded image can be stored for several weeks.Ultrafast optical Kerr effect （～200 fs） in the order of the time-resolution of the experiment dominating over the decay process was demonstrated in lead （II） phthalocyanine （PbPc）-doped hybrid inorganic-organic materials. The research of the influence of pumping power on optical Kerr signal intensity confirms that the optical Kerr effect origins from third-order nonlinear optical properties of the PbPc molecules. By investigating the dependence of optical Kerr signal intensity on the polarization angle between the pumping beam and the probing beam, we have identified the origin of the optical Kerr effect indetail that the ultrafast response process should be attributed to self-diffraction of the pump pulse by the fs laser indued transient gratings.To increase the diffraction efficiency of the microgratings, a new method of fabricating microgratings in hybrid inorganic-organic materials and PMMA polymers doped with azodyes or phthalocyanines was developed. Holographic one-dimentional volume microgratings with high first-order Bragg diffraction efficiency （greater than 35%） were fabricated in the laserdyes-doped hybrid inorganic-organic materials by two-beam interference of fs pulses. The micrograting depth was greater than 450 μm. Based on one-dimensional volume microgratings, holographic two-dimensional volume microgratings were also fabricated in the azodyes- or phthalocyanines-doped materials by four-beam interference of fs pulses. Under the same writing conditions, the linewidth of the strip of the two-dimensional microgratings fabricated in the azodye-doped PMMA polymers is narrower than that of the strip of the two-dimensional microgratings in the azodye-doped hybrid inorganic-organic materials. The photodecomposition of the dyes doped is responsible for the microgratings.Nonresonant all-optical poling in the azodye-doped hybrid inorganic-organic materials was demonstrated. The characteristic kinetics of growth and decay of the photoinduced second-order nonlinear optical effect was measured by second-harmonic generation. It is evidenced experimentally that the nonresonant all-optical poling of the azodyes-doped hybrid inorganic-organic materials is mainly due to the trans-cis isomerization of the azodye molecules. The second-order nonlinear optical coefficient d₃₃ is determined to be 10^-3 pm/V. The decay for the photoindcued second harmonic intensity is improved when increasing the power of the seeding beams, with the intensity ratio between the fundamental and the second harmonic light kept at 750: 1.更多还原