基于激发态非线性折射效应的全光开关与光限幅

提出一种新型的光控光开关,以532nm脉冲激光入射金属-类卟啉有机材料,强激发态吸收导致瞬态透镜效应,使同时通过介质的632.8nm激光实现光开关,实验演示了开关特性,开启和关闭时间均为100ns.还演示了激发态吸收和非线性折射两种效应共同作用的单光束光限幅.对上述两种基于非线性折射效应的器件特性进行了理论分析.     

基于激发态非线性拆射效应的全光开关与光限幅

提出一种新型的光控光开关，以５３２ｎｍ脉冲激光入射金属－类卟啉有机材料，强激发态吸收导致瞬态透镜效应，使同时通过介质的６３２．８ｎｍ激光实现光开关，实验演示了开关特性，开启和关闭时间均为１００ｎｓ，还演示了激发态吸收和非线性折射两种效应共同作用的单光束光限幅，对上述两种基于非线性折射效应的器件特性进行了理论分析。     

相位物体Z-扫描研究金属簇合物[Tp*W(μ3-S)3Cu3Py3(μ3-Br)](PF6)/DMF溶液的瞬态热致非线性折射

在纳秒时域,采用相位物体(PO)Z-扫描技术研究了一种新型金属簇合物溶液的瞬态热致非线性效应.该方法的最大优点是很容易区分瞬态热致非线性折射和三阶非线性折射.本文利用PO Z-扫描和传统Z-扫描研究了在8 ns脉宽、不同能量激光脉冲作用下[Tp*W(μ3-S)3Cu3Py3(μ3-Br)](PF6)/DMF溶液的光学非线性.从声波方程和热传导方程出发,对实验结果进行了理论分析和数值模拟,理论值和实验结果很好的吻合.研究结果表明,样品溶液的非线性折射主要来源于瞬态热致非线性效应.     

高斯光束通过非线性折射和吸收介质的光强分布

以衍射理论为基础,推导并模拟了高斯光束通过非线性折射和吸收效应介质后的远场光强分布。结果表明:入射高斯光束引起的介质折射率变化和光束波前曲率影响介质出射面光束的径向调制相位,安装在焦点前的有自聚焦效应的介质和安装在焦点后的有自散焦效应的介质具有闪耀光栅的能力,使远场出现中心为暗斑外侧为亮环的衍射图样。非线性折射效应为主的介质,其非线性吸收效应的变化同时改变远场衍射图样的数目和光强值,但对于非线性吸收效应为主的介质,衍射图样的数目随吸收效应的变化不明显,吸收效应只影响光强值。     

相位物体$lt;i$gt;Z$lt;/i$gt;-扫描研究金属簇合物［$lt;i$gt;Tp$lt;/i$gt;*W($lt;i$gt;μ$lt;/i$gt;$lt;sub$gt;3$lt;/sub$gt;-S)$lt;sub$gt;3$lt;/sub$gt;Cu$lt;sub$gt;3$lt;/sub$gt;$lt;i$gt;Py$lt;/i$gt;$lt;sub$gt;3$lt;/sub$gt;($lt;i$gt;μ$lt;/i$gt;$lt;sub$gt;3$lt;/sub$gt;-Br)］($lt;i$gt;PF$lt;/i$gt;$lt;sub$gt;6$lt;/sub$gt;)/DMF溶液的瞬态热致非线性折射

在纳秒时域,采用相位物体（PO）Z-扫描技术研究了一种新型金属簇合物溶液的瞬态热致非线性效应.该方法的最大优点是很容易区分瞬态热致非线性折射和三阶非线性折射.本文利用PO Z-扫描和传统Z-扫描研究了在8 ns脉宽、不同能量激光脉冲作用下［Tp*W（μ₃-S）₃Cu₃Py₃（μ₃-Br）］（PF₆）/DMF溶液的光学非线性.从声波方程和热传导方程出发,对实验结果进行了理论分析和数值模拟,理论值和实验结果很好的吻合.研究结果表明,样品溶液的非线性折射主要来源于瞬态热致非线性效应. 关键词： Z-扫描')" href="#">相位物体 Z-扫描 瞬态热致非线性折射 光克尔效应 DMF     

富勒烯衍生物中的自散焦、自聚焦及其相互转化

用Z扫描方法研究了富勒烯有机铬衍生物fac- and mer- [bis (1,2-diphenylphosphino) ethane] (tricarbonyl) (η²-fullerene-C₆₀) chromium的非线性折射特性;用速率方程理论分析了激发态光学非线性材料非线性折射行为,以及大光强下高阶激发态折射度如何引起材料自散焦-自聚焦相互转化.计算出了转变光强.并数值模拟了不同光强下Z扫描实验曲线的变化过程.理论计算与实验符合得较好. 关键词： 自散焦 自聚焦 富勒烯衍生物 Z扫描     

三维手性壳状银纳米结构的非线性饱和吸收特性研究（英文）

采用微球自组装及倾斜真空热蒸镀技术制作了三维手性壳状银纳米结构,采用Z扫描技术研究了该样品在532nm波长、4ns脉宽的Nd:YAG激光入射下的非线性饱和吸收特性。研究结果表明,当入射激光强度达到2.5×10~9 W/cm~2时,其非线性吸收系数可达-1.45×10~(-5) cm/W,该结果比文献报道的悬浮液中的胶体银纳米颗粒的非线性吸收系数(-1.5×10~(-9) cm/W)大四个数量级。实验还发现,该样品的非线性吸收系数随着入射激光的偏振方向改变而出现明显的变化。文中对其非线性吸收的增强机理及偏振依赖性进行了分析讨论。     

超短激光脉冲在水中的非线性传输特性研究

基于扩展的非线性薛定谔方程及与其耦合的电子密度演化方程,理论研究了超短激光强脉冲在水中的非线性传输特性.理论模型综合考虑了衍射、正常群速度色散,多光子吸收、自聚焦及激光诱导产生的等离子体对光脉冲的自散焦效应.采用有限差分法模拟得到超短脉冲在传输过程中轴向上光功密度和等离子体密度的时空分布.系统分析了超短脉冲在水中传输的动力学过程,讨论了非线性自聚焦和等离子体自散焦效应在脉冲传输过程中的竞争关系.同时研究了不同入射激光能量,脉宽和聚焦条件对等离子体丝的时宅结构和脉冲能流横向分布的影响.该研究将有助于理解和推动超短光脉冲在激光医学、激光安全防护和水中激光加工中的应用.     

激光聚焦位置对K9光学玻璃损伤的影响

 利用脉宽为10 ns、波长为1 064 nm的激光脉冲聚焦通过K9玻璃的方法,研究了玻璃的损伤形貌与高强度纳秒激光脉冲聚焦位置的关系。当激光脉冲聚焦在样品中心时,吸收能量随着入射能量的增加呈线性增长,玻璃的破坏范围不断扩大;当激光脉冲聚焦在样品表面时,吸收能量随着入射能量的增加呈先增长而后减小最终趋于平稳,玻璃表面的破坏范围也是先增大而后减小趋于平稳,这主要是由于空气被击穿而吸收大量能量引起的。     

有机材料反饱和吸收特性分析

从能级角度出发,结合入射激光脉宽对粒子吸收方面的影响,用速率方程模拟了各能级粒子数的瞬时变化关系,给出了激光脉宽与能级寿命可比拟时反饱和吸收的动态解,表明粒子在能级上的分布情况。用C60和HITCI(1,1′,3,3,3′,3′hexa methyl lindo tricarbocyanine Iodide)的实验参数理论模拟了激发态吸收截面大于基态吸收截面时透射率随光强的变化关系,用以说明大的上能级吸收截面可以抑制光强过大时引起的饱和吸收,增强材料的非线性光限幅特性。     

Concentration dependent nonlinear refraction in chloroaluminum phthalocyanine/ethanol solution

Nonlinear refractive properties of chloroaluminum phthalocyanine (CAP) in ethanol solution are studied using the Z-scan technique with picosecond (ps) and nanosecond (ns) laser pulses at a wavelength of 532 nm. A transition from self-focusing to self-defocusing in CAP solution excited by 10 ns pulses is observed during the decrease of its concentration. This transition is due to co-existing excited-state refraction and transient thermal lensing effects. The experimental results are described very well using the rate-equation model and the theory of transient thermal refraction in liquids. The refractive cross sections of the excited-state are also obtained.     

Dye-laser pulse shortening by transient absorption following excited-state intramolecular proton transfer

Molecules undergoing excited-state intramolecular proton transfer often show transient absorption after pulsed optical excitation, due to the tautomeric form in the singlet ground state. This absorption may be used to suppress, after a short time, the laser action of dyes emitting in the transient absorption band. The method is designed for high photochemical stability. Lasing from PBBO, pumped 10 times above threshold by an excimer pumped PTP dye laser, was suppressed after 3.3ns by the addition of 2-(2-hydroxyphenyl)-benzoxazole, which absorbed 30% of the pump energy. At higher concentrations, intense and stable 80ps PBBO laser pulses were obtained. The pulse evolution is simulated by model calculations. A hypothetical super-dye, consisting of chemically linked laser- and absorber-moities, is also discussed. Here Förster energy transfer should result in particularly efficient laser pulse shortening.     

Saturated absorption and nonlinear refraction of silicate glasses doped with silver nanoparticles at 532 nm

The nonlinear optical characteristics of silicate glasses doped with silver nanoparticles are investigated by Z-scan technique using second harmonic radiation of picosecond Nd:YAG laser (=532 nm, =55 ps). The real and imaginary parts of third-order nonlinear susceptibility of silver-contained glasses were measured. It was found that the sign of Im ⁽³⁾was negative due to saturated absorption and the sign of Re ⁽³⁾ was changed from negative (self-defocusing) to positive (self-focusing) with growth of laser radiation intensity. The mechanisms responsible for saturated absorption and nonlinear refraction are discussed.     

几种新型金属配合物热致三阶非线性光学特性

利用连续激光Z-扫描方法研究了过渡金属Ni、Cu、Pd的新型有机配合物的热致三阶非线性光学特性。结果表明：在488nm和632．8nm波长连续激光激发下,这几种配合物的光学非线性折射主要来源于热效应。并由实验曲线计算了它们的热光系数dn／dT及热致非线性折射率n2。通过比较,发现热致非线性折射率与配合物分子结构、激发波长及在该波长下的线性吸收强弱有关。金属中心原子的原子序数越大,热光系数和折射率也相应的越大。在488nm波长激光激发下的dn／dT和n2大于该配合物在632．8nm波长激发下的dn／dT和n2,在同一波长下,化合物溶液在该波长下的吸收越强,其dn／dT和n2值也越大。     

Nonlinear optical characteristics of a pseudoisocyanine solution

The saturated nonlinear absorption and Kerr nonlinearities of an aqueous pseudoisocyanine solution are investigated at the wavelengths of 532 and 529 nm with the use of pulsed laser radiation of different duration (8 ns and 475 fs). The measured values of the nonlinear refractive indices amount to ?6×10^?12 (t=8 ns) and ?8×10^?14 cm²W^?1 (t=475 fs). The change in self-action effects in pseudoisocyanine from self-defocusing to self-focusing revealed in the case of increasing intensity of femtosecond laser pulses is attributed to the effect of a fifth-order nonlinear optical process. The nonlinear refractive index responsible for this process amounts to 4×10^?24 cm⁴ W^?2. The imaginary part of the third-order nonlinear susceptibility, responsible for the induced transparency of the pseudoisocyanine solution, is Imχ ⁽³⁾=?2×10^?12 esu. Temporal changes in the shape of nanosecond laser pulses due to the nonlinear refraction induced by a thermal process are analyzed.     

Transformation of Sign of Nonlinear Refraction between Mo（W）/S/Cu Planar Metal Clusters

Optical nonlinear refractive properties of a series of Mo（W）/S/Cu planar square clusters are investigated using the Z-scan technique with the ns laser pulses at the wavelength of 532 nm. The result shows that the planar metal clusters containing the halogen ligands demonstrate the self-focusing effect, and the other planar metal dusters demonstrate the self-defocusing effect. These facts indicate that the halogen ligands can act as crucial factors in determining the sign of the nonlinear refraction of the Mo（W）/S/Cu planar metal clusters. The analysis of the experimental data shows that the planar clusters with halogen ligands possess greater refraction volume of the excited state than that of the ground state, while the other planar clusters possess the smaller refraction volume of the excited state than that of the ground state.     

The nonlinear refraction and absorption dependence on the thermal effect for 4 ns pulse duration in binuclear Zn(II) phthalocyanine solution

The influence of thermal effect on the third-order nonlinear optical properties of binuclear Zn(II) phthalocyanine in chloroform solution was studied. The nonlinear refraction and absorption of the sample was measured by using Z-scan technique with 4 ns laser pulses at 532 nm wavelength. The opposite signs of the effective nonlinear refraction index were observed by changing the focal length of focusing lens from 10 cm to 20 cm in the experimental setup. Changing the focusing lens increased the beam waist radius from 7 μm to 20 μm. The nonlinear absorption coefficient was reduced about 200 times based on changing the fluence or beam waist radius. The drastic changes in the third-order nonlinear optical parameters were attributed to thermal effect. To investigate the role of thermal effects even further the effective nonlinear refraction and absorption coefficients were studied by using different repetition rates, input powers and concentrations.     

nc-Ge/SiN_x多层膜材料的可调控非线性光学特性

采用等离子体增强化学气相沉积和后退火的方法制备了纳米锗/氮化硅(nc-Ge/SiN_x)多层薄膜。借助Raman光谱仪对其微结构进行表征,测得样品的晶化率大于46%。由样品的光吸收谱可知,nc-Ge的尺寸越小,其光学带隙越大。利用Z扫描技术对样品的非线性光学特性进行研究,以波长为1 064 nm、脉宽为25 ps的锁模激光作为激发光,测得样品的非线性折射率系数在10~(-10)cm~2/W数量级。实验结果表明,通过改变nc-Ge的尺寸可以使材料的非线性光学折射率由自散焦转变为自聚焦特性,而负的非线性折射率系数可归因于两步吸收产生的自由载流子散射效应。当激发光强增大时,在锗层厚度为6 nm的多层膜中同时存在两步吸收过程和饱和吸收过程。两种非线性光学吸收过程之间的竞争是样品呈现不同非线性光学特性的主要原因。