基于反饱和吸收和自聚集两种效应的光限幅器

用酞菁酮金属有机染料首次演示了基于反饱和吸收和自聚焦两种效应的光限幅器。实验和理论分析表明，这种限幅器的输入阈值功率由反饱和吸收决定，而自聚焦使限幅器的最大限幅输出功率降低，限幅效果显著增强。     

有机材料ZnTBP—CA—PhR的非线性吸收和光学限幅性能

报道了一种新型有机材料znTBP—CA—PhR的光学非线性吸收特性，此材料在激光作用下，在可见光区域具有反饱和吸收，再反饱和吸收和饱和吸收效应．同时发现该材料优良的光学限幅性能，不仅光限幅的阈值低，而且限幅前光透射呈线性状态没有光学非线性效应．用5能级结构模型及速率方程模拟了饱和及反饱和的实验曲线，分析了非线性吸收等的物理机理．     

有机材料ZnTBP-CA-PhR的非线性吸收和光学限幅性能

报道了一种新型有机材料ZnTBP-CA-PhR的光学非线性吸收特性，此材料在激光作用下，在可见光区域具有反饱和吸收，再反饱和吸收和饱和吸收效应.同时发现该材料优良的光学限幅性能，不仅光限幅的阈值低，而且限幅前光透射呈线性状态没有光学非线性效应.用5能级结构模型及速率方程模拟了饱和及反饱和的实验曲线，分析了非线性吸收等的物理机理.     

被动光学限幅器的机制与研究进展

被动光学限幅器是利用介质的非线性光学性质实现对光的强度进行控制的器件，它在科研，军事和民用方面都具有广泛的应用，文章讨论了被动光学限幅器的反饱和吸收，双光子吸收，自由载流子吸收，非线性折射，光致散射和光折变机制，每种机制在光限幅器应用中的有效性及局限性，介绍了国内外研究状况及自己的工作；指出了今后被动光学限幅器研究的发展方向。     

被动光学限幅器的机制与研究进展

被动光学限幅器是利用介质的非线性光学性质实现对光的强度进行控制的器件,它在科研、军事和民用方面都具有广泛的应用.文章讨论了被动光学限幅器的反饱和吸收、双光子吸收、自由载流子吸收、非线性折射、光致散射和光折变机制,每种机制在光限幅器应用中的有效性及局限性;介绍了国内外研究状况及自己的工作;指出了今后被动光学限幅器研究的发展方向.     

萘酞菁铅化合物的光限幅特性研究

应用调Q倍频ns/ps Nd：YAG脉冲激光,在波长为532nm,脉冲宽度为8ns,重复频率为1Hz的条件下,研究了溶于二甲基亚砜(DMSO)中的萘酞菁铅溶液的反饱和吸收和光限幅特性。实验表明,萘酞菁铅具有良好的光限幅特性,它的有效激发态吸收截面与基态吸收截面的比值约为15．21,大于萘酞菁铜。研究结果表明,萘酞菁铅的光限幅特性优于C60,激发态吸收是其主要的光限幅机理。实验结果证实了重原子效应可以通过增强系际跃迁而使三重态的反饱和吸收增强,从而提高光限幅的能力。     

非线性光学 非线性光学器件

O437 2005021108 样品位置和光腰半径变化对折射型光限幅器性能的影响 =Effects of the medium location and the beam-waist radius on the operating performances of the refractive optical lim- iting devices[刊,中]／邓罗根(北京理工大学理学院物理 系．北京(100081)),李英兰…//量子电子学报．-2004, 21(4)．-434—439 以衍射理论为基础,通过数值计算,研究了以自聚焦 和自散焦为基础的非线性折射型光限幅器的光限幅特性, 探讨了样品盒的安装位置和人射光束腰斑半径的变化对 折射型光限幅器工作性能的影响。结果表明,折射型光限     

类卟啉镉溶液的光限幅特性

用类卟啉镉的热自散焦和反饱和吸收效应实现了对连续激光的限幅。并提出了一种改进的热自散焦限幅装置。     

基于SBS光限幅和金属酞菁光限幅相结合的复合型光限幅器的研究

为了使受激布里渊散射(SBS)光限幅器的输出能量更"平",提出了一种基于SBS光限幅和金属酞菁光限幅相结合的复合型光限幅器的方案,即SBS光限幅后边放置金属酞菁光限幅,在两种光限幅器的共同限幅作用下,使复合型光限幅器的输出光能量更"平". 数值模拟了该复合型光限幅器的输出光能量随入射光强度的变化曲线,并在Countinuum's Nd: YAG种子注入式激光器中进行了实验验证. 理论和实验结果均表明,复合型光限幅器的输出光能量比单独SBS光限幅器更"平". 关键词： 复合型光限幅器 SBS光限幅 金属酞菁限幅     

C60／PSt复合材料的反饱和吸收与光限幅特性

报道了Ｃ６０／ＰＳｔ（Ｐｏｌｙｓｔｒｅｎｅ）复合材料的制备，测量了材料的线性吸收光谱，研究了不同线性透射率的Ｃ６０／ＰＳｔ材料的反饱和吸收与光限幅特性．     

S1 singlet excited-state absorption of DODCI

1 excited-state absorption cross-section spectrum of DODCI in ethylene glycol is determined in the wavelength range from 500 nm to 750 nm. The S₁ state is populated by amplified femtosecond dye laser pulses (wavelength 592 nm) and the S₁-state absorption and emission behaviour is probed with a femtosecond light continuum. A general analysis procedure is developed to extract absolute excited-state absorption cross-sections from the measured transmissions. For DODCI in ethylene glycol the wavelength regions of saturable absorption (mode-locking application), reverse saturable absorption (optical limiter application), and effective stimulated emission (laser application) are determined. Received: 25 July 1996     

High-efficiency multipass optical limiter

We report experimental results on a highly efficient optical limiter that uses a three-mirror, multipass ring configuration. The optical limiter's enhanced performance is based on the accumulative effect that is achieved when the laser beam passes through the sample several consecutive times. Its feasibility was demonstrated for media with different limiting action processes, namely, reverse saturable absorption, nonlinear scattering, and thermal lensing. We employed a frequency-doubled, Q-switched, 10-ns Nd:YAG laser operating at a 5-Hz repetition rate.     

Wavelength dependence of nonlinear absorption in a bis-phthalocyanine studied using the Z-scan technique

The wavelength dependence of the nonlinear absorption of a bis-phthalocyanine, Nd(Pc)₂, dissolved in dimethyl formamide was studied in the rising part of the Q-band using the open aperture Z-scan technique, to determine the wavelength region over which the nonlinear absorption changes from reverse saturable absorption to saturable absorption. It was found that the sample could be used as a reverse saturable absorber, and hence as an optical limiter, up to a wavelength of about 604 nm. The imaginary part of the third order susceptibility was also calculated for these wavelengths. Resonant enhancement of the imaginary part of the third order susceptibility was clearly observed. Received: 26 April 2002 / Revised version: 30 June 2002 / Published online: 20 December 2002 RID="*" ID="*"Corresponding author. Fax: +91-484/576-714, E-mail: kpu@cusat.ac.in RID="**" ID="**"Present address: Optical Sciences Center, University of Arizona, Tucson, USA     

An analysis of pulse propagation through a saturable absorber having excited-state absorption

The theoretical study of the propagation of a bell-shaped light pulse through a saturable absorber having excited-state absorption is presented. Assuming that the pulse-width is longer than the first excited-state lifetime of the absorber, a general expression for the steady-state transmission of the absorber is obtained. It is shown that when the excited-state absorption cross-section is larger than the ground-state absorption cross-section (reverse saturable absorber) the absorber acts as a power limiter. An explicit expression for the change of temporal pulse-width in a single transit through the absorber is obtained, which shows that the pulse-width increases due to the presence of excited-state absorption. An analytical expression is presented for the optimum pulse intensity at which the maximum pulse broadening occurs.     

All-fiber erbium-doped dissipative soliton laser with multimode interference based on saturable-reserve saturable hybrid optical switch

Reverse saturable absorption is essential for the realization of dissipative solitons. In this paper, we introduce reverse saturable absorption by using nonlinear multimode interference (NL-MMI), for the first time, to the best of our knowledge, and obtain a stable dissipative soliton operation. By adjusting the coupling efficiency from multimode fiber to single mode fiber, the absorption properties of NL-MMI can be switched between saturation and reverse saturation. The dissipative soliton can be obtained with pulse width of 975 fs in the experiment, the 3-dB bandwidth at 1555 nm is 16 nm, and the maximum output power is 11.48 mW. The nonlinear absorption optical modulation and high damage threshold characteristics of the NL-MMI based ultrafast optical switch provide a new idea for realizing dissipative solitons.     

Optical limiting and pulse reshaping of picosecond pulse trains by fullerene C60

We present a dynamical theory of nonlinear absorption and propagation of a laser pulse train that contains 20 subpulses with an individual pulse width of 100 ps. It is shown that the accumulative nonlinearity and the reverse saturation absorption play important roles in the optical limiting performance and pulse shaping. When the incident field is not too strong, the population transfer reveals a slow response process, and the periodic sequence of short light pulses can be regarded as a continuous long pulse. The general theory is applied to fullerence C₆₀, which is a popular reverse saturable absorption material and a good limiter because of its larger excited-state absorption cross-section compared with that of the ground state. The propagation of the front subpulses is mainly affected by the linear transition between the ground state and the first excited singlet state, while the latter subpulses are attenuated by the excited-state absorption. Moreover, these two different kinds of absorption mechanisms result in different radial distributions for different subpulses. The pulse propagation is studied by solving numerically the coupled rate equations and the propagation equation of the optical pulse intensity, using experimental parameters as input. We suggest a new method to measure the lifetime of the triplet state.     

掺Er3+玻璃的光限幅特性研究

利用波长为532 nm的皮秒脉冲激光,研究了掺Er3 玻璃的光限幅特性和反饱和吸收.当入射功率不断增加且超过一定阈值时,透射功率不再随着入射功率快速增大,而是逐渐趋向于较稳定状态,从而实现了对强激光的光限幅效应.进一步利用布居速率方程讨论了其机制并给出了激发态的吸收截面,结果表明激发态吸收是其主要的光限幅机理.     

Flexible alteration of optical nonlinearities of iodine charge-transfer complexes in solutions

The type of donor used is found to influence greatly the optical nonlinearities of iodine charge-transfer (CT) complexes in solutions for several solvents. The magnitude and sign changes of nonlinear absorption of iodine CT complexes for different solvents as donors are observed, which implies the transition from saturable absorption to reverse saturable absorption. Compared with C60 in toluene, iodine CT complexes with toluene and benzene demonstrate larger reverse saturable absorption. Meanwhile, flexible alteration of optical nonlinearities is easily obtained by adjusting the mixture ratio of different solvents, yielding a prospective means of constructing a nonlinear medium with a large nonlinear coefficient.