Investigation of the optical limiting properties of acid blue29 in various solvents

The optical limiting properties of acid blue29 solutions in different solvents are investigated. Experiments are performed using a CW He-Ne Laser beam at 632.8 nm wavelength and 35 mW power. The strength of the optical limiting action is dramatically influenced by the solvent. Multiple diffraction rings were observed when the samples were exposed to laser radiation. The effect of concentration, solvent and laser intensity on the diffraction rings are studied experimentally. Our results show that the nonlinear refraction is the dominant mechanism to explain the optical limiting behavior in acid blue29.     

Broadly tunable mid-infrared femtosecond optical parametric oscillator using all-solid-state-pumped periodically poled lithium niobate

We describe a high-repetition-rate femtosecond optical parametric oscillator (OPO) that was broadly tunable in the mid infrared. The all-solid-state-pumped OPO was based on quasi-phase matching in periodically poled lithium niobate. The idler was tunable from approximately 1.7 mum to beyond 5.4 mum, with maximum average power levels greater than 200 mW and more than 20 mW of average power at 5.4 mum. We used interferometric autocorrelation to characterize the mid-infrared idler pulses, which typically had durations of 125 fs. This OPO had a pumping threshold as low as 65 mW of average pump power, a maximum conversion efficiency of >35% into the near-infrared signal, a slope efficiency for the signal of approximately 60%, and a maximum pump depletion of more than 85%.     

Photorefractive properties of potassium lithium niobate doped with copper

Potassium lithium niobate doped with copper (Cu:KLN) were grown by the Czochralski method for the first time. The structure of Cu:KLN was measured by the x-ray powder diffraction method, and its lattice constants were obtained. The position of copper ions in KLN crystal was determined. The exponential gain coefficient, response time and erasure time were measured. It was found that the exponential gain coefficient of Cu:KLN is 10.5 cm⁻¹, as two times high as that of KLN, and its response time of 1.53 s is one order of magnitude shorter than that of Cu:LiNbO₃. The type of light exciting carriers in Cu:KLN has been investigated. The result showed that the electron acts the main role in Cu:KLN.     

重频激光对多壁碳纳米管悬浮液光限幅特性的影响研究

在激光以不同重复频率入射下,研究了直径分布为10～20 nm的多壁碳纳米管悬浮液对波长为1064 nm激光的光限幅效应,定性分析了不同重复频率激光对多壁碳纳米管悬浮液的光限幅影响。结果表明:碳纳米管悬浮液对波长为532 nm和1064 nm的激光都具有很强的光限幅响应;在多脉冲激光入射时,碳纳米管悬浮液的光限幅效应比单脉冲激光入射时更显著。     

Synchronously pumped femtosecond optical parametric oscillator of congruent and stoichiometric MgO-doped periodically poled lithium niobate

A synchronously pumped femtosecond optical parametric oscillator based on congruent MgO-doped periodically poled lithium niobate (c-MgO:PPLN) is reported. The system, operating at room temperature, was pumped by a mode-locked Ti:sapphire laser. The wavelengths of the signal and idler waves were tuned from 870 nm to 1.54 μm and 1.58 to 5.67 μm, respectively, by changing the pump wavelength, the grating period or the cavity length. Pumped by 1.1 W of 755 nm laser radiation, the OPO generated 310 mW of 1080 nm radiation. This signal output corresponds to a total conversion efficiency of 50%. Without dispersion compensation the OPO generated phase-modulated signal pulses of 200 fs duration. Besides the OPO of c-MgO:PPLN, an OPO of stoichiometric (s) MgO:PPLN was investigated. Because of the reduced sensitivity to photorefractive damage, both crystals allowed efficient OPO operation at room temperature. Received: 19 August 2002 / Revised version: 11 December 2002 / Published online: 19 March 2003 RID="*" ID="*"Corresponding author. Fax: +49-631/205-3906, E-mail: andres@physik.uni-kl.de     

Nonlinear optical and optical limiting properties of individual single-walled carbon nanotubes

A large number of individual single-walled carbon nanotubes (SWNTs) were obtained by dilution of nanotube dispersions in N-methyl-2-pyrrolidone (NMP). Up to 70% individual SWNTs are contained in the NMP dispersions with concentrations of less than 4.0×10^-3 mg/mL. The nonlinear optical and optical limiting properties of SWNT dispersions were studied by using the Z-scan technique at 532 nm. As the concentration of SWNTs is increased, the nonlinear extinction (NLE) and optical limiting effects improve significantly, while the limiting thresholds decrease gradually. The individual SWNTs show similar NLE effect to zinc phthalocyanine nanoparticles, while also exhibiting larger NLE coefficients than Mo₆S_4.5I_4.5 nanowires.     

Influence of structure on the optical limiting properties of nanotubes

We investigate the role of carbon nanotubes structure on their optical limiting properties. Samples of different and well-characterized structural features are studied by optical limiting and pump-probe experiments. The influence of the diameter's size on the nano-object is demonstrated. Indeed, both nucleation and growth of gas bubbles are expected to be sensitive to diameter.     

Influence of optical-damage-resistant dopants on the nonlinear optical properties of lithium niobate

Using the chemical-bond method, nonlinear optical properties of lithium niobate containing different dopants are calculated. In crystals with stoichiometric composition the second order nonlinear susceptibility decreases approximately linearly with increasing dopant concentration. Among the dopants studied – Mg, Zn and In – this behaviour is most highly expressed for In doping. In contrast to that, congruently grown crystals show a different behaviour; only a weak dependence on the dopant concentration is found for, for example, Mg-doped material. Received: 24 October 2000 / Published online: 21 March 2001     

Enhanced optical limiting properties in suspensions of CdO nanowires

Optical limiting (OL) properties of CdO nanowires in water and ethanol were investigated by using nanosecond laser pulses at 532 nm. Experimental results show that suspension of CdO nanowires in ethanol exhibits better OL property than solution of C₆₀ in toluene and suspension of CdO nanowires in water. The dominant mechanism for the observed enhanced optical limiting in ethanol suspensions of CdO nanowires is due to nonlinear scattering.     

Z-scan and optical limiting properties of Hibiscus Sabdariffa dye

The intensity-dependent refractive index n ₂ and the nonlinear susceptibility χ ⁽³⁾ of Hibiscus Sabdariffa dye solutions in the nanosecond regime at 532 nm are reported. More presicely, the variation of n ₂, β, and real and imaginary parts of χ ⁽³⁾ versus the natural dye extract concentration has been carried out by z-scan and optical limiting techniques. The third-order nonlinearity of the Hibiscus Sabdariffa dye solutions was found to be dominated by nonlinear refraction, which leads to strong optical limiting of laser.     

新型金属团簇化合物的光限幅特性研究

应用倍频 Nd:YAG脉冲激光 ,在波长为 5 32 nm、脉冲宽度为 8ns的条件下 ,研究了金属团簇化合物WOS3Cu3I(2 - Me Py) 3的光限幅特性。其光限福特性优于富勒烯。Z- Scan研究结果表明 :该团簇具有自聚焦特性 ,其光限幅起源于激发态吸收     

Growth and optical properties of Hf,Ce co-doped lithium niobate crystals

In this paper, a series of Hf,Ce co-doped lithium niobate crystals with various HfO₂ concentrations were grown by Czochralski method. The ultraviolet-visible absorption spectra and the infrared transmittance spectra were measured to study defect structure of the crystals. The optical damage resistance was measured by the transmitted facula distortion method. The results showed that the optical damage resistance of Hf:Ce:LiNbO₃ was greatly improved when the Hf-doping concentration was above 4 mol%.     

飞秒激光诱导自组织纳米周期结构及其光学特性的研究进展

飞秒激光具有超快、超强的特点.飞秒激光微纳加工发展非常迅速. 本文综述了近十年来利用飞秒激光在金属、半导体、介质等各类材料中制备的纳米周期结构, 阐述了若干关于飞秒激光诱导纳米周期结构的物理机理的观点.讨论了基于偏振调制的多光束 干涉在半导体表面制备纳米周期结构,简要叙述了周期结构对材料光学特性的影响. 关键词： 飞秒激光 纳米周期结构 多光束干涉 光学特性