Broadband optical limiting in the suspensions of lead sulfide nanoparticles

Nanoparticles of lead sulfide (PbS) have been prepared by a surfactant micelle template-inducing reaction. These nanoparticles were dispersed in ethanol and investigated for their nonlinear optical properties by nanosecond laser pulses. Broadband optical limiting effects have been observed at the wavelengths of 355, 1064, and 430 nm and every 30 nm from 470 to 620 nm. The nonlinear light-scattering process in the suspensions of PbS nanoparticles was characterized at the wavelength of 532 nm. Nonlinear absorption and nonlinear scattering were deduced to be the mechanisms for the broadband optical limiting performance. The origins of the nonlinear scattering were discussed.     

基于光声光谱联合主成分回归法的血糖浓度无损检测研究

利用可调谐脉冲激光器激发联合聚焦超声探测器前向探测模式搭建了一套血糖光声无损检测实验装置。为了测试该装置的可靠性,实验中利用532 nm泵浦Nd∶YAG调Q脉冲激光器激发不同浓度的葡萄糖水溶液产生实时光声信号;采用脉冲激光在近红外波段1 300～2 300 nm内固定间隔波长10 nm扫描方式激发不同浓度的葡萄糖水溶液,获取了不同波长下的葡萄糖光声峰峰值,利用差谱方法筛选出了多个葡萄糖的特性波长;然后采用主成分回归算法优选了三个特性波长,并建立了浓度梯度与对应三个优选波长光声峰峰值之间的数学校正模型。实验表明,葡萄糖水溶液的光声信号符合弱吸收介质的柱状光声源模型;利用建立的校正模型对校正集和预测集的葡萄糖浓度预测结果表明,葡萄糖浓度的校正和预测均方根误差均小于10 mg·dl-1,相似系数为0.993 6。     

基于OPO脉冲激发的血糖光声检测影响因素研究

构建了一套基于侧向模式的光学参数振荡(optical parameter oscillator,OPO)脉冲激光激发-超声传感的血糖光声检测系统,并且将激发波长、激光能量、探测频率和温度等对血糖光声检测的影响,在系统结构上进行了有效融合。然后,以不同浓度的葡萄糖溶液作为测试样品,实验研究了几个因素(激发波长、激光能量、探测频率和温度等)对葡萄糖光声检测和浓度预测的影响。实验得到了不同浓度葡萄糖溶液在不同影响因素条件下的葡萄糖实时光声信号和光声峰峰值,同时,为了得到不同因素对葡萄糖光声值和浓度预测的影响规律,通过线性回归算法建立了葡萄糖光声峰峰值与各因素变化,以及不同因素下光声峰峰值与浓度梯度的映射关系模型。实验和模型预测结果表明：相比1 200和1 300 nm波长而言,1 064 nm波长下的葡萄糖光声峰峰值与浓度梯度模型预测效果最好,模型相关系数达到0.986;葡萄糖光声峰峰值随着脉冲激光输出能量的增大呈线性增大趋势,且葡萄糖浓度预测准确度随着激光输出能量增大有所提高;根据不同探测频率的超声探测器捕获的葡萄糖光声峰峰值与浓度梯度建模效果来看,响应频率为1 MHz的超声探测器相比2.5和10 MHz的超声探测器,在葡萄糖光声信号探测上具有更好的探测效果;最后,实验发现,葡萄糖光声峰峰值随着温度和浓度的增大均呈线性增大趋势,且浓度预测误差随着温度的升高逐渐增大。     

Generation of flat-top waveform in the time domain based on stimulated Brillouin scattering

A method of generating a flat-top waveform in the time domain based on stimulated Brillouin scattering (SBS) is proposed. The transmitted pulses are simulated with pump wavelength at 1064 nm and 532 nm, respectively, and validated in the experiment performed with the Nd:YAG seed-injected laser. The experimental results agree well with the theoretical simulation. With 532 nm pump wavelength, the top of the transmitted pulse is almost a platform, while there is a peak in the front and a platform in the back with 1064 nm pump wavelength. The mechanism behind the generation of flat-top waveform with 532 nm pump wavelength is analyzed in details. PACS 42.65-k; 42.65.Es; 42.65.Hw     

Nonlinear optical parameters and optical limitation in cobalt-doped polyvinylpyrrolidone solutions

Nonlinear optical parameters (nonlinear refractive indices and nonlinear absorption coefficients) of solutions of polyvinylpyrrolidone doped by cobalt to various concentrations are measured at the lasing and second-harmonic wavelengths of a picosecond Nd:YAG laser (λ=1064 and 532 nm, respectively, and τ=35 ps). Data on optical limitation in these solutions are presented. The absence of nonlinear absorption in the IR spectral range and its significant effect in the visible range are demonstrated. Optical limitation at a wavelength of 1064 nm is related to defocusing, whereas at 532 nm, this effect is caused by two-photon absorption and partially by inverse saturated absorption and defocusing. Nonlinear optical parameters of metal-polymer complexes are reported.     

三硼酸锂晶体上1064 nm,532 nm,355 nm三倍频增透膜的设计

采用矢量法设计了三硼酸锂晶体上1064 nm、532 nm和355 nm三倍频增透膜,结果表明1064 nm、532 nm和355 nm波长的剩余反射率分别为0.0017%、0.0002%和0.0013%。根据误差分析,薄膜制备时沉积速率精度控制在 5.5%时,1064 nm、532 nm和355 nm波长的剩余反射率分别增加至0.20%、0.84%和1.89%。当材料折射率的变化控制在 3%时,1064 nm处的剩余反射率增大为0.20%,532 nm和355 nm处分别达0.88%和0.24%。与薄膜物理厚度相比,膜层折射率对剩余反射率的影响大。对膜系敏感层的分析表明,在1064 nm和355 nm波长,从入射介质向基底过渡的第二层膜的厚度变化对剩余反射率的影响最大,其次是第一膜层。在532 nm波长,第一和第三膜层是该膜系的敏感层。同时发现,由于薄膜材料的色散,1064 nm5、32 nm和355 nm波长的剩余反射率分别增加至0.15%、0.31%和1.52%。     

A compact and high efficiency diode pumped green laser based on MgO doped PPLN

In this work, an efficient intra-cavity second harmonic generation of green laser in a periodically poled MgO doped LiNbO₃ (MgO:PPLN) bulk crystal using a compact Nd:YVO₄ laser as a fundamental laser source is reported. Different length, different working temperature MgO:PPLN crystals are tested and investigated in the SHG experiments. The maximum output power at 532 nm is 6.2 W at the absorbed pump power at 808 nm of 14 W, the optical to optical conversion efficiencies from 808 to 532 nm and 1064 to 532 nm are 43 and 77%, respectively, the instability in 2 hours is less than 5%.     

Determination of the ratio of soot refractive index function E(m) at the two wavelengths 532 and 1064 nm by laser induced incandescence

A new method is proposed to measure the ratio of the refractive index function of soot particles E(m) at the two fixed wavelengths: 532 and 1064 nm. Using a non-intrusive, in-situ laser based technique, the ratio E(m,1064 nm)/E(m,532 nm) can be determined by comparing laser induced incandescence (LII) intensities at 532 and 1064 nm excitation wavelengths. The method consists of selecting laser energies that insure the equality of the LII signals in the low fluence regime under given conditions. Such equality is consistent with the fact that the soot particle will have reached the same temperature independently of the laser wavelength, i.e. the soot particle has absorbed the same energy. As the absorbed energy is proportional to the laser irradiance times E(m), the measurement of the laser energies required to insure perfect concordance of the LII intensities (spatially and temporally) serves to deduce the ratio E(m,1064 nm)/E(m,532 nm). The method is demonstrated in an acetylene/air flame, validated against extinction measurements performed by cavity ring-down spectroscopy (CRDS) by using laser radiations at 532 nm and 1064 nm and finally applied to different flame conditions. PACS 78.20.Ci; 78.90.+t; 81.05.Uw; 42.62.-b     

激光敌我识别系统中滤光膜的研制

根据激光敌我识别系统的使用要求,选择H4和SiO2作为高低折射率材料,借助Macleod和TFCalc软件进行膜系优化设计和分析。采用电子束真空镀膜的方法并加以离子辅助沉积技术,通过正交矩阵实验对材料的工艺参数进行调整和优化,利用基片的正反面分别对带通滤光片的长波反射带和短波反射带进行展宽,解决了单面膜层过厚难以控制的问题,制备了符合要求的激光滤光膜。镀膜后的基片在532,632,905,1064和1550nm波长处的透射率小于0.2%,808nm波长附近的平均透射率大于95%。并在532nm和1064nm波长处具有较高的激光损伤阈值,能承受恶劣的环境测试,满足激光敌我识别系统中光学仪器的使用要求。     

Experimental Study on Optical Limiting and Transient All-optical Switching Properties of a Cubanelike Transition-metal Cluster Compound (n-Bu4N)3[MoAg3BrI3S4]

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Nonlinear optical properties of a series of azobenzene liquid-crystalline materials

The nonlinear optical properties of a series of azobenzene liquid-crystalline materials, which have different side-chain lengths in their molecular structure from one to another, were investigated using Z-scan method under picosecond pulse laser at 532 nm, 1064 nm and CW 488 nm excitation. The mechanism accounting for the process of nonlinear refraction was discussed under different laser excitations. The polymer films possess very large nonlinear refraction at all the three different laser excitations. Especially, the nonlinear refractive index becomes larger as the length of side-chain, where azobenzene group is contained, increases under pulse excitation at 1064 nm.     

Nonlinear optical characteristics of colloidal solutions of metals

Results of the study of nonlinear optical parameters of colloidal solutions of silver, gold, platinum, and copper by the Z-scan method are presented. The nonlinear refractive indices of these solutions at the wavelength of the Nd:YAG laser (λ=1064 nm) and its second harmonic (λ=532 nm) were measured. The two-photon absorption of these solutions and their nonlinear susceptibilities were studied.     

二极管激光侧面泵浦腔内倍频Nd：YAG板条激光器研究

用准连续６０Ｗ的二极管激光列阵侧面泵浦“之”字形Ｎｄ：ＹＡＧ板条激光器，当泵浦功率为４５Ｗ，脉宽为４００μｓ时，得到３．５ｍＪ的激光输出。用ＫＤ＊Ｐ电光开关调Ｑ，得到１８ｎｓ（ＦＷＨＭ）、２ｍＪ的脉冲激光输出，用ＫＴＰ晶体作腔内倍频，得到１５ｎｓ、０．８５ｍＪ的二次谐波激光输出。在腔内无调Ｑ元件且腔长小于５ｃｍ时，于近阈值处得到单频绿光输出，而当泵浦功率稍大，腔内有数个纵模振荡时，观察到激光的反相态，并用数值模拟的结果对此作了解释。     

33 W continuous-wave single-frequency green laser by frequency doubling of a single-mode YDFA

A high power continuous-wave single-frequency green fiber laser by second-harmonic generation of a Yb-doped fiber amplifier(YDFA)is developed.A linearly polarized single-mode fiber amplifier produces a 60 W infrared laser at 1064 nm with a 103 W incident diode pump laser at 976 nm,corresponding to an optical conversion efficiency of 58%.An external bow-tie enhancement cavity incorporating a noncritically phase-matched lithium triborate crystal is employed for second-harmonic generation.A 33.2 W laser at 532 nm is obtained with a 45 W incident 1064 nm fundamental laser,corresponding to a conversion efficiency of 74%.     

A comparative study on dual colour soft aperture cascaded second-order mode-locking with different nonlinear optical crystals

A comparative study in terms of optimized output power and stability is made on cascaded second-order nonlinear optical mode-locking with KTP, BBO and LBO crystals for both 1064 nm and 532 nm. Large nonlinear optical phase shift achieved in a non-phase-matched second harmonic generating crystal, is transformed into amplitude modulation through soft aperturing the nonlinear cavity mode variation at the laser gain medium to mode-lock a Nd:YVO4 laser. The laser delivers stable dual wavelength cw mode-locked pulse train with pulse duration 10.3 ps and average power of 1.84 W and 255 mW at 1064 nm and 532 nm respectively for the optimum performance in type-II KTP crystal. The exceptional stability achieved with KTP is accounted by simulating the mode-size variation with phase mismatch.     

Contribution of near infrared laser techniques to the spectroscopic study of black liquids

We present here what we believe to be an original investigation of oil products optical properties (refractive index, fluorescence emission, isotropic and anisotropic Rayleigh scattering) using c.w and Q-switched laser waves in the near infrared (1064 nm). The results obtained show that IR laser techniques can elegantly solve the problem of optical measurements in black liquids and solids.     

可溶性碳纳米管光限幅特性的实验研究

利用实验的方法研究了可溶性碳纳米管对波长为1064和532nm激光的光限幅效应.分析了在 不同的样品浓度、不同的样品厚度情况下可溶性碳纳米管的光限幅特性，并对溶剂也进行了 光限幅实验.实验结果表明，在各种情况下可溶性碳纳米管对1064和532nm激光具有较强的 光限幅特性. 关键词： 可溶性碳纳米管 光限幅效应 强激光防护     

Processing of Diamond for Integrated Optic Devices Using Q-Switched Nd:YAG Laser at Different Wavelengths

In the present investigation, a Q-switched Nd:YAG laser is used to study the various aspects of diamond processing for fabricating integrated optic and UV optoelectronic devices. Diamond is a better choice of substrate compared to silicon and gallium arsenide for the fabrication of waveguides to perform operations such as modulation, switching, multiplexing, and filtering, particularly in the ultraviolet spectrum. The experimental setup of the present investigation consists of two Q-Switched Nd:YAG lasers capable of operating at wavelengths of 1064 nm and 532 nm. The diamond cutting is performed using these two wavelengths by making the “V”-shaped groove with various opening angle. The variation of material loss of diamond during cutting is noted for the two wavelengths. The cut surface morphology and elemental and structural analysis of graphite formed during processing in both cases are compared using scanning electron microscopy (SEM) and laser Raman spectroscopy. Both the Q-Switched Nd:YAG laser systems (at 1064 nm and 532 nm) show very good performance in terms of peak-to-peak output stability, minimal spot diameter, smaller divergence angle, higher peak power in Q-switched mode, and good fundamental TEM₀₀ mode quality for processing natural diamond stones. Less material loss and minimal micro cracks are achieved with wavelength 532 nm whereas a better diamond cut surface is achieved with processing at 1064 nm with minimum roughness.     

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。     

High-quality and high-efficiency machining of glass materials by laser-induced plasma-assisted ablation using conventional nanosecond UV, visible, and infrared lasers

This paper reports the micromachining of fused quartz and Pyrex glass by laser-induced plasma-assisted ablation (LIPAA) using a conventional nanosecond laser at wavelengths 266 nm, 532 nm, and 1064 nm, respectively. High-quality surface structuring can be achieved at each of these wavelengths. The micrograting formed has periods of 14 7m at 266 nm, 20 7m at 532 nm, and 30 7m at 1064 nm, respectively. The ablation rate using a 266 nm laser is much larger than that at longer wavelengths. The ablation thresholds of laser fluence are 0.7 J/cm² for 266 nm, 1.5 J/cm² for 532 nm and 3.7 J/cm² for 1064 nm, respectively. The 532 nm and 1064 nm lasers enable hole drilling in 0.5 and 2.0-mm thick fused quartz and Pyrex glass substrates of about 0.7-0.8 mm in diameter. However, the less destructive through channel can be only formed in Pyrex glass by using a 532 nm laser.