MoS_2溶液的波长选择性光限幅效应研究

采用N,N-二甲基甲酰胺(DMF)和四氢呋喃(THF)为溶剂,用离散法制备二硫化钼(MoS2)悬浮溶液,并用开孔Z扫描方法研究其在可见和近红外区域的非线性光学特性.结果显示,在强激光照射下,MoS2(in THF)悬浮溶液在可见波段(530 nm)透过率增强为常光透过率的1.54倍,表现为饱和吸收;在近红外波段(790 nm)透过率减弱为常光透过率的0.6倍,表现为反饱和吸收,具有很好的波长选择性光限幅效应.而作为对比的MoS2(in DMF)悬浮溶液在全波段透过率降低,呈现反饱和吸收特性,波长选择性不明显.机理解释可能为饱和吸收和热效应导致的自衍射两种机制联合作用.     

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.     

Theoretical Analysis of Photon-Mode Super-Resolution Optical Memory Using Saturable Absorption Dye

The possibility of a super-resolution optical memory using a saturable absorption dye mask layer is theoretically discussed. An equation which estimates the transmittance change of the mask layer has been derived. The numerical simulation shows that an efficient super-resolution is performed when the initial optical density of the mask layer is high.     

足球烯分子C_(60)及C_(70)的反饱和吸收性质与光限制效应

报道了对足球烯分子纯C_60及纯C_70的光限制效应的研究结果,讨论了样品的浓度及三重态寿命对光限制阈值的影响.首次报道在足球稀分子中发现的三重态吸收饱和现象,并阐述了其产生的原因及对光限制效应的影响.     

光学元件波前畸变对驱动器光路设计的影响

高功率激光驱动器光路设计要考虑像传递、鬼像规避和杂散光管理等多项优化措施.基于衍射光学传播理论,从输出负载能力提升的角度研究大口径光学元件波前特性对驱动器光路设计参数优化的影响.研究表明,驱动器末级光路的排布间隔如果控制在6 m以上,将非常有助于提高激光驱动器的输出负载能力.一般情况下,波前峰谷值达到0.34λ的单块大口径光学元件能使高功率激光的近场光束质量最大下降约10%,达到1.36λ后最大下降约21%;波前分布特性不同的多片大口径光学元件的波前相消叠加有利于降低中频波前部分对装置负载能力的影响,但是,大口径光学元件的非线性效应会加重中频波前对装置输出负载能力的影响;在限定大口径元件损伤阈值20J/cm~2的前提下,光路排布紧凑的激光驱动器末级输入激光通量控制在16.8J/cm~2之下不易损伤光学元件.相对宽松的光路设计可以进一步提高末级输出激光的平均通量水平,非常有利于激光驱动器装置输出负载能力的提升.     

Tailoring optical properties of TiO2 in silica glass for limiting applications

We present the linear and nonlinear optical studies on TiO2-SiO2 nanocomposites with varying compositions. Opti- cal band gap of the material is found to vary with the amount of SiO2 in the composite. The phenomenon of two-photon absorption （TPA） in TiO2/SiO2 nanocomposites has been studied using open aperture Z-scan technique. The nanocom- posites show better nonlinear optical properties than pure TiO2, which can be attributed to the surface states and weak dielectric confinement of TiO2 nanoparticles by SiO2 matrix. The nanocomposites are thermally treated and similar studies are performed. The anatase form of TiO2 in the nanocomposites shows superior properties relative to the amorphous and rutile counterpart. The involved mechanism is explained by rendering the dominant role played by the excitons in the TiO2 nanoparticles.     

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。     

Topological insulator as an optical modulator for pulsed solid‐state lasers

Topological insulators are states of quantum matter that have narrow topological nontrivial energy gaps and a large third‐order nonlinear optical response. The optical absorption of topological insulators can become saturated under strong excitation. In this work, with Bi₂Se₃ as an example, it was demonstrated that a topological insulator can modulate the operation of a bulk solid‐state laser by taking advantage of its saturable absorption. The result suggests that topological insulators are potentially attractive as broadband pulsed modulators for the generation of short and ultrashort pulses in bulk solid‐state lasers, in addition to other promising applications in physics and computing.     

反饱和特性化合物锌四苯并卟吩巴豆酸苯氧树脂的光吸收谱测定

报道一种新型的有机材料锌—四苯并叶吩—巴豆酸—苯氧树脂(缩写为Zntbp—CA—PhR)体系薄膜样品的吸收谱的测定，及其主要吸收谱带在激光作用下的变化情况及动力学过程。实验观察到此种材料显著的饱和及反饱和吸收现象，并观察到它的再反饱和过程，定性分析了变化过程中的物理机制。这种特征在可见光波段一个较宽的区域内都会出现。所获结果为此种有机材料在光谱域信息存储和光学限制等方面的应用提供了理论和实验依据。     

碳纳米管/二硒化钼有机玻璃的非线性吸收、非线性散射和光限幅特性

MoSe₂的禁带宽度较窄（1.1–1.5 eV）,且具有可调谐的激子光电效应,这样使其在光致发光、光电晶体管、太阳能电池和光学非线性等方面具有潜在的应用价值.然而,纯的MoSe₂的光生电子空穴复合率较高,限制了其在某些光学领域中的应用.通过设计MoSe₂的复合材料,可以降低材料的光生电子空穴复合率,从而扩展其应用领域.首先,通过热溶剂法合成CNT/MoSe₂复合材料;然后,通过浇铸法将其分散在甲基丙烯酸甲酯（MMA）中制备成有机玻璃,其中MMA会聚合成聚甲基丙烯酸甲酯（PMMA）,并利用改进的Z-扫描技术首次对CNT/MoSe₂/PMMA有机玻璃的非线性吸收、非线性散射和光限幅特性进行了研究.研究表明,随着输入能量的变化,通过调节输入能量,CNT/MoSe₂/PMMA有机玻璃表现出饱和吸收（SA）和从SA到反饱和吸收的转变.结合材料特性及应用条件要求,可以得到CNT/MoSe₂/PMMA有机玻璃在光学设备,如光学限制器和锁模/调Q激光器等方向具有较好的应用前景.     

覆盖可见光波长的掺Er光纤飞秒光学频率梳

飞秒光学频率梳波长覆盖范围向可见光波长扩展对于碘稳频激光的绝对频率测量以及光钟研究中钟激光的绝对频率测量都具有十分重要的意义. 本文在自行研制掺Er光纤飞秒光学频率梳的基础上, 采用放大-倍频-扩谱的方案, 实现了激光输出波长向可见光波长的扩展. 掺Er光纤飞秒光学频率梳输出的一部分光激光脉冲, 功率约为8 mW, 首先经掺Er光纤放大器将功率提高到531 mW, 此后利用MgO: PPLN晶体倍频, 倍频后激光的功率为170 mW, 倍频效率为32%, 脉冲宽度为85 fs. 倍频后的激光通过光子晶体光纤进行光谱展宽. 通过优化入射光偏振状态可以实现波长覆盖500-1000 nm, 输出功率为85 mW, 耦合效率为50%. 采用小型化碘稳频532 nm Nd: YAG激光器输出激光与光学频率梳光谱展宽后的激光进行拍频可以获得30 dB的拍频信号. 覆盖可见光波长的掺Er光纤飞秒光学频率梳为可见光范围内激光的绝对频率测量提供了技术手段.     

Z-scan studies and optical limiting of nanosecond laser pulses in neutral red dye

The nonlinear optical absorption, refraction and optical limiting behaviour of an organic dye, neutral red, were investigated under excitation with nanosecond laser pulses at 532 nm. The nonlinear optical responses of the material were studied both in solution and solid film, made in methanol and polyvinyl alcohol, respectively, using single-beam Z-scan technique. The open aperture Z-scans of the solution samples displayed a switch over from saturable absorption to enhanced absorption with increase in input intensity. Theoretical fit to the experimental data indicated that the dominant mechanism of nonlinear absorption is two-photon absorption. The closed aperture Z-scans of both the samples denoted positive nonlinearity, which was three orders larger in magnitude in solid film, compared with that in solution. The results of optical limiting experiments revealed that neutral red exhibited strong optical limiting of nanosecond laser pulses with a threshold lower than that of C₆₀ in toluene.     

多元纳米稀土六硼化物Nd1-xEuxB6粉末的制备及光吸收研究

在真空环境中采用固相烧结法成功制备出了多元稀土六硼化物Nd1-xEuxB6纳米粉末.系统研究了Eu掺杂对纳米NdB6物相、形貌及光吸收性能的影响规律.结果表明,所有合成的纳米粉末物相均为单相的CsCl型晶体结构,具有立方形貌,平均晶粒尺度为30 nm.光吸收实验结果表明,随着Eu掺杂量的增加,纳米NdB6透射光波长从629 nm红移至1000 nm以上,表现出了透射光波长的可调特性.此外,NdB6和EuB6同步辐射吸收图谱表明,Nd和Eu原子分别以Nd^3+和Eu^2+形式存在于纳米NdB6和EuB6中,充分说明了Eu掺杂使NdB6传导电子数量减少,从而导致其等离子共振频率能量的降低.采用第一性原理计算了NdB6和EuB6的能带结构、态密度、介电函数以及等离子共振频率能量,从而定性解释了Eu掺杂使NdB6透射光波长红移的特性.     

W型单模单偏振光纤基模截止的条件

给出了 W型单模单偏振光纤基模截止的必要条件。通过对基模截止波长的数值计算 ,分析了这个必要条件的充分性。结论是 :对于圆形内包层 W型光纤来说 ,这是必要的而又充分的条件 ;对于低椭圆度内包层 W型单模单偏振光纤来说 ,它可以在较高的精度上近似作为充分条件 ,而对于高椭圆度内包层 W型单模单偏振光纤来说 ,它仅仅只是必要条件而非充分条件     

Simultaneous estimation of optical nonlinear refractive and absorptive parameters by solvent induced changes in optical density

With picosecond pulses at the wavelength of 532 nm, we have determined the optical nonlinear refractive and absorptive parameters of the dye N,N′-bis(2,5-di-tert-butylphenyl)-3,4,9,10-perylenedicarboximide (DBPI) by a single closed-aperture (CA) Z-scan technique. This technique uses a theoretical model that elucidates the refractive and absorptive optical nonlinearity present simultaneously in the CA Z-scan profile. The observed remarkable red shift in the absorption spectrum of the dye in the acidic medium as compared to that in the polar medium has been used to vary the optical density at a single frequency. We find that the effect of saturable absorption (SA) is complete at higher concentrations. The effect of reverse saturable absorption (RSA) is dominating in dilute concentrations. The observed variations in the excited state refractive cross-section (σ_r) with the concentration and the energy have been attributed to the contributions of higher order nonlinearity along with the existing third-order nonlinearity.     

硫化锡电子结构和光学性质的量子尺寸效应

基于密度泛函理论的第一性原理计算,系统研究了硫化锡(SnS)晶体、纳米单层及多层的结构稳定性、电子结构和光学性质.结果表明:由于相对弱的层间范德瓦尔斯力作用,SnS单层纳米片可以像石墨烯等二维材料一样从块体中剥离出来;受制于量子尺寸效应和层间相互作用的影响,SnS的结构稳定性随层数减少而逐渐减弱,其带隙随层数减少而逐渐增大;由于材料的本征激发和吸收取决于电子结构,因此改变SnS材料的层数可以到达调控其光学性质的目的;SnS块体和纳米结构的主要光学吸收峰起源于Sn-5s,5p和S-2p轨道之间的电子跃迁;并且从块体到单层纳米结构,SnS的光学吸收峰出现明显的蓝移.本文的研究将有助于SnS材料在太阳能电池领域的应用.     

硅基有机太阳能电池光学性能分析

采用传输矩阵法的光学模型以及MATLAB软件模拟了硅基有机太阳能电池对入射光的吸收率和各层厚度的关系。模拟表明活性层对入射光的吸收率主要受其自身厚度影响,且由于微腔效应,这种结构的电池可以很大程度上优化活性层厚度;另外通过调节折射率匹配层厚度和传输层厚度也可以优化活性层对入射光的吸收率。在本文所讨论的厚度中,最佳传输层厚度为10 nm左右,最佳匹配层厚度为30 nm ZnS或者60 nm Alq₃。     

基于双光路原理的海水IOPs高光谱测量仪方案

设计了基于双光路原理的海水固有光学参数测量仪。该仪器可同步测量水体光谱吸收系数a、光束衰减系数c和体散射系数b。其中吸收系数a采用反射式吸收管测量,光束衰减系数c采用全吸收式样品池测量,体散射系数b根据c=a+b计算。光信号由光纤收集、光谱仪分光后用CCD探测器测量。光谱分辨率为4nm,灵敏度为0 001m-1。该仪器直接在水下工作,由水泵抽取被测海水,水下最大工作深度为200m。测量数据可以自动记录,同时也可以通过水下电缆实时传输到调查船实验室。     

Wavelength conversion in optical transport networks

The introduction of optical technology in the path layer of a transport network is analyzed; in particular, the impact of all-optical wavelength conversion is examined. Two basic optical cross-connect schemes based on space switching and on wave-length switching, respectively, and two types of wavelength converters are considered. The wavelength converters are, respectively, based on four-wave miring (FWM) in semiconductor optical amplifiers (SOAs) and on cross-phase modulation (XPM) obtained by two SOAs put in an interferometric configuration. An analysis of transmission performances of optical transport networks employing both types of wavelength conversion and both the node architectures is reported. The performances are evaluated by means of a system modeling that facilitates considering physical phenomena occurring during transmission and all the important transmission impairments. The analysis reveals that both the types of converters can be employed with different features and limitations, according to the considered network and switching architecture.     

Numerical study of converting beat-note signals of dual-frequency lasers to optical frequency combs by optical injection locking of semiconductor lasers

The optical injection locking of semiconductor lasers to dual-frequency lasers is studied by numerical simulations. The beat-note signals can be effectively transformed to optical frequency combs due to the effective four wave-mixing in the active semiconductor gain medium. The low-noise Gaussian-like pulse can be obtained by locking the relaxation oscillation and compensating the gain asymmetry. The simulations suggest that pulse trains of width below 30 ps and repetition rate in GHz frequency can be generated simply by the optical injection locking of semiconductor lasers. Since the optical injection locking can broaden the spectrum and amplify the optical power simultaneously, it can be a good initial stage for generating optical frequency combs from dual-frequency lasers by multi-stage of spectral broadening in nonlinear waveguides.