共查询到20条相似文献,搜索用时 15 毫秒
1.
Photoinduced optical phenomena in SiC nanocrystallites embedded within the photo-polymer oligoetheracrylate matrices have been studied using experimental nonlinear optics, particularly photoinduced optical second harmonic generation (SHG). The YAG-Nd-laser (λ=1.06 μm; W=30 MW; pulse duration within the 30–50 ps) was used as a source of pumping light and the nitrogen laser (λ=337 nm) has been applied as a source of the photoinducing light. With increasing intensity of the photoinducing beam, the SHG (λ=0.53 μm) signal increased and achieved a maximum (χ222=10.1 ± 0.13 pm/V) at a photon flux of about 1.61 GW/cm2. With decreasing temperature, the SHG signal strongly increases within the temperature range 25–30 K. Time-dependent probe–pump measurements indicate an existence of the SHG maximum for a pump–probe time delay of about 20 ps. The SiC hexagonal structural components play a key role in the observed photoinduced nonlinear optical effects. Large values of the nonlinear optical constants as well the good technological parameters open a possibility to enhance the nonlinear optical susceptibilities. 相似文献
2.
Novel nonlinear optical (NLO) building blocks can be placed into the periphery, branch, or core of a dendrimer to construct precise molecular architecture with predetermined chemical composition. The site‐isolation effect, through the encapsulation of active moieties by dendrons, or the cooperative effect, through the coherent interaction among the same or different kinds of active blocks in the dendrimer, can greatly enhance the performance of NLO materials. This paper provides a review of recent developments in dendrimers for NLO applications, such as electro‐optics (E‐O), photorefractive (PR) materials, second harmonic generation (SHG), and two‐photon absorption (TPA). 相似文献
3.
Zheng Zheng Dongyu Li Zhiyang Liu Hui‐Qing Peng Herman H. Y. Sung Ryan T. K. Kwok Ian D. Williams Jacky W. Y. Lam Jun Qian Ben Zhong Tang 《Advanced materials (Deerfield Beach, Fla.)》2019,31(44)
Nonlinear optical microscopy has become a powerful tool in bioimaging research due to its unique capabilities of deep optical sectioning, high‐spatial‐resolution imaging, and 3D reconstruction of biological specimens. Developing organic fluorescent probes with strong nonlinear optical effects, in particular third‐harmonic generation (THG), is promising for exploiting nonlinear microscopic imaging for biomedical applications. Herein, a simple method for preparing organic nanocrystals based on an aggregation‐induced emission (AIE) luminogen (DCCN) with bright near‐infrared emission is successfully demonstrated. Aggregation‐induced nonlinear optical effects, including two‐photon fluorescence (2PF), three‐photon fluorescence (3PF), and THG, of DCCN are observed in nanoparticles, especially for crystalline nanoparticles. The nanocrystals of DCCN are successfully applied for 2PF microscopy at 1040 nm NIR‐II excitation and THG microscopy at 1560 nm NIR‐II excitation, respectively, to reconstruct the 3D vasculature of the mouse cerebral vasculature. Impressively, the THG microscopy provides much higher spatial resolution and brightness than the 2PF microscopy and can visualize small vessels with diameters of ≈2.7 µm at the deepest depth of 800 µm in a mouse brain. Thus, this is expected to inspire new insights into the development of advanced AIE materials with multiple nonlinearity, in particular THG, for multimodal nonlinear optical microscopy. 相似文献
4.
X. M. Chen M. Oyama M. Reben A. Wojciechowski N. AlZayed A. O. Fedorchuk I. V. Kityk 《Journal of Materials Science: Materials in Electronics》2013,24(11):4204-4208
It is reported that there is substantial enhancement of the optical second harmonic generation (SHG) at 1064 nm Nd:YAG laser wavelength for LiB3O5 nanocrystatllites embedded into the electric field aligned photopolymer oligoetheracrylate matrices. The borate nanocomposite was put between the electrodes containing Ag/ZnO NP with silver sizes 20, 40 and 60 nm. We study an influence of the Ag NP sizes on the output SHG. It is clearly seen that only excitation by the green continuous wave 532 nm laser with power about 350–400 mW with beam diameter about 4 mm give significant effect. The latter confirms a principal role of the surface plasmon resonances spectrally overlapped with the nonlinear excitations responsible for the observed changes of the SHG. 相似文献
5.
Fernanda Ramos‐Gomes Wiebke Mbius Luigi Bonacina Frauke Alves Marietta Andrea Markus 《Small (Weinheim an der Bergstrasse, Germany)》2019,15(4)
Recently, second harmonic generation (SHG) nanomaterials have been generated that are efficiently employed in the classical (NIR) and extended (NIR‐II) near infrared windows using a multiphoton microscope. The aim was to test bismuth ferrite harmonic nanoparticles (BFO‐HNPs) for their ability to monitor pulmonary macrophages in mice. BFO‐loaded MH‐S macrophages are given intratracheally to healthy mice or BFO‐HNPs are intranasally instilled in mice with allergic airway inflammation and lung sections of up to 100 μM are prepared. Using a two‐photon‐laser scanning microscope, it is shown that bright BFO‐HNPs signals are detected from superficially localized cells as well as from deep within the lung tissue. BFO‐HNPs are identified with an excellent signal‐to‐noise ratio and virtually no background signal. The SHG from the nanocrystals can be distinguished from the endogenous collagen–derived SHG around the blood vessels and bronchial structures. BFO‐HNPs are primarily taken up by M2 alveolar macrophages in vivo. This SHG imaging approach provides novel information about the interaction of macrophages with cells and the extracellular matrix in lung disease as it is capable of visualizing and tracking NP‐loaded cells at high resolution in thick tissues with minimal background fluorescence. 相似文献
6.
Plasmonic nanostructures enable the generation of large electromagnetic fields confined to small volumes, potentially providing a route for the development of nanoengineered nonlinear optical media. A metal-capped hemispherical nanoparticle, also known as a nanocup, generates second harmonic light with increasing intensity as the angle between the incident fundamental beam and the nanocup symmetry axis is increased. Nanoparticle orientation also modifies the emission direction of the second harmonic light. With conversion efficiencies similar to those of inorganic SHG crystals, these structures provide a promising approach for the design and fabrication of stable, synthetic second-order nonlinear optical materials tailored for specific wavelengths. 相似文献
7.
Yuqiang Fang Xin Feng Dong Wang Yang Ding Tianquan Lin Tianyou Zhai Fuqiang Huang 《Small (Weinheim an der Bergstrasse, Germany)》2023,19(26):2207934
Second harmonic generation (SHG) of 2D crystals has been of great interest due to its advantages of phase-matching and easy integration into nanophotonic devices. However, the polarization-dependence character of the SHG signal makes it highly troublesome but necessary to match the laser polarization orientation relative to the crystal, thus achieving the maximum polarized SHG intensity. Here, it is demonstrated a polarization-independent SHG, for the first time, in the van der Waals Nb3SeI7 crystals with a breathing Kagome lattice. The Nb3 triangular clusters and Janus-structure of each Nb3SeI7 layer are confirmed by the STEM. Nb3SeI7 flake shows a strong SHG response due to its noncentrosymmetric crystal structure. More interestingly, the SHG signals of Nb3SeI7 are independent of the polarization of the excitation light owing to the in-plane isotropic arrangement of nonlinear active units. This work provides the first layered nonlinear optical crystal with the polarization-independent SHG effect, providing new possibilities for nonlinear optics. 相似文献
8.
The process of second harmonic generation (SHG) has a unique property of forming a sharp optical contrast between noncentrosymmetric crystalline materials and other types of material, which is a highly valuable asset for contrast microscopy. The coherent signal obtained through SHG also allows for the recording of holograms at high spatial and temporal resolution, enabling whole-field four-dimensional microscopy for highly dynamic microsystems and nanosystems. Here we describe a new holographic principle, harmonic holography (H(2)), which records holograms between independently generated second harmonic signals and reference. We experimentally demonstrate this technique with digital holographic recording of second harmonic signals upconverted from an ensemble of second harmonic generating nanocrystal clusters under femtosecond laser excitation. Our results show that harmonic holography is uniquely suited for ultrafast four-dimensional contrast microscopy. 相似文献
9.
Qiang Wang Xue-Hua Dong Ling Huang Kang-Min Ok Zhi-En Lin Guo-Hong Zou 《Small (Weinheim an der Bergstrasse, Germany)》2023,19(39):2302797
Oxides are emerging candidates for mid-infrared (mid-IR) nonlinear optical (NLO) materials. However, their intrinsically weak second harmonic generation (SHG) effects hinder their further development. A major design challenge is to increase the nonlinear coefficient while maintaining the broad mid-IR transmission and high laser-induced damage threshold (LIDT) of the oxides. In this study, it is reported on a polar NLO tellurite, Cd2Nb2Te4O15 (CNTO), featuring a pseudo-Aurivillius-type perovskite layered structure composed of three types of NLO active groups, including CdO6 octahedra, NbO6 octahedra, and TeO4 seesaws. The uniform orientation of the distorted units induces a giant SHG response that is ≈31 times larger than that of KH2PO4, the largest value among all reported metal tellurites. Additionally, CNTO exhibits a large band gap (3.75 eV), a wide optical transparency window (0.33–14.5 µm), superior birefringence (0.12@ 546 nm), high LIDT (23 × AgGaS2), and strong acid and alkali resistance, indicating its potential as a promising mid-IR NLO material. 相似文献
10.
Mohammad Taghinejad Zihao Xu Hua Wang Hossein Taghinejad Kyu‐Tae Lee Sean P. Rodrigues Ali Adibi Xiaofeng Qian Tianquan Lian Wenshan Cai 《Small (Weinheim an der Bergstrasse, Germany)》2020,16(5)
Atomically thin transition metal dichalcogenides (TMDs) in their excited states can serve as exceptionally small building blocks for active optical platforms. In this scheme, optical excitation provides a practical approach to control light‐TMD interactions via the photocarrier generation, in an ultrafast manner. Here, it is demonstrated that via a controlled generation of photocarriers the second‐harmonic generation (SHG) from a monolayer MoS2 crystal can be substantially modulated up to ≈55% within a timeframe of ≈250 fs, a set of performance characteristics that showcases the promise of low‐dimensional materials for all‐optical nonlinear data processing. The combined experimental and theoretical study suggests that the large SHG modulation stems from the correlation between the second‐order dielectric susceptibility χ(2) and the density of photoexcited carriers in MoS2. Indeed, the depopulation of the conduction band electrons, at the vicinity of the high‐symmetry K/K′ points of MoS2, suppresses the contribution of interband electronic transitions in the effective χ(2) of the monolayer crystal, enabling the all‐optical modulation of the SHG signal. The strong dependence of the second‐order optical response on the density of photocarriers reveals the promise of time‐resolved nonlinear characterization as an alternative route to monitoring carrier dynamics in excited states of TMDs. 相似文献
11.
Jianhua Xu Xingze Lu Hongbing Chen Liying Liu Wencheng Wang Congshan Zhu Fuxi Gan 《Optical Materials》1997,8(4):243-247
The influence of electric of poling conditions on the optical nonlinearity of fused silica has been investigated by the second harmonic generation (SHG) technique. The SHG intensity of the poled fused silica increased monotonically with increasing the poling voltage or poling time, and reached a maximum at a poling temperature of T = 250°C, but the SHG intensity decreased quickly as the thermal erasure time increased. The experimental results have been explained using an electric field induced dipole orientation model. 相似文献
12.
《Journal of Experimental Nanoscience》2013,8(1):104-113
ABSTRACTIn this study, it was shown that field enhancement in the nonlinear metal-insulator-metal (MIM) plasmonic waveguides can result in a large enhancement of the second harmonic generation (SHG) magnitude as compared with values reported in the literature. The proposed structure has two metals at the top and two metals at the bottom of the crystal. In this structure, a voltage is applied on metals to produce a SHG electrically. Hence, the metals that define the cavity also serve as electrodes capable of generating high direct current electric fields across the nonlinear material. The frequency of a fundamental wave at 458 nm was doubled and modulated in intensity by applying a moderate external voltage to the electrodes, yielding a voltage-dependent nonlinear generation with a higher coupling efficiency. All the simulations here have been calculated by using the finite-element-based commercial COMSOL software. 相似文献
13.
二次谐波作为非线性光学的重要分支,逐渐成为表征晶体结构的重要手段之一。在众多表征方法中,二次谐波因其无损检测、高稳定性、可调谐性、超快响应、偏振敏感性、通用性、操作简单等特点被广泛应用于二维材料结构表征,为二维材料的物性研究和功能应用提供了重要信息,大大推动了二维材料基础研究的快速发展。本文综述了近几年二次谐波在二维材料结构表征中的研究,简述了二次谐波产生原理,介绍了飞秒激光器接入共聚焦拉曼光谱仪产生二次谐波测试装置,分别讨论了二次谐波在二维材料的层间堆垛层数、层间堆垛角度、单层二维材料晶界及晶体取向表征方面的应用。同时,本文还介绍了采用二次谐波强度直接、灵敏地检测晶体中应变幅度以及通过二次谐波信号变化跟踪材料中的缺陷变化,接着讨论了二次谐波与拉曼光谱、光致发光的多维度关联分析在材料全面深度表征方面的重要性。最后展望了二次谐波未来在材料结构表征中的潜在研究方向。 相似文献
14.
Max Burian Carina Karner Maksym Yarema Wolfgang Heiss Heinz Amenitsch Christoph Dellago Rainer T. Lechner 《Advanced materials (Deerfield Beach, Fla.)》2018,30(32)
When nanocrystals self assemble into ordered superstructures they form functional solids that may inherit the electronical properties of the single nanocrystals. To what extent these properties are enhanced depends on the positional and orientational order of the nanocrystals within the superstructure. Here, the formation of micrometer‐sized free‐standing supercrystals of faceted 20 nm Bi nanocrystals is investigated. The self‐assembly process, induced by nonsolvent into solvent diffusion, is probed in situ by synchrotron X‐ray scattering. The diffusion‐gradient is identified as the critical parameter for controlling the supercrystal‐structure as well as the alignment of the supercrystals with respect to the substrate. Monte Carlo simulations confirm the positional order of the nanocrystals within these superstructures and reveal a unique orientation phase: the nanocrystal shape, determined by the atomic Bi crystal structure, induces a total of 6 global orientations based on facet‐to‐facet alignment. This parallel alignment of facets is a prerequisite for optimized electronic and optical properties within designed nanocrystal solids. 相似文献
15.
A. A. Umar Ali H. Reshak M. Oyama K. J. Plucinski 《Journal of Materials Science: Materials in Electronics》2012,23(2):546-550
The study of photoluminescence and nonlinear optical properties of red (emitted at 650 nm), yellow (emitted at 570 nm) and
green (emitted at 530 nm) CdTe quantum dots (QD) spin coated on quartz substrate that had been prepared by changing the ratio
between octadecylphosphonic acid and octadecence within 0.1:1–1:1 was carried out. Spectral width of the emission spectra
indicates an enhancement with the increasing of QDs sizes, namely ca. 25, 28 and 50 nm for the QD size of 2.5, 3.5 and 5 nm,
correspondingly. The entire QDs samples feature a spherical morphology with a relatively narrow size distribution. The optical
second harmonic generation (SHG) stimulated by coherent bicolor treatment at 1,540 nm and its second harmonic generation was
studied versus the laser light power density and incident angle. 相似文献
16.
Rihong Cong Tao Yang Fuhui Liao Yingxia Wang Zheshuai Lin Jianhua Lin 《Materials Research Bulletin》2012,47(9):2573-2578
The structural characteristics and optical properties of bismuth nitrate Bi2O2[NO3(OH)] (BINO) are investigated by experimental in combination with theoretical studies. The BINO crystal was obtained from the hydrothermal growth, and its UV–Vis absorption spectrum was measured. Second harmonic generation (SHG) experiments on powder sample show that BINO is a phase-matchable nonlinear optical crystal with a large powder SHG coefficient of 2.3 pm/V, which is confirmed by the first-principles calculations. Moreover, the structural origin of nonlinear optical effects in BINO is given. Our studies reveal that BINO is a promising SHG crystal in the visible and infrared spectral region. 相似文献
17.
采用水热法合成出一种新型碳酸盐非线性光学晶体材料KNa5Ca5(CO3)8, 该晶体属于六方晶系, 空间群为P63mc, 晶胞参数为a=b=1.00786(4) nm, c=1.26256(8) nm, Z=2。其晶体结构可以看作是由站立的[CO3]基团连接相邻的两个[CaCO3]∞层, 从而沿[010]方向形成了四种不同类型的孔洞, 在这些孔洞中填充着K、Na 和[Na0.67Ca0.33]原子。KNa5Ca5(CO3)8晶体的粉末倍频效应为KDP的1.2倍, 且能够在可见光区实现相位匹配。紫外-可见-近红外漫反射光谱测试结果表明其晶体具有较大的光学带隙, 大概为5.95 eV, 是具有潜在应用前景的紫外非线性光学晶体材料。此外, 第一性原理的计算结果表明, 晶体的非线性系数主要来源于CO3基团。 相似文献
18.
We have synthesized and characterized three types of perovskite alkaline niobate nanowires: NaNbO(3), KNbO(3), and LiNbO(3) (XNbO(3)). All three types of nanowires exhibit strong nonlinear response. Confocal imaging has been employed to quantitatively compare the efficiency of synthesized nanowires to generate second harmonic signal and to show that LiNbO(3) nanowires exhibit the strongest nonlinear response. We also investigated the polarization response of the second harmonic generation (SHG) signal in all three types of alkaline nanowires for the two geometries tractable by our optical trapping setup. The SHG signal is highly influenced by the nanowire crystallinity and experimental geometry. We also demonstrate for the first time wave-guiding of SHG signal in all three types of alkaline niobate nanowires. By carefully examining nonlinear properties of (XNbO(3)) nanowires we suggest which type of wires are best suited for the given application. 相似文献
19.
K. A. Brekhov K. A. Grishunin N. A. Ilyin A. P. Shestakova S. D. Lavrov E. D. Mishina 《Technical Physics Letters》2017,43(12):1112-1114
WSe2 films have been studied by the method of second harmonic generation (SHG) in the 1200–1420 nm wavelength range at room temperature. Preliminary investigations of photoluminescence spectra and atomic force microscopy showed that the film consists of extended microcrystals and has a thickness of about 1 nm, which corresponds to a single monolayer. The SHG intensity spectrum showed the presence of a 1s (B)-exciton for 1.95-eV photon energy. 相似文献
20.
Xianmen He Lu Qi Wenyao Zhang Ruixin Zhang Xiaoyu Dong Junhong Ma Maierhaba Abudoureheman Qun Jing Zhaohui Chen 《Small (Weinheim an der Bergstrasse, Germany)》2023,19(18):2206991
Regulating the crystal structure by A-site cation substitution is one of the effective methods to explore high-performance nonlinear optical (NLO) materials. Herein, two non-centrosymmetric (NCS) compounds, α-MZnPO4 (M = Li, K) with short UV absorption edges 221 and 225 nm, are obtained by performing A-site cation substitution method. It is noteworthy that α-LiZnPO4 (α-LZPO) achieves >10 times second harmonic generation (SHG) response (2.3 × KDP) enhancement compared with that of α-KZnPO4 (α-KZPO) (0.2 × KDP), which is the only case among phosphates with different A-site cations. By structural comparison, it is found that the A-site cations play important roles for anion rearrangements, and further the structure features of the two compounds by designing two suppositional crystal models as well as performing other theoretical calculations are analyzed. The study confirms the feasibility to design promising NLO materials with strengthen SHG response and structural stability in orthophosphate system. 相似文献