Three-dimensional optical data storage using third-harmonic generation in silver zinc phosphate glass

We demonstrate the possibility of three-dimensional optical data storage inside a specific zinc phosphate glass containing silver by using third-harmonic generation (THG) imaging. Information is stored inside the glass with femtosecond laser irradiation below the refractive index modification threshold. We use the same laser for THG readout. The capability of storage with this technique is discussed.     

Third-harmonic generation in relative-phase-controlled two-color laser field

We experimentally demonstrate third-harmonic generation (THG) by intense femtosecond laser pulse at a central wavelength of ??800?nm superposed by its second harmonic in air. The third-harmonic signal shows a periodic modulation with a period of ??0.67?fs when the delay between fundamental and second-harmonic wave is continuously changed. The periodic modulation of THG can be attributed to the interference of third-harmonic signals generated from a direct THG channel (3??=??+??+??) and a four-wave mixing (FWM) channel (3??=2??+2?????). With high pump intensity, the fitting of the measured TH spectrum as a function of delay implies that the pump pulse undergoes a strong pulse splitting and self-phase modulation at the focus.     

Polaron effects on third-harmonic generation in cylindrical quantum-well wires

Polaron effects on third-harmonic generation (THG) in cylindrical quantum wires with a finite confining potential are investigated. The THG coefficient is obtained by using the compact-density-matrix approach and an iterative method, and the numerical results are presented for GaAs/AlAs cylindrical quantum wires. The results show that the THG coefficient is greatly enhanced and the peak shift to the aspect of high energy when considering the influence of electron-phonon interaction.     

Polaron effects on the third-harmonic generations in cylindrical quantum dots

The effect of the electron–LO-phonon interaction on the third-harmonic generation (THG) coefficient for cylinder quantum dots with an applied electric field is theoretically investigated, the THG coefficient is obtained by using compact-density-matrix approach and iterative method, and the numerical results are presented for a GaAs cylinder quantum dots. The results show that the THG coefficient is greatly enhanced and the peak shift to the aspect of high energy when considering the influence of electron–LO-phonon interaction.     

纳米银与表面吸附荧光素的荧光性能的影响

研究了纳米银粒子对表面吸附荧光素(fluorescein,Fl)的荧光性能的影响。Fl溶液中加入纳米银粒子,Fl分子包覆在纳米银粒子表面形成Fl_n-Ag复合物使纳米银相互桥连形成类似网络的结构,且Fl分子吸收峰随着纳米银浓度的增加发生红移。纳米银通过产生的强局域场将能量传输给Fl发光中心,实现了Fl的荧光增强,荧光增强效率随着纳米银浓度的增加具有最大值。较大粒径的纳米银使Fl获得最大荧光增强效率所需浓度较低且最大荧光增强效率值较高。研究结果表明,纳米银与Fl间的能量传输主要由Fl分子附近局域电磁场增强和分子到金属表面无辐射跃迁能量转移过程所决定并与纳米银的浓度、尺寸密切相关。     

Third-harmonic generation in cylindrical parabolic quantum wires with static magnetic fields

The third-harmonic generation (THG) and its conversion efficiency in Al_xGa_1-xAs/GaAs cylindrical parabolic quantum wires with static magnetic fields are studied in detail. The calculated results show that the parabolic confining potential and the static magnetic field have evident influence on the THG and its conversion efficiency. In addition, the conversion efficiency of the THG is also related to the input optical intensity. It is noted that very high conversion efficiency of the THG can be obtained by increasing properly the input optical intensity and choosing an optimized parabolic confining potential and applied static magnetic field.     

Laser fabrication of periodic microstructures from silver nanoparticles in polymer films

The fabrication of photoand thermostable periodic structures from silver nanoparticles in polymer plates (cross-linked oligourethanemethacrylate impregnated with silver precursors Ag(hfac) and Ag(fod) dissolved in the supercritical carbon dioxide) is studied. The process is based on the local (depending on the irradiated spot size) photochemical decomposition of the silver precursors in the polymer matrix that initiates the atomic aggregation and creation of silver nanoparticles with the plasmon resonance in absorption in the spectral range 420–430 nm. The third-harmonic radiation of a Nd:YAG laser (355 nm) and the Kr⁺-laser (521 nm) radiation are employed for the recording of periodic structures with submillimeter and micron resolutions. The photosensitivity of the polymer matrices impregnated with the silver precursors to the UV and visible radiation is discussed.     

Parity-forbidden excitations of Sr(2)CuO(2)Cl(2) revealed by optical third-harmonic spectroscopy

We present the first study of nonlinear optical third-harmonic generation (THG) in the strongly correlated charge-transfer insulator Sr(2)CuO(2)Cl(2). For fundamental excitation in the near infrared, the THG spectrum reveals a strongly resonant response for photon energies near 0.7 eV. Polarization analysis reveals this novel resonance to be only partially accounted for by three-photon excitation to the optical charge-transfer exciton, and indicates that an even-parity state at 2 eV, with a(1g) symmetry, participates in the third-harmonic susceptibility.     

Parameter-dependent third-order optical nonlinearity in a CdSe/ZnS quantum dot quantum well in the vicinity of a gold nanoparticle

The nonlinear optical properties of the CdSe/ZnS quantum dot quantum well (QDQW) in the vicinity of a spherical metal nano-particle (MNP) have been described. The third-order nonlinear optical susceptibility induced by the transition between E₁ (inside the well) and E₂ (outside the well) has been calculated for the third-harmonic generation (THG) under the effective mass approximation and modified by the local field theory. The parameters-dependent third-order nonlinear optical susceptibility for the THG has been specifically explored and the influence of the distance between the QDQW and the MNP on the third-order susceptibility for the THG in the system has been shown and analyzed.     

Polaron effects on the third-harmonic generations in a two-dimensional quantum pseudodot system

The third-harmonic generations (THG) considering polaron effects in the two-dimensional quantum pseudodot system with a uniform magnetic field are theoretically studied. It is found that the THG coefficient is strongly affected not only by an external magnetic field, but also by the geometrical size of the pseudodot system. Moreover, the theoretical values of the THG is obviously increased when considering the electron–LO–phonon interaction.     

Third-harmonic generation by cascading second-order nonlinear processes in a cerium-doped KTiOPO4 crystal

We have achieved effective third-harmonic generation (THG) by cascading second-harmonic and sum-frequency generation in a single cerium-doped KTiOPO (4) crystal by using femtosecond laser pulses at 1.32 microm. A conversion efficiency of 0.17% was achieved with an average pump power of 35 mW.Furthermore, a unique quadratic power dependence for this type of THG was confirmed. We developed a theory and obtained an analytical solution for the THG.The solution exactly describes the measured characteristics of the THG.     

Imaging of Ca(2)+ intracellular dynamics with a third-harmonic generation microscope

We describe the promising development of third-harmonic generation (THG) in laser scanning microscopy for study of the functional imaging of live biological cells. The dynamics of Ca(2+) in biological cells is shown. The Ca(2+) signal consists of a transient increase in the intracellular concentration. THG microscopy allows one to temporally visualize the release of Ca(2+) from internal stores and (or) calcium influx.     

Third-harmonic generation in a general two-component quasi-periodic optical superlattice

The quasi-periodic optical superlattice is a promising material for use in optical frequency conversion. We propose a method for designing a quasi-periodic structure for efficient third-harmonic generation (THG) at any given wavelength. With this method we have made a LiTaO(3) sample in which 27% THG at 0.48microm was achieved, together with a series of highly efficient multiwavelength second-harmonic generation outputs. The result is in good agreement with the theoretical prediction.     

The effective conversion bandwidth in single-doubler, dual-tripler broad-band third-harmonic generation

The physics processes in broad-band third-harmonic generation (THG) for the multicrystal cascade scheme have been studied in this paper. Assuring the THG efficiency is more than 60%, the effective conversion bandwidth is designed up to 2 nm for the single-doubler, dual-tripler, which is thrice as broad as that for the single-doubler, single-tripler.     

银纳米颗粒对胆固醇荧光的增强效用研究

在传统荧光光谱技术的基础上,结合金属纳米颗粒的增强荧光技术,探索提高荧光光谱技术检测人全血溶液中胆固醇含量的精度和分辨率的方法。实验研究方面,采用波长为407 nm的激光作为激发光,照射加入一定量银纳米颗粒作为荧光增强剂的人全血溶液,研究了银纳米颗粒对人全血溶液在可见光波段的荧光增强作用。结果表明,胶体状态的银纳米颗粒可以显著增强低浓度的人全血溶液荧光光谱的强度,且不同位置荧光发射峰的荧光增强效率随银胶加入量的增加均呈现先增后减的趋势,但不同峰位置的最强增强效率对应的银胶加入量不同。理论分析方面,根据实验结果及胆固醇分子和银纳米颗粒在溶液中的分布情况,建立了分子间距模型,并根据模型计算得出胆固醇分子和银纳米粒子之间的最佳增强荧光效果间距在12.19～25 nm范围内,这个结果和其他文献中的理论值吻合较好。综上所述,使用银纳米颗粒可实现全血溶液荧光的增强,研究结果为提高检测血液中多种物质的灵敏度和精度提供了有价值的参考作用。     

Non-linear phase-mismatch compensated by focusing for efficient THG in gases

A possibility of removing the limitation imposed by non-linear refraction on the attainable conversion efficiency is considered for third-harmonic generation (THG) in gaseous media. A numerical analysis has shown that by a proper focusing, the THG efficiency can approach values close to unity in spite of a substantially large value of the inhomogeneous non-linear refraction. The dependence of the conversion efficiency and the optimum linear phase-mismatch on the focusing tightness is presented for the steady-state and pulsed regimes.     

柱形量子点中的三阶极化率

利用量子力学的密度矩阵理论,在有效质量近似下，采用有限深势阱模型，导出了柱形量子点的三阶非线性极化率的解析表达式.通过数值计算，分析了GaAs/AlβGa1－βAs柱形量子点的三阶非线性极化率与量子点尺寸、掺杂浓度、入射光的频率和偏振方向等参量的关系.结果表明，三阶极化率峰值位置与这些参量密切相关，并且对于确定频率和偏振方向的入射光以及材料的掺杂浓度，存在与之相匹配的量子点尺寸，使三阶极化率达到极大，比体材料的相应值高出2个数量级以上.     

Efficient Ultraviolet Nanosources Based on Third-Harmonic Generation in Dielectric–Metal Composite Nanodisks

Dielectric materials with high indices have recently attracted much attention in the community of nanophotonics. Severe optical losses in visible–ultraviolet (UV) region, however, limit their applications. This article proposes dielectric–metal nanocomposites as alternative high-index materials for Mie-resonance-based applications. Such composite materials have high indices in the range of wavelength longer than plasmon resonance of inclusion metal nanoparticles, while they have much lower losses in the range from blue-violet down to near-UV compared with commonly used high-index materials such as silicon, enabling near-UV generation with high efficiency based on third-harmonic generation (THG). The numerical results show that ZnO nanodisk containing silver nanoparticles can generate near-UV radiation at 351.3 nm via THG with an efficiency about 20 times higher compared with silicon nanodisk under same pumping condition. Significantly high THG efficiency of 0.015% has been predicted with such a composite nanodisk supported by aluminum substrate under pumping with a peak intensity of 20 GW cm⁻², a spot size of 0.8 $\mu \mathrm{m}$, a duration of 50 fs at 1054 nm, respectively.     

Broadband Third-Harmonic Generation with a Composite KD*P Crystal

We predict that broadband efficient third-harmonic generation (THG) can be achieved with a frequency-doubling crystal and a novel composite KD*P tripler. The composite KD*P tripler is made of two partially deuterated KDP crystals with different deuteration levels by using the thermal bonding technique. The deuteration level of a partially deuterated KDP crystal is used as a degree of freedom to alter the phase-matching (PM) wavelength. Simulations show that the composite KD*P tripler can improve third-harmonic conversion efficiencies over a very wide band of input fundamental frequencies. In terms of robustness, alignment and stability, this THG scheme should be more promising than other broadband THG approaches because the composite KD*P tripler is a monolithic device.