2009, 7(10) Column
Chinese Optics Letters 第7卷 第10期
We fabricate photonic crystal slab microcavities embedded with GaAs quantum dots by electron beam lithography and droplet epitaxy. The Purcell effect of exciton emission of the quantum dots is confirmed by the micro photoluminescence measurement. The resonance wavelengths, widths, and polarization are consistent with numerical simulation results.
光子晶体 量子点 GaAs Purcell效应 050.5298 Photonic crystals 230.5590 Quantum-well, -wire and -dot devices 300.2140 Emission A three-dimensional model of GaAs/AlGaAs quantum double rings in the lateral static electric field is investigated theoretically. The eigenvalue problem with the effective-mass approximation is solved by means of the finite-element method. The energy levels and wave functions of quantum-confined electrons and heavy holes are obtained and show an agreement with our previous theoretical and experimental studies. It is shown in the approximation of neglecting the Coulomb attraction between the electron and heavy hole that a relatively large Stark shift of exciton emission of 4 meV is attainable with an applied electric field of 0.7 kV/cm.
量子双环 GaAs Stark位移 有限元法 250.5590 Quantum-well, -wire and -dot devices 160.6000 Semiconductor materials 260.6580 Stark effect Tunneling-induced \pi-phase shift with a single-photon signal field in asymmetric double quantum wellsDownload:568次
A theoretical investigation is carried out into the cross phase modulation (XPM) in an asymmetric double AlGaAs/GaAs quantum wells structure with a common continuum. It is found that, combining resonant tunneling-induced transparency and constructive interference in the third-order Kerr effect, a giant XPM can be achieved with vanishing linear and nonlinear absorptions, accompanied by the velocities of the probe and signal fields being matched. Furthermore, this giant XPM could induce a \pi-phase shift at a single-photon level which is favorable for the applications in two-qubit quantum logic gates.
双量子阱结构 相位匹配 交叉相位调制 共振隧穿诱导透明 190.3270 Kerr effect 190.4400 Nonlinear optics, materials 270.1670 Coherent optical effects 270.5585 Quantum information and processing A novel atomic force microscope operating in liquid with open probe unit and optimized laser tracking systemDownload:632次
A novel atomic force microscope (AFM) for large samples to be measured in liquid is developed. An innovative laser beam tracking system is proposed to eliminate the tracking and feedback errors. The open probe design of the AFM makes the operation in liquid convenient and easy. A standard 1200-lines/mm grating and a sheet of filter paper are imaged respectively in air and liquid to confirm its performance. The corrosion behavior of aluminum surface in 1-mol/L NaOH solution is further investigated by the AFM. Experimental results show that the system can realize wide range (20 × 20 (\mu m)) scanning for large samples both in air and liquid, while keeping nanometer order resolution in liquid by eliminating the tracking and feedback error.
原子力显微镜 液相操作 光路追踪 跟踪误差 反馈误差 110.0180 Microscopy 180.0180 Microscopy 180.5810 Scanning microscopy Optical methods and MTT method are used to characterize the antiproliferation effect of antitumor drug 9-aminoacridine (9AA) with and without silver nanoparticles. Intracellular surface enhanced Raman scattering (SERS) spectra and fluorescent spectra of 9AA indicate the form of 9AA adsorbed on the surface of silver nanoparticles. Although both silver nanoparticles and antitumor drug can inhibit the growth of Hela cells, silver nanoparticles can slow down the antiproliferation effect on Hela cells at low concentration of antitumor drugs. Our experimental results suggest that silver nanoparticles may serve as slow-release drug carriers, which is important in antitumor drug delivery.
银纳米 表面增强拉曼散射 药物 160.4236 Nanomaterials 290.5860 Scattering, Raman 180.1790 Confocal microscopy The irradiation of cells combined with the immunoconjugate of gold nanoparticles by the short pulse laser can make the plasma membrane be transiently permeabilized, which can be used to transfer exogenous molecules into the cells. We explore this technique as a novel gene transfection method for floating cells. Three different floating cells exposed to the laser are selectively transfected with fluorescein isothiocyanatedextran, antibody, and green fluorescent protein (GFP) coding plasmids, and the viability of cells are determined by propidium iodide. For fluorescein isothiocyanate-dextran, the best transfection efficiency of 65% is obtained; for the antibody, it is 74%; whereas for the green fluorescent protein coding plasmids, a very small transfection efficiency is gained. If the transfection efficiency is improved, gold nanoparticles will be very useful as mediator for gene transfection in living cells.
纳米金颗粒 细胞膜通透性 激光转染 170.2520 Fluorescence microscopy 140.3440 Laser-induced breakdown 350.5340 Photothermal effects We report the high speed scanning submicronic microscopy (SSM) using a low cost polymer microlens integrated at the extremity of an optical fiber. These microlenses are fabricated by a free-radical photopolymerization method. Using a polymer microlens with a radius of curvature of 250 nm, a sub-micrometric gold pattern is imaged experimentally by SSM. Different distances between the tip and the sample are used with a high scanning speed of 200 cm/s. In particular, metallic absorption contrasts are described with an optical spatial resolution of 250 nm at the wavelength of 532 nm. Moreover, finite-difference time-domain (FDTD) simulations concerning the focal lengths of microlenses with different geometries and heights support the experimental data.
微透镜 聚合物 显微镜 130.0130 Integrated optics 160.0160 Materials 180.0180 Microscopy Cutoff characteristics of dielectric-f illed circular holes embedded in dispersive plasmonic mediumDownload:510次
The cutoff characteristics of dielectric-filled circular holes embedded in a dispersive plasmonic medium are investigated. Since two distinctive operating modes, surface plasmon polariton and circular waveguide modes, can exist in the slow and fast wave regions, respectively, the cutoff characteristics for each are separately investigated for linear and radial polarizations of the guided fields. As a result, the cutoff wavelengths for the linear and radial polarizations with very small subwavelength hole radii are found to be limited by the plasma resonance wavelength and plasma wavelength, which in turn are dependent and independent, respectively, of the dielectric constant of the dielectric filler material.
截止波长 亚波长圆孔 导波色散 表面等离子体极化子 圆形波 230.7370 Waveguides 250.5403 Plasmonics 240.6680 Surface plasmons 130.2790 Guided waves Improving the sensitivity of fiber-optic SPR sensor via radially polarized beam excitationDownload:1399次
We study the sensing properties of an intensity-modulated fiber-optic surface plasmon resonance (SPR) sensor using radially polarized beam (RPB). Because of the rotational symmetry of fiber and RPB, surface plasmon can be excited more efficiently at the sensor surface, which results in an obvious improvement of the sensitivity. Our experiments demonstrate that the sensitivity in the case of RPB illumination is three times higher than that of linearly polarized beam illumination.
光纤传感 表面等离子体共振 轴向偏振光 060.2370 Fiber optics sensors 240.6680 Surface plasmons 310.5448 Polarization, other optical properties Modified solution-processible fabrication of metallic photonic crystals with template removalDownload:579次
High-temperature annealing and pre-annealing lift-off procedures are employed to improve the solution processible technique for the fabrication of one- (1D) and two-dimensional (2D) metallic photonic crystals (MPCs) based on colloidal gold nanoparticles. This enables the successful fabrication of gold nanowires or nanocylinder array structures with the photoresist template removed completely, which is crucial for the application of MPCs in biosensors and optoelectronic devices. Microscopic measurements show homogeneous 1D and 2D photonic structures with an area as large as 100 mm2. Plasmonic resonance of the gold nanostructures and its coupling with the resonance mode of the planar waveguide underneath the photonic structures are observed, implying the excellent optical properties of this kind of MPCs based on the improved fabrication technique.
金纳米颗粒胶体 波导耦合金属光子晶体 溶液法制备技术 粒子等离子共振 角分辨稳态光谱学 050.6624 Subwavelength structures 160.4236 Nanomaterials 160.5298 Photonic crystals 240.6680 Surface plasmons Cu2O particles cube with ordered pores are electrodeposited by using colloidal crystal template method. The shape of Cu2O cube particle is partly determined by its growing habit. Therefore, Cu2O cube particles with ordered pores are fabricated instead of three dimensional inverse opal structures.
金纳米颗粒胶体 波导耦合金属光子晶体 溶液法制备技术 粒子等离子共振 角分辨稳态光谱学 160.4670 Optical materials 160.4760 Optical properties 160.5293 Photonic bandgap materials Ultraviolet photo-lithography is employed to introduce two-dimensional (2D) photonic crystal (PC) structure on the top surface of GaN-based light emitting diode (LED). PC patterns are transferred to 460-nm-thick transparent indium tin oxide (ITO) electrode by inductively coupled plasma (ICP) etching. Light intensity of PC-LED can be enhanced by 38% comparing with the one without PC structure. Rigorous coupled wave analysis method is performed to calculate the light transmission spectrum of PC slab. Simulation results indicate that total internal reflect angle which modulated by PC structure has been increased by 7°, which means that the light extraction efficiency is enhanced outstandingly.
光子晶体 发光二极管 全内反射角。 230.5298 Photonic crystals 230.3670 Light-emitting diodes 230.4000 Microstructure fabrication Six high-index cores are embedded around the central solid core of the photonic crystal fiber to form a fiber embedded photonic crystal fiber (FEPCF), which is investigated based on the beam propagation method. In this structure, the Gaussian mode could be transferred to the ring mode. So FEPCF could used as a mode convertor.
光子晶体光纤 模式转换 光纤嵌入式技术 光束传播 060.2280 Fiber design and fabrication 060.2340 Fiber optics components 060.5295 Photonic crystal fibers 230.3990 Micro-optical devices A high-permittivity (high-k) material is applied as the gate dielectric layer in a silicon metal-oxide-semiconductor (MOS) capacitor to form a special electro-optic (EO) modulator. Both induced charge density and modulation efficiency in the proposed modulator are improved due to the special structure design and the application of the high-k material. The device has an ultra-compact dimension of 691 \mu m in length.
硅基调制器 电光调制器 高K栅层 MOS电容 230.4110 Modulators 250.4110 Modulators 250.6715 Switching 230.2090 Electro-optical devices The spontaneous emission rate of two interacting excited atoms near a dielectric interface is studied using the photon closed-orbit theory and the dipole image method. The total emission rate of one atom during the emission process is calculated as a function of the distance between the atom and the interface. The results suggest that the spontaneous emission rate depends not only on the atomic-interface distances, but also on the orientation of the two atomic dipoles and the initial distance between the two atoms. The oscillation in the spontaneous emission rate is caused by the interference between the outgoing electromagnetic wave emitted from one atom and other waves arriving at this atom after traveling along various classical orbits. Each peak in the Fourier transformed spontaneous emission rate corresponds with one action of photon classical orbit.
自发辐射率 偶极矩 闭合轨道 干涉 020.0020 Atomic and molecular physics 020.4900 Oscillator strengths 070.2590 ABCD transforms 270.5580 Quantum electrodynamics Infrared dim target detection based on fractal dimension and third-order characterizationDownload:510次
We propose an improved algorithm based on fractal dimension and third-order characterization to detect dim target with cluttered background in an infrared (IR) image. We also illustrate the performance and efficiency comparisons between the presented algorithm and the traditional fractal detection method on real IR images. The experimental results show that the proposed algorithm is robust and efficient for IR dim target detection.
弱小目标检测 红外图像 分维 三阶特征量 040.1880 Detection 040.3060 Infrared 100.2000 Digital image processing 100.3008 Image recognition, algorithms and filters As one of the next generation imaging spectrometers, interferential spectrometer has been paid much attention. With traditional spectrum compression methods, the hyperspectral images generated by interferential spectrometer can only be protected with better visual quality in spatial domain, but its optical applications in Fourier domain are often ignored. So the relation between the distortion in Fourier domain and the compression in spatial domain is analyzed in this letter. Based on this analysis, a novel coding scheme is proposed, which can compress data in spatial domain while reducing the distortion in Fourier domain. The bitstream of set partitioning in hierarchical trees (SPIHT) is truncated by adaptively lifting the rate-distortion slopes of zerotrees according to the priorities of optical path difference (OPD) based on rate-distortion optimization theory. Experimental results show that the proposed scheme can achieve better performance in Fourier domain while maintaining the image quality in spatial domain.
高光谱图像压缩 干涉高光谱 SPIHT 100.4145 Motion, hyperspectral image processing 100.2960 Image analysis 070.4790 Spectrum analysis We study the high numerical aperture focusing properties and typical applications of axially-symmetric polarized beams (ASPBs) with high polarization orders. We calculate the field distribution near focus of an aplanatic system for incident ASPBs with different polarization orders and initial azimuthal angles, and based on the simulation results, we find some unique focusing properties of the beams, such as ever on-axis energy null, strong longitudinal field, and flowerlike intensity distribution at focus. In addition, we can manipulate the three-dimensional (3D) focused field distribution flexibly by use of diffractive optical elements (DOEs), which will give rise to some interesting applications, and we also discuss possible applications and present an example of a 3D optical chain at last.
偏振 成像理论 激光光束整形 110.2990 Image formation theory 260.5430 Polarization 140.3300 Laser beam shaping Swept source optical coherence tomography based on non-uniform discrete fourier transformDownload:1323次
A high-speed high-sensitivity swept source optical coherence tomography (SSOCT) system using a high speed swept laser source is developed. Non-uniform discrete fourier transform (NDFT) method is introduced in the SSOCT system for data processing. Frequency calibration method based on a Mach-Zender interferometer (MZI) and conventional data interpolation method is also adopted in the system for comparison. Optical coherence tomography (OCT) images from SSOCT based on the NDFT method, the MZI method, and the interpolation method are illustrated. The axial resolution of the SSOCT based on the NDFT method is comparable to that of the SSOCT system using MZI calibration method and conventional data interpolation method. The SSOCT system based on the NDFT method can achieve higher signal intensity than that of the system based on the MZI calibration method and conventional data interpolation method because of the better utilization of the power of source.
光学相干层析 非均匀傅立叶变换 扫频光源 110.4500 Optical coherence tomography 140.3600 Lasers, tunable Synchronization of chaotic vertical-cavity surface-emitting lasers (VCSELs) is achieved by external chaotic signal modulation successfully. Simulation indicates that we can get chaos synchronization if the intensity of external chaotic signal is large enough. First of all, we use direct current modulation to achieve the chaos of VCSELs, and determine the laser’s chaotic state by analyzing time series of the output and the corresponding power spectrum. And then we achieve synchronization of the two chaotic systems by external chaotic signal parameter modulation. We also find that the larger the modulation intensity is, the easier it is to achieve synchronization for chaotic VCSELs. This approach can also be applied to systems with a number of modulated lasers.
非线性光学 混沌 混沌同步 参数调制 垂直强面发射半导体激光器 190.0190 Nonlinear optics 190.3100 Instabilities and chaos 140.7260 Vertical cavity surface emitting lasers Thermal-induced nonlinear optical characteristics of ethanol solution doped with silver nanoparticlesDownload:1069次
The investigation of nonlinear optical characteristics of ethanol solution doped with silver nanoparticles is presented. A large thermal-induced third-order nonlinear refractive index up to –1.941×10?7 cm2/W is obtained from the mixed solution under 488-nm continue wave (CW) laser irradiation, which may result from surface plasmon resonance (SPR) enhancement effect of silver nanoparticles as well as high thermo-optic coefficient and low thermal conductivity of ethanol. Obvious spatial self-phase modulation and influence of thermal-induced negative lens effect are observed when a beam propagates through this solution, indicating promising applications such as optical limiting, beam flattening, and so on.
非线性光学 表面等离子体共振 纳米银颗粒 z-scan扫描技术 190.0190 Nonlinear optics 160.4330 Nonlinear optical materials 160.4236 Nanomaterials 240.6680 Surface plasmons A ZnO thin film covered by TiO2 nanoparticles is prepared by electron beam evaporation. The structure and surface morphology of the sample are analyzed by X-ray diffraction (XRD) and atomic force microscopy (AFM), respectively. Photoluminescence is used to investigate the fluorescent property of the ample. The results show that the ultraviolet (UV) emission of the ZnO thin film is greatly enhanced after it is covered by TiO2 nanoparticles while the green emission is suppressed. The enhanced UV emission mainly results from the fluorescence resonance energy transfer (FRET) between ZnO thin film and TiO2 nanoparticles. This TiO2-ZnO composite thin film can be used to fabricate high-efficiency UV emitters.
ZnO薄膜 TiO2纳米颗粒 光致发光 荧光共振能量转移 240.6675 Surface photoemission and photoelectron spectroscopy 250.5230 Photoluminescence 260.5740 Resonance Nano-TiO2 thin films are deposited by radio frequency (RF) magnetron sputtering using TiO2 ceramic target and characterized by X-ray diffractometer, atomic force microscope, and ultraviolet-visible spectrophotometer. The photocatalytic activity is evaluated by light-induced degradation of methyl orange solutions (5, 10, and 20 ppm) using a high pressure mercury lamp as the light source. The film is amorphous, and its energy gap is 3.02 eV. The photocatalytic degradation of methyl orange solution is the first-order reaction and the apparent reaction rate constants are 0.00369, 0.0024, and 0.00151 for the methyl orange solution concentrations of 5, 10, and 20 ppm, respectively.
二氧化钛薄膜 射频磁控溅射 光催化 甲基橙 能隙 240.6670 Surface photochemistry 310.6860 Thin films, optical properties A new dynamic model is developed for simulating the widely tunable grating assisted codirectional coupler with rear sampled grating reflector (GCSR) lasers. The gain section of the device is calculated in timedomain using traveling-wave method, while the transmission spectrum of the coupler and the reflection spectrum of the reflector are firstly simulated in frequency-domain, and then transformed into time-domain via digital filter approach. Both static and dynamic performances based on this model agree well with the published results. Compared with previous works, this new model is more efficient and applicable, especially in the dynamic simulation.
GCSR半导体激光器 行波法 传输矩阵法 数字滤波器法 250.3140 Integrated optoelectronic circuits 250.5300 Photonic integrated circuits 250.5960 Semiconductor lasers An investigation is made on the optical nonlinear characteristics of MgF2 films containing Cu nanoparticles. When the Cu volume fraction is 0.1, at approximately \varepsilonm+ 2\varepsilond= 0, the film exhibits a strong third-order optical nonlinear refractive coefficient of 1.0×10-9 cm2/W, a nonlinear refractive index of about ?4.0×10-7 esu, a third-order optical nonlinear response of about 6.8×10-8 esu, and a figure of merit of about 1.0×10-11. The result shows that the film may have potential applications in optoelectronic technology.
Cu-MgF2复合颗粒薄膜 微结构 光学非线性特性 310.0310 Thin films 310.6628 Subwavelength structures,nanostructures 310.6860 Thin films, optical properties Tantalum pentoxide thin films are prepared by oblique angle electron beam evaporation. The influence of flux angle on the surface morphology and microstructure is investigated by scanning electron microscopy (SEM). The Ta2O5 thin films are anisotropic with highly orientated nanostructure of slanted columns. The porous microstructure of the as-deposited films results in the decrease of effective refractive index and packing density with increasing deposition angle. The anisotropic structure results in optical birefringence. The in-plane birefringence increases with the increase of deposition angle and reaches the maximum of 0.055 at the deposition angle of 70°. Anisotropic microstructure and critical packing density are the two key factors to influence the in-plane birefringence.
倾角沉积 Ta2O5薄膜 双折射 310.0310 Thin films 240.0240 Optics at surfaces 动态信息
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