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FDTD method can be used to compute the electromagnetic field scattered by the particles. FDTD method only provides the 6 vector electromagnetic field components ( Ex Ey Ez Hx Hy Hz) in discrete coordinates, and each component located on different physical point of the so called Yee cell. The values of the components are transient in time domain. For calculating the specific problem such as absorption cross section, scattering cross section and extinction cross section of the scatters, we usually integrates the time-averaged Poynting vector across a closed surface surrounding the scatters. The transient values of the field components derived from FDTD located at the Yee Cell grids must be translated into the values of the same physical point at the same physical time to get the time-averaged Poynting vectors. By this way we can get the highly accurate calculation results. The method of integrating the time-averaged Poynting vector over a certain closed surface is given in the paper. Comparing with the method of integrating the divergence of time-averaged Poynting vector over the volume region, our method of face integration is not only much more time saving for large size scatteres, from O(N 3 ) to O(N 2 ) in time complexity, and having a more direct physical meaning, but keeping the same calculating accurateness at the same time. We calculate the scattering efficiencies and the absorption efficiencies of the sphere of gold in 825 nm incident wave length, in size parameter ranging from 0.5 to 10 and from 0.1 to 1, respectively. The results of our calculation are compared with Mie theory, which are analytical results, to verify the correctness and the accurateness of our method. The spring models for simulating nano coil structures are studied by our method.

Using reactive radio-frequency magnetron sputtering technique, ZnO films are grown on Si (111) substrates with ZnO buffer layers deposited under different temperature with optimal condition of working pressure, sputtering power, flux of gas and sputtering time. In order to study the influence of ZnO buffer depositing temperature on the characteristic of the ZnO film, atomic force microscope, X ray diffraction, Raman spectroscopy and photoluminescence spectrum are used to analyze the morphology, growth orientation, Raman spectrum and optical properties of the ZnO films. It is concluded that the optimal depositing temperature of the ZnO buffer for the growth of the top ZnO film is 350 °C.

The optical properties of silver spherical nanoparticle dimer arrays with various incident wavelength are investigated by using the finite difference time domain method. Due to surface plasmon resonance, in the arrays of strongly coupled Ag nanoparticles, the energy of incident light is effectively confined in the gap of penultimate dimer under the influence of surface plasmonic reflection at the end of array structure. Furthermore, the suitable radius of the nanoparticles can be chosen to obtain the resonant peak at the optional position in the range of visible-nearinfrared wavelength. The above effects can be utilized to design effective functional end-structures in integrated optics.

It is a review about the industrialization of Nano-Optical Microscope (NOM, also referred to as the Near-field Optical Microscope). Two comparisons of AF/PSTM (Transmission Mode) with the first generation commercial A-SNOM and AF/RNOM(Reflective Mode) with A-RNOM have discussed. The commercially used A-SNOM can only obtain a transmissivity image of A-SNOM-T(x,y), but AF/PSTM can obtain the separating the transmissivity image PSTM-T(x,y) and the refractive index imge PSTM-n1(x,y). AF/RNOM can obtain the lower contrast reflective index image but ARNOM cannot. The reason how could Pohl have obtained the first A-SNOM image with a resolution of 20-25nm in 1984 but the commercial A-SNOM-T(x,y) only with the resolution in the 50~100nm range is also discussed. Conclusion on the proposal of AF/PSTM and combined AF/RNOM may be the best candidate for the second generation commercial use of NOM.

Metal nanostrip array for light transmission enhancement in the nanoslit is studied using a finite-difference time-domain method (FDTD). The strips with uniform shape are placed on upper side of a metal film with the nanoslit fabricated in it. It is found that the transmission efficiency can be promoted with an optimization of the strip. Effects of the single strip on the promotion are discussed in detail, a Fabry-Perot resonance model is competent for well understanding the phenomena.

The optical forces can be used to manipulate the particles whose dimensions ranging from some tens of nanometers to larger than a hundred nanometers. An electromagnetic wave exerting force on a metal particle at the wavelength far from the particle's plasmon resonance wavelength resembles trapping high refractive index dielectric particle. When designing the optical trapping experiments, we must consider the power of the incident light, the optical force produced by the incident light and the size of the particle being manipulated. The trapping of dielectric nanoparticles was studied with numeric simulation of Finite-Difference Time-Domain (FDTD) method. We use the total-field/scattered-field consistency boundary approach in FDTD method to simulate the focused incident beam interacting with the dielectric particles. The ten-cell-thick uniaxial perfectly matched layer (UPML) absorbing boundary condition is introduced to simulate the extension of the computation domain to infinity. The result field distributions in FDTD then are substituted into the Maxwell stress tensor to calculate the optical forces. The numeric simulation demonstrates the possibility of trapping dielectric particles transversely whose radii are comparable to wavelength.

Carbon nanocoils (CNCs) have attracted much attention due to their unique three-dimensional helix morphology, outstanding mechanical and electronic properties, and potential applications. Compared with carbon nanotubes, CNCs can be dispersed in solvents easily. In this paper, the manipulation of single CNCs by an optical tweezers has been demonstrated. It is found that these CNCs can be trapped, removed and rotated by the manipulation system, resulted from the asymmetrical distribution of optical trapping force generated on the CNCs with chiral features. Furthermore, the length of a single CNC can be adjusted by increasing the power of incident laser beam because the absorbed laser energy can be changed into thermal energy in a CNC. These results suggest that CNCs can be manipulated by an optical tweezers, which is suitable for the alignment of a CNC at a fixed position with a fixed length in electronic devices.

Optical properties of bowtie antennas are investigated using a numerical method of finite-difference time-domain (FDTD). The optical response in the antenna feed gap is simulated as functions of its geometry parameters (flare angle, arm length, apex width, thickness, gap dimension, as well as the index of substrate), which provide a clear guideline to exploit such antenna structures in practice.

According to the preparation of tapered fiber hemispherical micro-lens by hybrid etching and melting, a geometric calculation model for fabricating hemispherical micro-lens at the end of optical fiber by melting tapered flat fiber end into hemispherical fiber end has been developed. If the taper diameter and taper angle are obtainable, the radius of hemispherical micro-lens of the fiber taper after melting can be calculated. Particularly, hemi-spherical micro-lenses of optical fibers with various radii can be fabricated by etching-cleaving-melting method. According to the linear relationship between etching fiber diameter and etching time, as well as the characteristic of fiber volume maintaining constant before and after electric arc melting, the relationship between the radius of fiber hemispherical micro-lens and etching time was deduced in this paper. Through controlling the etching time precisely after calculating the etching rate, which is determined by the sampling and analysis of the etched fiber, the hemi-spherical micro-lenses with different radius at the fiber ends can be produced. The experiments were conduct to test the operability of this method. The results showed that radii of micro-lenses fabricated by the etching-cleaving-melting method made a good coincidence with the designed radius values of 10µm and 20µm.

Ultrahigh density near-field optical storage is pre-investigated in this paper. 1. The design of super- lens and simulation is investigated. 2. The GaAs pyramid micro-tips were grown by the method of selecting Liquid Phase Epitaxy. 3. The storage film of Ge2Sb2Te5 is grown by the magnetron sputtering method on the Si (100) substrates. 4. Several characteristics of the storage film have been measured and analysed.© (2007) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

In this report, based on the near-field Raman theory which mechanism is fundamental different with the far-field Raman, a new viewpoint of near-field Raman was brought out. In this view, to be the excitation light, the effect of evanescent light in near-field Raman was emphasized, at same time, the evanescent light component in the Raman scattering light was noticed, too. The sample could be excited through evanescent light and the component of evanescent light in Raman scattering light was collected entirely in the novel ultra-sensitive near-field Raman sample cell. According to the sample cell, initial experiment was performed. The high aperture oil immersed object lens was employed to form excitation light which included evanescent light component. High signal-to-noise surface enhanced Raman scattering (SERS) signal of rat serum was obtained. By analysing the Raman spectrum, it was found that the new Raman peaks come out because of the excitation light including evanescent light.

We have developed an Atomic Force / Photon Scanning Tunneling Microscope (AF/PSTM) to eliminate the optical false image caused by topography of sample in PSTM. The key element of this system is bi-functional bent optical fiber probe, which can both be an optical cantilever and a device to collect the evanescent wave in near field of samples. In this paper, we derived a method to fabricate the bi-functional bent optical probes of AF/PSTM using communication optical fibers. The heated pulling combined with chemical etching method is proposed and developed. Fiber probes with an apex having a diameter smaller than 100nm could be produced with a controlled cone angles vary from 40 to 90 degrees. The back of the probe is finally coated with aluminum to enhance the reflection and with SiO 2 to prevent Al film from oxidating in the atmosphere. This method is straightforward and fast. Using probes made with this method, the images of biology samples are obtained and the image separation is realized.

With the fast development of scanning probe microscope, especially atomic force microscope (AFM), an imaging tool for life sciences researches is provided. Biological species imaging is one of the fundamental studies in life sciences, so it becomes one of the most important applications of AFM imaging. In this paper, AFM images of proteus species separately by contact-mode and intermittent-contact MacMode are obtained and investigated, and also are compared with its image of scanning electron microscope (SEM). Note that flagella are presented in SEM image while no evidence of flagella is observed when proteus species were imaged in AFM. This difference may be having something to do with sample preparation. The other possibility of this difference is that the proteus species which imaged was immature. Moreover, the images by MacMode in liquid medium show the outer surface of proteus species is smooth while the images by contact-mode in air show folding of the surface. The latter has clearly greater resolution than the former.

Photon Scanning Tunneling Microscope (PSTM) is a near-field optical microscope that can measure local optical properties with high resolution beyond the diffraction limit and was widely applied in practices in recent years. The resolution of PSTM, which mainly depends on the shape of the taper tip, is an important issue to be discussed in the application. In this paper, the near-field distribution around a new PSTM probe is simulated by the method of 3-D Finite-Difference Time-Domain (FDTD). In this model, a nanometric metallic pyramid is attached at the apex of the metal-coated probe. Considering the interaction between the sample and the probe tip, the near-field distribution in a section at certain height is plotted as a function of the various sample positions. In order to optimize the optical property of this kind of optic fiber probe tip, the influence of the parameters of the taper tip can also be studied. To understand the effect of the probe film and the metal tip, the electromagnetic field distribution in the vicinities of the sample and the fiber probe during the third period is plotted. Thus, these simulated results offer references for the selection of the probe shape in experiments.

According to author's Chinese invented patent ZL96 I II 979.9 named "The method of separating image of AF/PSTM (atom force and photon scanning tunneling microscope)", the first system ofAF/PSTM has been developed. Its principle, photograph, block diagram and some images ofan examination sample have been given in this paper. There are three advantages of this system: (1) AF/PSTM can eliminate the optical false image which caused by topography of sample in PSTM; (2) The optical images and topographic image of sample are separated with this AF/PSTM; (3) From once scanning imaging two optical images (refractive index image and transmissivity image) and two AFM images (topography image and phase or grads oftopography image) can be obtained.

It is important to analyze the images obtained by photon scanning tunneling microscope (PSTM). Recently some theories have been developed including finite-difference time-domain (FDTD) method applied in near field optics. In this article wc extend a simple FDTD method (equivalent incident wave method) to PSTM system, which has been widely used to detect objects buried underground in geophysics. In PSTM system lighting wave is evanescent wave, that is the equivalent incident wave exciting the samples and probe over the interface. Numerical simulations show that the results ofthis method are in agreement with the results ofthe moment method and perturbation theory.

Our research group has recently developed a new type scanning probe microscope —AF/ PSTM. Using this setup, the optical false image caused by the inclination of sample surface can be eliminated; the optical image and the topography image are separated; and also two optical images (refractive index image, transmittivity image) and two AFM images (topography image, phase image) are obtained during one scanning. As a primary biologic application, this setup is engaged in the imaging of some biologic samples. The primary images ofthese biologic samples are obtained. Due to the advantage of AFIPSTM, four images can be acquired at the same time during one scanning. Consequently more information ofsample is given by comparing these images. This work shows that the AF/PSTM may be improved to be a useful tool in biology research.

Photon Scanning Tunneling Microscope (PSTM) is a newly developed technique. As a near-field optical microscope, it has the high resolution breaking through the diffraction limit and the advantage for easy to prepare the samples. PSTM is a useful tool in the inspection for many kinds of material film as the image containing the sample's information of topography and refractive index. We have developed a PSTM with resolution 5 to approximately 10 nm and scanning range 6 X 6 micrometer. By making use of two lasers, the false image caused by inclination of sample surface can be reduced. This PSTM is engaged in the inspection of Al 2 O 3 optical waveguide film made using ion-beam-enhanced-deposition (IBED) technique at different substrate temperature. The PSTM images of the optical waveguide film are obtained and analyzed. The PSTM images show that as the increasing of the substrate temperature during the deposition, the sample images of refractive index and topography tend to smooth and even, consequently the scattering loss can be decreased. The conclusion is that by properly increasing the temperature of the substrate during the deposition period, the scattering loss can be decreased and the property of Al 2 O 3 optical waveguide can be improved.

A comparison between PSTM and A-SNOM in resolution, contrast and optical efficiency is discussed. The order of magnitude roughly estimated shows that PSTM is must better than commercial A-SNOM.

This paper attempts to answer the question of 'how to explain the image of photon scanning tunneling microscope (PSTM)'. To explain the image of PSTM, the essential difficulty is the false image information within the complex image of the topographical image and refractive index image of sample. In this paper, we have derived the PSTM imaging formula and introduced the eliminating false image information method and image separating method, and discussed the key to super-resolution of near-field optical microscopy. Numerical simulation and experiments with the method of perturbation diffraction combined with (pi) - symmetric lighting eliminating false image information are provided.

In this paper, the three-wave interactions in a nonlinear dissipation medium are researched and three conclusions obtained. (1) The three-wave interactions may give bifurcation and have chaotic solutions. Chaotic criteria are given for less dissipation of pump wave. (2) The stable and analytical asymptotical solution is obtained for more dissipation of pump wave. (3) The stable asymptotical solution and the criteria of Hopff bifurcation are obtained and the Hopff bifurcation may make the transfer of momentum and energy.© (1992) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.