排序方式: 共有127条查询结果,搜索用时 93 毫秒
91.
F. Formanek Y. De Wilde L. Aigouy W. K. Kwok L. Paulius Y. Chen 《Superlattices and Microstructures》2004,35(3-6):315
We have used a home-made apertureless near-field scanning optical microscope (ANSOM) for mapping nanometric steps between SiC and gold regions under visible (λ=655 nm) and infrared (λ=10.6 μm) illumination. The images, obtained with a signal demodulation at the tip oscillation frequency and at higher harmonics, clearly show optical contrasts with a subwavelength resolution of about 30 nm. Other images recorded in the visible on a YBa2Cu3O7 crystal indicate that the tip used in our experiments is able to reveal polarization effects. We also present a near-field thermal optical microscope (NTOM) which operates without any external illumination. In this new kind of microscope, the laser source which is usually used to excite the evanescent waves, is replaced by a simple heating of the sample. The electromagnetic radiation locally scattered by the tip comes from the thermal radiation. Our results with this new technique prove a 200 nm lateral resolution. 相似文献
92.
By the acoustic holography method, it was found that there were multiple nearby noise sources, which are hard to be rejected by using the conventional beamforming technique. Instead of the conventional beamforming, we propose a new adaptive beamforming method to suppress nearby generated flow noise by using sonar sub-arrays. 相似文献
93.
S.J. Chua S. Tripathy P. Chen E. Takasuka M. Ueno 《Physica E: Low-dimensional Systems and Nanostructures》2005,25(4):356-365
Using near-field scanning optical microscopy (NSOM), we report the spatial distribution of photoluminescence (PL) intensity in III-nitride-based semiconductor layers grown on GaN substrates. Undoped GaN, In0.11Ga0.89N, and In0.13Ga0.87N/GaN multi-quantum wells (MQWs) were grown by metal organic chemical vapor deposition (MOCVD) on freestanding GaN substrates. Micro-Raman spectroscopy has been used to evaluate the crystalline properties of the GaN homoepitaxial layers. The variation of the PL intensity from the NSOM imaging indicates that the external PL efficiency fluctuates from 20% to 40% in the 200 nm InGaN single layer on freestanding GaN, whereas it fluctuates from 20% to 60% in InGaN/GaN MQWs. In the NSOM-PL images, bright island-like features are observed. After deconvolution with the spatial resolution of the NSOM, the size of these features is estimated to be in the range of 150–250 nm. 相似文献
94.
95.
Gang Bao Peijun Li 《计算数学(英文版)》2007,25(3):252-265
A regularized recursive linearization method is developed for a two-dimensional in-verse medium scattering problem that arises in near-field optics, which reconstructs the scatterer of an inhomogeneous medium deposited on a homogeneous substrate from data accessible through photon scanning tunneling microscopy experiments. In addition to the ill-posedness of the inverse scattering problems, two difficulties arise from the layered back-ground medium and limited aperture data. Based on multiple frequency scattering data, the method starts from the Born approximation corresponding to the weak scattering at a low frequency, each update is obtained via recursive linearization with respect to the wavenumber by solving one forward problem and one adjoint problem of the Helmholtz equation. Numerical experiments are included to illustrate the feasibility of the proposed method. 相似文献
96.
We report on the novel design of the near-field scanning optical microscope (NSOM) which operates in liquid environment. A resonance tracking digital scanning method is applied to compensate the resonance shift due to the evaporation of the liquid in the atmospheric pressure. By this method, stable operation of NSOM system is demonstrated by showing topographic images of the metallic grating embedded in liquid environment. 相似文献
97.
Takahiko Ishii Yosuke Mizuno Daisuke Koyama Kentaro Nakamura Kana Harada Yukiyoshi Uchida 《Ultrasonics》2014
We developed a plate-shaped non-contact transporter based on ultrasonic vibration, exploiting a phenomenon that a plate can be statically levitated at the place where its gravity and the acoustic radiation force are balanced. In the experiment, four piezoelectric zirconate titanate elements were attached to aluminum plates, on which lattice flexural vibration was excited at 22.3 kHz. The vibrating plates were connected to a loading plate via flexible posts that can minimize the influence of the flexure induced by heavy loads. The distribution of the vibration displacement on the plate was predicted through finite-element analysis to find the appropriate positions of the posts. The maximum levitation height of this transporter was 256 μm with no load. When two vibrating plates were connected to a loading plate, the maximum transportable load was 4.0 kgf. 相似文献
98.
A. Hartschuh H. Qian C. Georgi M. Böhmler L. Novotny 《Analytical and bioanalytical chemistry》2009,394(7):1787-1795
We review recent experimental studies on single-walled carbon nanotubes on substrates using tip-enhanced near-field optical
microscopy (TENOM). High-resolution optical and topographic imaging with sub 15 nm spatial resolution is shown to provide
novel insights into the spectroscopic properties of these nanoscale materials. In the case of semiconducting nanotubes, the
simultaneous observation of Raman scattering and photoluminescence (PL) is possible, enabling a direct correlation between
vibrational and electronic properties on the nanoscale. So far, applications of TENOM have focused on the spectroscopy of
localized phonon modes, local band energy renormalizations induced by charge carrier doping, the environmental sensitivity
of nanotube PL, and inter-nanotube energy transfer. At the end of this review we discuss the remaining limitations and challenges
in this field.
Figure Tip-enhanced Raman scattering and photoluminescence spectroscopy with sub 15 nm spatial resolution provides novel insights
into the electronic and vibronic properties of single-walled carbon nanotubes. 相似文献
99.
The ALMA band 9 (600–720 GHz) receiver is a dual channel heterodyne system which is capable of detecting orthogonally polarised signals utilising a wire grid beam splitter. Two Superconductor–Insulator–Superconductor (SIS) mixers mounted behind hybrid mode corrugated horns are coupled to the 12 m Cassegrain antenna via a wavelength independent configuration of two off-axis elliptical mirrors.We outline an approach involving accurate physical optics simulations in conjunction with precise experimental measurements of the complete optical front-end which guarantees the highest performances. This practical verification approach can be generalised to all quasi-optical receivers to validate system performance. In this paper, we verify the optical design and estimate antenna system efficiency. Comparison between measurement and simulation indicates precise information is achievable in estimating system performance allowing potential improvements in ALMA instrument calibration accuracy. 相似文献
100.
Theoretical study of optical recording with a solid immersion lens illuminated by focused double-ring-shaped radially-polarized beam 总被引:1,自引:0,他引:1
Based on the Richards–Wolf vector diffraction theory, the intensity distributions in the recording sample near a solid immersion lens are calculated for two different radially-polarized beams ( and modes). Numerical results show that a double-ring-shaped mode focusing has some excellent features in near-field optical storage, compared with a single-ring-shaped mode focusing. The recording density is markedly improved, the focal depth of the near-field recording system is substantially increased, and a subsurface recording is effectively obtained using the mode focusing. 相似文献