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941.
S. T. Dawkins R. Chicireanu M. Petersen J. Millo D. V. Magalh?es C. Mandache Y. Le?Coq S. Bize 《Applied physics. B, Lasers and optics》2010,99(1-2):41-46
We have developed an ultra-stable source in the deep ultraviolet, suitable to fulfil the interrogation requirements of a future fully-operational lattice clock based on neutral mercury. At the core of the system is a Fabry–Pérot cavity which is highly impervious to temperature and vibrational perturbations. The mirror substrate is made of fused silica in order to exploit the comparatively low thermal noise limits associated with this material. By stabilizing the frequency of a 1062.6 nm Yb-doped fiber laser to the cavity, and including an additional link to LNE-SYRTE’s fountain primary frequency standards via an optical frequency comb, we produce a signal which is both stable at the 10?15 level in fractional terms and referenced to primary frequency standards. The signal is subsequently amplified and frequency-doubled twice to produce several milliwatts of interrogation signal at 265.6 nm in the deep ultraviolet. 相似文献
942.
We present a mathematical model and its numerical implementation for the analysis of the interaction of spatially partially coherent electromagnetic fields with micro- and nanostructured objects. The model is based on the decomposition of the incident field into a set of fully coherent but mutually uncorrelated elementary field modes, and the use of the Fourier Modal Method (FMM) with the S-matrix propagation algorithm. We apply the model to studies of the excitation of surface plasmons in thin metallic slabs, nanowires, and resonant structures. We demonstrate, e.g., that the plasmon excitation efficiency is not essentially affected by the degree of spatial coherence. However, certain plasmon interference effects can be efficiently smoothed out by using illumination with reduced coherence. 相似文献
943.
Making use of exact and quasistatic expressions for the field in near-field imaging of a point dipole by a thin silver slab, we calculate the point-spread function and the associated image resolution. We show that the resolution, which depends on the silver slab thickness and the dipole orientation, generally is better than the conventional diffraction limit and can be as high as λ/8. The results substantially agree with recent theoretical and experimental studies on 2D objects. 相似文献
944.
Lana G. Kaiser Ma?gorzata Marjańska Gerald B. Matson Isabelle Iltis Seth D. Bush Brian J. Soher Susanne Mueller Karl Young 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2010,202(2):259-266
Glutathione (GSH) is a powerful antioxidant found inside different kinds of cells, including those of the central nervous system. Detection of GSH in the human brain using 1H MR spectroscopy is hindered by low concentration and spectral overlap with other metabolites. Previous MRS methods focused mainly on the detection of the cysteine residue (GSH-Cys) via editing schemes. This study focuses on the detection of the glycine residue (GSH-Gly), which is overlapped by glutamate and glutamine (Glx) under physiological pH and temperature. The first goal of the study was to obtain the spectral parameters for characterization of the GSH-Gly signal under physiological conditions. The second goal was to investigate a new method of separating GSH-Gly from Glx in vivo. The characterization of the signal was carried out by utilization of numerical simulations as well as experiments over a wide range of magnetic fields (4.0–14 T). The proposed separation scheme utilizes J-difference editing to quantify the Glx contribution to separate it from the GSH-Gly signal. The presented method retains 100% of the GSH-Gly signal. The overall increase in signal to noise ratio of the targeted resonance is calculated to yield a significant SNR improvement compared to previously used methods that target GSH-Cys residue. This allows shorter acquisition times for in vivo human clinical studies. 相似文献
945.
We study propagation of surface electromagnetic waves along a metallic surface covered by various layered dielectric structures.
We show that strong radiative losses, typical for scattering of a surface wave, can be considerably suppressed when a single
dielectric step is substituted by gradient index or periodic layered structure. 相似文献
946.
A.?Spad?o E.?Otón R.?D?browski M.??urowska J.?M.?Otón N.?Bennis 《Opto-Electronics Review》2010,18(2):219-222
Electrooptical properties of several new orthoconic antiferroelectric liquid crystal mixtures with partially fluorinated alkoxyalkoxy
terminal chains have been investigated in order to select the best mixture for display applications. Electrooptical studies
have been performed on these orthoconic materials aiming at evaluating their static and dynamic performance under passive
multiplexing conditions. A number of parameters have been evaluated, static and dynamic contrast, driving scheme for passive
multiplexing, rise and fall response times, dynamic range, and dynamic greyscale. 相似文献
947.
J.?Piotrowski J.?Pawluczyk A.?Piotrowski W.?Gawron M.?Romanis K.?K?os 《Opto-Electronics Review》2010,18(3):318-327
The history, status, and recent progress in the middle and long wavelength Hg1−xCdxTe infrared detectors operating at near room temperatures are reviewed. Thermal generation of charge carriers in narrow gap
semiconductor is a major limitation or sensitivity. Cooling is a straightforward way to suppress thermal generation of charge
carriers and reduce related noise. However, at the same time, cooling requirements make infrared systems bulky, heavy, and
inconvenient in use. A number of concepts to improve performance of photodetectors operating at near room temperatures have
been proposed and implemented. Recent considerations of the fundamental detector mechanisms suggest that near perfect detection
can be achieved without the need for cryogenic cooling. This paper, to a large degree, is based on the research, development,
and commercialization of uncooled HgCdTe detectors in Poland. The devices have been based on 3D-variable band gap and doping
level structures that integrate optical, detection and electric functions in a monolithic chip. The device architecture is
optimized for the best compromise between requirements of high quantum efficiency, efficient and fast collection of photogenerated
charge carriers, minimized thermal generation, reduced parasitic impedances, wide linear range, wide acceptance angles and
other device features. Recent refinements in the devices design and technology have lead to sensitivities close to the background
radiation noise limit, extension of useful spectral range to > 16 μm wavelength and picosecond range response times. The devices
have found numerous applications in various optoelectronic systems. Among them there are fast scan FTIR spectrometers developed
under MEMFIS project. 相似文献
948.
Precursor kinetics and its influence on MOCVD growth was investigated using an infrared absorption gas analyser. After several
refinements, the analyser was able to be used to measure time dependent concentrations of precursors in the growth zone. Changes
were induced by periodic switching of corresponding bubbler valves. It was proved that precursor transport could be accurately
described by the combined plug flow and perfectly mixed tank model. The studies of the precursor trans-port are strategically
important for the growth of multilayer structures, when growth time of particular layers becomes comparable to delays and
time constants. One example is quantum wells or interdiffused multilayer process (IMP) used in the growth of Hg1-xCdxTe heterostructures,
where knowledge of precursor transport characteristics is vital for understanding and properly designing that growth. The
model parameters, sc. the delays and time constants for DIPTe and DMCd, were evaluated for various growth conditions and then
successfully used to optimise the growth of complex Hg1−xCdxTe heterostructures. 相似文献
949.
Tommi Kaplas Kari Laitinen Tuula Moilanen Yrj? Tolonen Kristoffer Albrecht Raimo Silvennoinen 《Optical Review》2010,17(3):252-256
Traditional Japanese woodblock printing is a centuries old art form. This time-honoured form of art is at risk of extinction
as a consequence of the increasing lack of availability of wild cherry trees, which are a traditionally used woodblock material.
Solutions for this material problem have been investigated for several years, but none of the tested materials has been sufficient
when compared with the watercolour print quality imprinted by wild cherry woodblocks. To contribute to overcoming this material
problem, we have investigated the physical properties of heat-treated woodblock materials made from different wood species.
The International Commission on Illumination (CIE) tristimulus values, the CIELAB coordinates, the total reflectance, and
the gloss, as well as, the water contact angle from the woodblock surface is observed to have a strong relation to the surface
treatment of a woodblock. The surface treatment of a woodblock, in turn, relates to its water delivery, which is the basis
for watercolour printing. 相似文献
950.
The significance of the electron–phonon interaction for optically stimulated luminescence (OSL) process in quartz is demonstrated. OSL variation with temperature has been investigated for four samples of natural quartz. Changes of the OSL decay rate have been observed for all components of the OSL signal. The scale and tendency of these changes are comparable with outcomes of computer simulations carried out for the model composed of two deep electron traps, one shallow trap and one recombination centre, taking into account the electron–phonon interactions. 相似文献