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排序方式: 共有310条查询结果,搜索用时 15 毫秒
21.
Emil S. Koteles 《Fiber and Integrated Optics》1999,18(4):211-244
A review is presented of state-of-the-art optical planar waveguide demultiplexers (DEMUXes), that is, phasars (arrayed waveguide) and etched grating devices designed for high-density (narrow channel spacing) wavelength division multiplexing (WDM) systems. Their advantages and disadvantages are discussed in comparison with other techniques for demultiplexing WDM signals. The advances made in their performance are reviewed, and ultimate limitations, set by technological constraints, are proposed. Finally, a comparison is made of the advantages and disadvantages of etched grating as opposed to phasar planar waveguide DEMUXes. 相似文献
22.
23.
Jin Tae Kim 《Optics Communications》2011,284(18):4171-4175
It has been experimentally demonstrated that a low-loss guided hybrid mode is supported if a metal strip is embedded in a low index polymer layer surrounded by two high index slabs. In this paper, further numerical analyses on the guided hybrid modes are reported to fully elucidate the characteristics of the hybrid plasmonic waveguide. For a one-dimensional slab structure with a metal film of infinite width, simulation results exhibit that low-loss guided hybrid modes are associated with surface plasmon modes and dual dielectric slab modes. The optical properties of the guided modes are improved by increasing the field intensity which is confined into lossless dielectric layers by decreasing the metal film thickness and increasing the refractive index and thickness of the high-index slabs. The finite element method is used to investigate the lateral mode confinement of the optical guided modes by the corresponding metal strip. By reducing the metal film width, the guided modes are confined in the plane transverse to the direction of propagation and the characteristics are significantly improved. The hybrid plasmonic waveguide can be exploited for long-range propagation-based application such as optical interconnection. 相似文献
24.
Based on the coordinate transformation theory, we propose a way to manipulate the field distribution in three-dimensional waveguides filled with the designed material. In this work, we show that the designed transformation media can concentrate the electromagnetic field more extremely around the center of the rectangular cross-section inside the straight waveguide. Furthermore, high concentration of the field distribution inside the waveguide bend is also performed well. Numerical simulations demonstrate that the electromagnetic wave can propagate without any signal destruction and conserve the original propagation mode at receiver side. 相似文献
25.
S.V. Kozhevnikov A. RühmF. Ott N.K. PleshanovJ. Major 《Physica B: Condensed Matter》2011,406(12):2463-2466
A neutron waveguide is a three-layer structure in which a guiding layer with low optical potential is placed between two cladding layers with high optical potential. Under proper operation conditions, the neutron density is resonantly enhanced inside the guiding layer. In our experimental scheme, the neutron beam enters through the surface of the top layer at glancing angle and goes out from the edge of the guiding layer, with an angular distribution corresponding to Fraunhofer diffraction from a narrow slit. The incident neutron beam is relatively wide (0.1 mm) and highly collimated (0.01°). The outgoing sub-micron beam is extremely narrow at the outlet (0.1 μm) and more divergent (0.1°). So far only the production of unpolarized sub-micron neutron beams has been reported. Here we present first experiments on polarized sub-micron neutron beams. For these studies a polarized incident beam was used and two types of magnetic waveguides were investigated: a polarizing magnetic waveguide Fe(20 nm)/Cu(140 nm)/Fe(50 nm)//glass and a non-polarizing magnetic waveguide Py(10 nm)/Al(140 nm)/Py(50 nm)//glass (Py is permalloy). The waveguide samples were characterized by polarized neutron reflectometry. 相似文献
26.
In this paper, we propose complete radiation boundary conditions (CRBCs) for solutions of the convected Helmholtz equation with a uniform mean flow in a waveguide. We first study CRBCs for the Helmholtz equation in a waveguide. Noting that the convected Helmholtz equation is associated with the Helmholtz equation via the Prandtl–Glauert transformation, CRBCs for the convected Helmholtz equation is derived from CRBCs for the Helmholtz equation. We analyse well-posedness and convergence of approximate solutions satisfying CRBCs for the convected Helmholtz equation. In addition, simple numerical experiments will be presented to confirm the theoretical results. 相似文献
27.
D. Pasquet J. L. Gautier P. Pouvil 《International Journal of Infrared and Millimeter Waves》1986,7(3):357-364
Very simple analytical expressions are proposed for the reflection coefficients of coupling holes used in FIR waveguide lasers. The relations are carried out for dielectric and metallic circular waveguides. 相似文献
28.
A single-ridge waveguide with a symmetrical longitudinal trough, designated as a ridge-trough waveguide has been used as a transition in a V-band (50-75 GHz) wafer probe recently. In this paper, the field patterns for the dominant TE mode and the first higher TE mode in ridge-trough waveguide with different configurations are presented by finite element method. The field patterns in this paper have important values for us to understand the transmission characteristics of ridge-trough waveguide, and will be of practical significance in designing ridge-trough waveguide components in microwave and millimeter wave engineering. 相似文献
29.
Michael D. Lesoine Jonathan M. Bobbitt Shaobin Zhu Ning Fang Emily A. Smith 《Analytica chimica acta》2014
A scanning angle (SA) Raman microscope with 532-nm excitation is reported for probing chemical content perpendicular to a sample interface. The instrument is fully automated to collect Raman spectra across a range of incident angles from 20.50 to 79.50° with an angular spread of 0.4 ± 0.2° and an angular uncertainty of 0.09°. Instrumental controls drive a rotational stage with a fixed axis of rotation relative to a prism-based sample interface mounted on an inverted microscope stage. Three benefits of SA Raman microscopy using visible wavelengths, compared to near infrared wavelengths are: (i) better surface sensitivity; (ii) increased signal due to the frequency to the fourth power dependence of the Raman signal, and the possibility for resonant enhancement; (iii) the need to scan a reduced angular range to shorten data collection times. These benefits were demonstrated with SA Raman measurements of thin polymer films of polystyrene or a diblock copolymer of polystyrene and poly(3-hexylthiophene-2,5-diyl). Thin film spectra were collected with a signal-to-noise ratio of 30 using a 0.25 s acquisition time. 相似文献
30.
Planar and buried channel porous silicon waveguides (WG) were prepared from p+-type silicon substrate by a two-step anodization process. Erbium ions were incorporated into pores of the porous silicon layers by an electrochemical method using ErCl3-saturated solution. Erbium concentration of around 1020 at/cm3 was determined by energy-dispersive X-ray analysis performed on SEM cross-section. The luminescence properties of erbium ions in the IR range were determined and a luminescence time decay of 420 μs was measured. Optical losses were studied on these WG. The increased losses after doping were discussed. 相似文献