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651.
Time-resolved imaging of mode-conversion process of terahertz transients in subwavelength waveguides
Yao Lu Qiang Wu Qi Zhang Ri-De Wang Bin Zhang Wen-Juan Zhao Deng Zhang Hao Xiong Cheng-Liang Yang Ji-Wei Qi Chong-Pei Pan Jing-Jun Xu 《Frontiers of Physics》2019,14(4):42502
We studied the mode-conversion process of terahertz pulses from a planar subwavelength waveguide to a tilted rectangular subwavelength waveguide. An unusual wavefront rotation, which led to an extra conversion time, was observed using a time-resolved imaging technique. We simulated the mode conversion process by a finite-difference time-domain method, and the results agreed well with the experiments. According to the simulations, the conversion time was demonstrated to become longer as the tilt angle or width of the rectangular waveguide increased. This work provides the possibility to optimize the future high-speed communications and terahertz integrated platforms. 相似文献
652.
An interest in energy transport in 3D chains of metal nanoparticles is oriented towards future applications in nanoscale optical
devices. We consider plasmonic waveguides composed of silver nanoplates arranged in several geometries to find the one with
the lowest attenuation. We investigate light propagation of 500-nm wavelength along different chains of silver nanoplates
of subwavelength length and width and wavelength-size height. Energy transmission of the waveguides is analysed in the range
of 400–2000 nm. We find that chain of short parallel nanoplates guides energy better than two electromagnetically coupled
continuous stripes and all other considered nonparallel structures. In a wavelength range of 500–600 nm, this 2-μm long 3D
waveguide transmits 39% of incident energy in a channel of λ × λ/2 cross section area. 相似文献
653.
654.
Roman Gl?ckler 《International Journal of Infrared and Millimeter Waves》1990,11(2):101-110
A phased array is presented at a frequency of 70 GHz, consisting of a corporate feed, ferrite phase shifters and dielectric rod antennas. Metal waveguides were utilized to construct the feed network, whereas a special dielectric waveguide structure was employed for the ferrite phase shifter and dielectric rod antenna. Beam scanning can be performed electronically controlled in the horizontal plane. 相似文献
655.
M. Casalboni F. Belli M. Cirillo F. De Matteis P. Prosposito R. Russo R. Pizzoferrato 《Journal of Sol-Gel Science and Technology》2003,26(1-3):937-941
In this contribution we report on the preliminary results of synthesis and characterization of both planar and strip-loaded waveguides on silicon substrates. All the layers (buffer, guiding and cladding) have been grown by one step spin-coating process using hybrid organic/inorganic sol-gel route. Their thickness ranges from less than 1 m, for the cladding layer, up to 4 m, for the buffer one. The refractive index of the different planar waveguides were measured by means of m-line technique. Layer interfaces have been investigated with secondary ion mass spectroscopy (SIMS). Photolithography and reactive ion etching (RIE) technique have been employed to pattern the strip-loaded structures. Optical and scanning electron microscopy analysis was performed to evaluate their shape. Preliminary longitudinal transmission measurements for strip-loaded waveguides are also reported. 相似文献
656.
Manfred Thumm Helga Kumric 《International Journal of Infrared and Millimeter Waves》1989,10(9):1059-1075
Elliptical deformation of oversized, smooth-wall circular waveguides can produce choosable elliptical or circular polarization from a linearly polarized TE11 or TM11 mode used as intermediate linearly polarized modes in TEO1 to HE11 mode conversion sequences in electron cyclotron resonance heating (ECRH) of magnetically confined thermonuclear fusion plasmas with high-power gyrotrons. Mode coupling in elliptically distorted overmoded circular waveguides has been studied theoretically and experimentally in order to optimize TE11 (and TM11) polarizers (I.D.=27.79 mm) for the 1 MW/70 GHz long-pulse (3s) ECRH system on the Garching Stellarator W VII-AS. Coupling coefficients for ellipticity coupling of non-degenerate modes are given (coupled-mode differential equations formalism). The polarization converters essentially consist of smooth-wall circular waveguides which are gradually squeezed. A sine-squared function of the length coordinate is used to get an almost elliptical crosssection in the middle and circular cross sections at both ends. Arbitrary elliptical polarization states can be generated introducing an extremely low level (<<1%) of undesired spurious modes. Well defined differential phase characteristics have been achieved. 相似文献
657.
用有效折射率法和有限元法分析多量子阱条形光波导 总被引:5,自引:2,他引:3
本文提出了一种快速和精确分析多量子阱(MQW)条形光波导的新算法。它基于有效折射率法和有限元法的结合。首先,由等效的平面波导替换多量子阱条形结构,用有效折射率法从原来问题得到平面波导的折射率分布;然后,用有限元法计算等效结构中E_(mn)~x模和E_(mn)~y模的传播常数和场强分布。文中给出了任意阱数和不同宽度多量子阱的对称结构和不对称结构的结果。 相似文献
658.
Using convenient parameters, the mode propagation constants in hollow circular waveguides with low-conductivity wall material are derived into practical formulas. The variations of these propagation constants versus electrical characteristics of the wall material are studied. The results allow the determination of optimal materials for low-loss mode transmission and the improvements achieved with these optimal materials compared to the usual dielectrical materials are pointed out. Application to the particular case of ordinary glass as a guide wall material is made. The condition to have the fundamental EH11 mode the less attanuated is given. 相似文献
659.
The analytical expression for the transmission spectra of coupled cavity waveguides (CCWs) in photonic crystals (PCs) is derived based on the coupled-mode theory (CMT). Parameters in the analytical expression can be extracted by simple numerical simulations. We reveal that it is the phase shift between the two adjacent PC defects that uniquely determines the flatness of the impurity bands of CCWs. In addition, it is found that the phase shift also greatly affects the bandwidth of CCWs. Thus, the engineering of the impurity bands of CCWs can be realized through the adjustment of the phase shift. Based on the theoretical results, an interesting phenomenon in which a CCW acts as a single PC defect and its impurity band possesses a Lorentz lineshape is predicted. Very good agreement between the analytical results and the numerical simulations based on transfer matrix method has been achieved. 相似文献
660.
1.IntroductionOpticalspatialsolitoninduced-waveguidesareofgreatresearchinterestrecently[1-8]becauseoftheirPOtentialapplicationinopticalcommunicationsandopticalcompution.Asoliton--inducedwaveguidecanguidelightinself--focusingorself--defocusingKerr-typemediabecausethesolitonbeaminducesarefractive-indexprofileequivalenttoanordinarydielectricwaveguide.Soliton-inducedwaveguidecansupPOrtmanymodesofaprobebeampropagatingcoaxiallyalongthesolitonwaveguideSoliton-inducedwaveguideshaveadvantageovertheir… 相似文献