Resonant enhancement of dielectronic recombination by a microwave field

We have observed dielectronic recombination of Ba+ and e(-) from a continuum of finite bandwidth in the presence of microwave fields of frequencies 8.08 and 12.05 GHz and amplitudes of up to 2 V/cm. There are sharp resonant enhancements when the microwave frequency matches the Deltan = 1, 2, and 3 resonances of the intermediate autoionizing Rydberg states, and we attribute the enhancements to resonant microwave Stark l mixing. The microwave field provides a simple and powerful way to enhance the recombination rate for incident electrons of a specific energy.     

Resonant modal conversion in a two-mode waveguide

We characterize a system consisting of a two-mode waveguide coupled to a single-mode microring resonator possibly presenting a nonlinear response of Kerr type. By using the scattering parameter formalism extended to the multimode domain, we show that in the linear regime and for an ideally transparent medium, each resonance of the system can be exploited to perform complete even-to-odd (respectively, odd-to-even) modal conversion. Moreover, when the Kerr nonlinearity is effective, the microring enables a power-dependent modal switching mediated by phase bistability. Thanks to its mode-processing capabilities, this configuration is suitable to find application as a functional building-block in mode-division multiplexing (MDM) photonic integrated circuits.     

Resonant waveguide device with vertical gratings

Transmission resonant filters in a waveguide with vertical gratings have been realized in silicon on insulator wafers. Experimental studies of fabricated devices show a broad stopband of approximately 19 nm in the center of which exists a narrow transmission band of approximately 0.5 nm with a quality factor of approximately 3000. These resonant cavities are useful for laser cavities, switches, modulators, detectors, and tunable filters.     

Resonant radiation pressure on neutral particles in a waveguide

A theoretical analysis of electromagnetic forces on neutral particles in a hollow waveguide is presented. We show that the effective scattering cross section of a very small (Rayleigh) particle can be strongly modified inside a waveguide. The coupling of the scattered dipolar field with the waveguide modes induces a resonant enhanced backscattering state of the scatterer-guide system close to the onset of new modes. The particle effective cross section can then be as large as the wavelength even far from any transition resonance. As we will show, a small particle can be strongly accelerated along the guide axis while being highly confined in a narrow zone of the cross section of the guide.     

Resonant enhancement of low-contrast electro-optic effects

Ferroelectric liquid crystals can be optimized for speed, but such materials tend to have small switching angles and consequently low contrast in the smectic A(*) phase. We describe a method whereby such a low-contrast but fast-switching effect can be enhanced, in theory giving the same contrast as a material with a switching angle of 22.5 degrees . This method therefore promises liquid-crystal modulators of high contrast and with speeds of the order of hundreds of nanoseconds. The theoretical basis of this method and initial results that support this analysis are presented.     

扇形波导谐振宽边纵缝的归一化电导

扇形波导可作为高功率微波圆柱共形波导缝隙阵天线的基本单元。分析了扇形波导中主模场分量,根据实际情况对主模场进行了合理近似。采用互易定理推导由波导主模横向场分量和缝隙场分量表示的波导场分量的前向或后向散射系数。根据波导传输线理论,将波导宽边纵缝等效为并联导纳,再根据波导边界条件得到扇形波导宽边谐振纵缝的归一化电导与波导散射系数之间的关系式。根据缝隙天线与振子天线的互补关系得到扇形波导谐振缝隙的辐射阻抗,结合波导功率平衡关系得到由波导横向场散射系数表示的缝隙辐射功率表达式,得到归一化电导的与谐振宽边纵缝的偏移位置、缝隙宽度、波导波长以及扇形波导尺寸参数之间的解析表达式。给出了算例,在波导中间区域,通过商用软件计算得到的电导与理论公式结果基本吻合。     

扇形波导谐振宽边纵缝的归一化电导

扇形波导可作为高功率微波圆柱共形波导缝隙阵天线的基本单元。分析了扇形波导中主模场分量,根据实际情况对主模场进行了合理近似。采用互易定理推导由波导主模横向场分量和缝隙场分量表示的波导场分量的前向或后向散射系数。根据波导传输线理论,将波导宽边纵缝等效为并联导纳,再根据波导边界条件得到扇形波导宽边谐振纵缝的归一化电导与波导散射系数之间的关系式。根据缝隙天线与振子天线的互补关系得到扇形波导谐振缝隙的辐射阻抗,结合波导功率平衡关系得到由波导横向场散射系数表示的缝隙辐射功率表达式,得到归一化电导的与谐振宽边纵缝的偏移位置、缝隙宽度、波导波长以及扇形波导尺寸参数之间的解析表达式。给出了算例,在波导中间区域,通过商用软件计算得到的电导与理论公式结果基本吻合。     

Resonant reflection from a metal-coated insulating sphere in a waveguide

Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 31, No. 1, pp. 86–92, January, 1988.     

Sensitivity enhancement in optical waveguide sensors using metamaterials

In this paper, we show negative differential resistance (NDR) in CdSe quantum dot/MEH-PPV based nanocomposite multi-layer heterostructures at room temperature. The four-layer structure exhibited a maximum peak-to-valley ratio of current of 1190 at room temperature, while two-layer structures show a value of 4. Two-, three- and four-layer structures are studied. Each device configuration exhibits different kind of negative differential resistance. The possible mechanism is explained on the basis of tunneling phenomena.     

Resonant waveguide grating: Analysis of polarization independent filtering

We investigate the property of polarization independent reflection using a 1D grating. It is shown to be possible, by choosing the correct parameters of the structure and angle of incidence to adjust the bandwidth of the reflection curves for both polarizations in such a way that these coincide. We expect that the found polarization-independent narrow band filter can be used as a component for WDM applications.     

Resonant enhancement of tunneling magnetoresistance in double-barrier magnetic heterostructures

We show that spin-dependent resonant tunneling can dramatically enhance tunneling magnetoresistance. We consider double-barrier structures comprising a semiconductor quantum well between two insulating barriers and two ferromagnetic electrodes. By tuning the width of the quantum well, the lowest resonant level can be moved into the energy interval where the density of states for minority spins is zero. This leads to a great enhancement of the magnetoresistance, which exhibits a strong maximum as a function of the quantum well width. We demonstrate that magnetoresistance exceeding 800% is achievable in GaMnAs/AlAs/GaAs/AlAs/GaMnAs double-barrier structures.     

半圆形波导中的电磁场

利用矩形波导和圆形波导的结论,并结合叠加法和镜象法等工具,从理论上分析给出半圆形波导的TE波模型的电磁场分量.根据金属界面的特殊性质,在一定条件下运用叠加法的延拓求出半圆形波导的电磁场分量.最后通过过渡法对一般情况下半圆形波导的电磁场分量进行求解.     

Resonant enhancement of neutrinoless double-electron capture in 152Gd

In the search for the nuclide with the largest probability for neutrinoless double-electron capture, we have determined the Q(??) value between the ground states of (152)Gd and (152)Sm by Penning-trap mass-ratio measurements. The new Q(??) value of 55.70(18) keV results in a half-life of 10(26) yr for a 1 eV neutrino mass. With this smallest half-life among known 0ν?? transitions, (152)Gd is a promising candidate for the search for neutrinoless double-electron capture.     

Resonant enhancement of charge transfer through surface states

A model is proposed that treats electrons at surfaces as a combination of two-dimensional and three-dimensional degrees of freedom. This yields a simple formula for the surface state induced resonant enhancement of the transfer of electrons through a surface. The model also yields analytic approximations for the transition between two-dimensional and three-dimensional distance laws in the correlations between electrons in surface states. Received 6 August 2002 Published online 31 October 2002 RID="a" ID="a"e-mail: rainer@sask.usask.ca     

Resonant enhancement and dissipation in nonequilibrium van der Waals forces

Dispersion forces between molecules that are in relative motion, coupled to baths at different temperatures, or in excited states, are calculated using a Green function Liouville space expansion that extends the celebrated McLachlan response theory to the nonlinear regime. Our dynamical theory is applicable to systems that may be in any initial nonequilibrium state and that are subject to an arbitrary time-dependent coupling. In contrast to equilibrium forces which are attractive, nonequilibrium forces may be attractive or repulsive, exhibit chemically specific resonances, are far stronger, and may be nonconservative (with either positive or negative dissipation).     

Resonant enhancement of inelastic light scattering in strongly correlated materials

We use dynamical mean field theory to find an exact solution for inelastic light scattering in strongly correlated materials such as those near a quantum-critical metal-insulator transition. We evaluate the results for q=0 (Raman) scattering and find that resonant effects can be quite large, and yield a double resonance, a significant enhancement of nonresonant scattering peaks, a joint resonance of both peaks when the incident photon frequency is on the order of U, and the appearance of an isosbestic point in all symmetry channels for an intermediate range of incident photon frequencies.     

计算波导加载谐振腔谐振频率的新方法

基于边界元法,提出了一种新的简单有效的计算速调管输出系统波导加载腔的谐振频率、场分布的方法。计算了一种矩形波导加载矩形谐振腔的常见结构。利用主模TE10波激励,在波导的端口处采用推导出的Robin-type边界条件,通过扫频的方式,观测选定场点的值,极值对应系统的谐振频率。数值结果表明:波导加载谐振腔的谐振频率要低于同尺寸谐振腔的频率,谐振腔内的电场分布也受到耦合孔的影响。利用边界元法计算波导加载腔这样的半开放系统,具有实现简单、计算精确度高、数据输入少、计算时间短等优点。     

Resonant enhancement of the formation of hydrogen-helium muonic molecules

Formation of muonic molecules and , where J is rotational quantum number, in electron conversion process is investigated at collision energies between 0.004 eV and 50 eV. Corresponding reaction rates are calculated in adiabatic approximation for the three-body Coulomb problem. Significant enhancement of the rates for and is found near 7 eV and 30 eV, respectively. It is shown that the enhancement is due to resonances present in elastic and scattering at these energies. Acceleration of dμ atoms up to the resonant energy could be realized in triple H-D-³He mixture due to the muon transfer from protium to deuterium. Experimental investigation of nuclear synthesis from molecular state directly formed in the mixture is suggested.