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1.
分析了含单负材料的光量子阱结构中的振荡透射模的性质.用两种单负(负介电常量或负磁导率)材料交替周期堆叠形成的两个光子晶体构造了一维光量子阱结构,该结构中仅其中一个光子晶体含有零有效位相带隙.数值计算结果发现,在零有效位相带隙内存在振荡透射模.通过改变井区域光子晶体内单负材料层的厚度及周期数,振荡透射模的数目、频率及频率间隔均可调节.振荡透射模对入射角度的依赖均很弱;随着入射角度的改变,缺陷模频率的相对改变量保持在0.02以下.该研究结果可用于设计多通道全向滤波器. 相似文献
2.
Uniform and symmetric resonance modes (known as Aharoni’s exchange resonance modes) are derived from micromagnetic equilibrium condition in the linear approximation. To investigate the uniform and symmetric resonance modes in ferromagnetic nanoscale grains, the microwave permeability of FeCo-based nanocrystalline alloy particles/paraffin composites was measured and calculated in the range 0.5-18 GHz. The measured dynamic permeability curves exhibit a broad resonance band at 4-6 GHz; some curves also exhibit a narrow resonance band at 13 GHz. The former behavior is in qualitative agreement with the uniform mode, and the latter is attributed to the first eigenvalue mode of the symmetric resonance modes excited in nanocrystalline monodomain grains in FeCo-based alloys. The difference value (Δω11) between the uniform resonance frequency and the first frequency eigenvalue of the symmetric resonance modes shows good agreement with experiment. 相似文献
3.
A. Soltani Vala S. Roshan Entezar A. A. Sedghi 《The European Physical Journal B - Condensed Matter and Complex Systems》2011,81(3):269-274
By virtue of the efficiency of the Dirichlet-to-Neumann
map method, the details of the band structure of a two-dimensional
square lattice photonic crystal composed of dispersive metamaterial
circular rods in air background has been studied.
We show that there are two flat bands at the band structure
of the system for both H-polarization and E-polarization. These flat bands are created around the
magnetic resonance frequency, surface plasmon frequency and magnetic surface plasmon frequency. We realized that
the modes with frequencies lying above
the resonance frequency behave like resonant cavity modes created in
a single metallic cylindrical waveguide. While, due to the
relatively large and imaginary refractive index of the metamaterial
rods at the frequencies lying below the resonance frequency, the
modes are localized modes with negligible penetration into the rods.
Moreover, the modes are localized at the interface of the
cylindrical metamaterial rods and the air background
for the frequencies around the surface plasmon frequency and the magnetic surface plasmon frequency. 相似文献
4.
Topi Uusitalo Heikki Virtanen Paolo Bardella Mihail Dumitrescu 《Optical and Quantum Electronics》2017,49(1):46
The paper explores the possibilities to extend the direct modulation bandwidth in dual-longitudinal-mode distributed feedback lasers by exploiting the photon–photon resonance induced by the interaction of the two modes in the laser cavity. The effects on the direct amplitude modulation and on the direct modulation of the difference frequency between the two modes are analyzed using simulation and experimental results. When the photon–photon resonance, which occurs at the difference frequency between the two modes, is properly placed at a higher frequency than the carrier-photon resonance, the small-signal amplitude modulation (AM) bandwidth of the laser can be significantly increased. However, both simulations and experiments point out that a high small-signal AM bandwidth does not lead to a high large-signal AM bandwidth if the small-signal modulation response has significant variations across the modulation bandwidth. The paper shows that a high large-signal AM bandwidth is obtained when the two modes are significantly unbalanced, whereas a high-bandwidth difference frequency modulation can be best detected when the two modes are balanced and the DC bias is properly chosen. 相似文献
5.
We show that, when the longitudinal confinement factor in an edge-emitting laser is treated as a dynamic variable, the modulation transfer function has an extra term. This term produces a supplementary photon?Cphoton resonance peak in the modulation response at a frequency corresponding to the frequency separation between longitudinal modes, when these modes are phase-locked long enough (quasi-phase-locked). The photon?Cphoton resonance peak is strongest when two consecutive quasi-phase-locked dominant longitudinal modes have similar longitudinal envelopes and share equally the photon population. 相似文献
6.
7.
Enkrich C Wegener M Linden S Burger S Zschiedrich L Schmidt F Zhou JF Koschny T Soukoulis CM 《Physical review letters》2005,95(20):203901
Arrays of gold split rings with a 50-nm minimum feature size and with an LC resonance at 200 THz frequency (1.5 microm wavelength) are fabricated. For normal-incidence conditions, they exhibit a pronounced fundamental magnetic mode, arising from a coupling via the electric component of the incident light. For oblique incidence, a coupling via the magnetic component is demonstrated as well. Moreover, we identify a novel higher-order magnetic resonance at around 370 THz (800 nm wavelength) that evolves out of the Mie resonance for oblique incidence. Comparison with theory delivers good agreement and also shows that the structures allow for a negative magnetic permeability. 相似文献
8.
We introduce a novel broadband optical frequency comb generator consisting of a parametric oscillator with an intracavity electro-optic phase modulator. The parametric oscillator is pumped by 532-nm light and produces near-degenerate signal and idler fields. The modulator generates a comb structure about both the signal and the idler. Coupling between the two families of modes results in a dispersion-limited comb that spans 20 nm (5.3 THz). A signal-to-noise ratio of >30 dB in a 300-kHz bandwidth is observed in the beat frequency between individual comb elements and a reference laser. 相似文献
9.
Passively mode-locked erbium doped fiber ring laser was investigated. We present optimization of laser configuration where
nonlinear polarization rotation was used for modes synchronization. Simulations of pulse propagation inside a laser cavity
were applied in order to confirm the optimisation technique. Experimental results are presented and more than 32-nm spectral
width of the output frequency comb was obtained. 相似文献
10.
Vibro-acoustography technique known by its noncontact excitation was used to detect resonance frequencies of objects in water. Two intersecting ultrasound beams generated by a 40 mm-diameter annular array transducer, focused at 35 mm and driven at f1=2.2 MHz and f2=2.22 MHz respectively, were targeted inside the object under test to produce a radiation force beating at the difference frequency f2-f1. This low frequency radiation force was used to excite the resonance vibration modes of the object by sweeping the frequency f2 between 2.22 and 2.275 MHz. The amplitude of the acoustic emission produced by the vibrations of the object was detected by a low frequency hydrophone (BW=60 kHz). By this approach, it was possible to detect resonance frequencies through amplitude variations of the measured acoustic emission. Experiments were conducted in a water tank for objects of different shapes and sizes. With a chalk sphere (15 mm-diameter) two resonance frequencies were detected at 45.75 and 68.75 kHz, and with a cylinder (10.38 mm-diameter and 32.20 mm-length) four principal resonance frequencies were identified in the 60 kHz-bandwidth of the hydrophone. It was shown with finite element calculations performed with Ansys, in which both solid and fluid parts were modelled, that the measured resonance frequencies corresponded to compressional or dilatation vibration modes of the object. It was verified that shear waves generated by torsional vibration modes were not propagated in water, as it is well known. The use of this technique to characterize heterogeneities in different media seems to be relatively more advantageous to other ultrasonic methods. 相似文献
11.
Calculations of three-dimensional magnetic excitations in permalloy nanostructures with vortex state
Bin Zhang 《Journal of magnetism and magnetic materials》2010,322(17):2480-2484
Dynamic susceptibility spectra of the vortex state in nanorings and nanodots are studied using three-dimensional micromagnetic simulations. Spatial maps of the susceptibility have enabled identification of various resonance modes. For an exciting field along the x axis, several resonance peaks appear for a thin dot, including a core mode, whereas only one main resonance peak is detected for a ring corresponding to a volume mode with uniform magnetization perpendicular to the exciting field (x direction). A low-frequency resonance peak related to a surface mode and a high-frequency resonance peak viewed as an edge mode are additionally observed for a thick ring. These three resonance modes (surface, volume and edge modes) which correspond to low, intermediate and high-frequency resonance peaks, respectively, are also captured for an exciting field along the y axis. In addition, a mixed edge and volume mode is revealed at a higher frequency. 相似文献
12.
Z. D. Kvon D. A. Kozlov S. N. Danilov C. Zoth P. Vierling S. Stachel V. V. Bel’kov A. K. Bakarov D. V. Dmitriev A. I. Toropov S. D. Ganichev 《JETP Letters》2013,97(1):41-44
The terahertz response of a high-density and high-mobility two-dimensional electron gas in 13-nm GaAs quantum wells at frequencies of 0.7 and 1.63 THz has been investigated. Terahertz radiation-induced magnetoresistance oscillations have been discovered. The oscillation maxima coincide with the harmonics of cyclotron resonance. It has been shown that a large number of harmonics (up to the ninth) appear under irradiation at a frequency of 0.7 THz. In this case, the effect is the analogue of microwave-induced oscillations. At a higher frequency, the oscillation amplitude decreases drastically with an increase in the harmonic number. This indicates a transition to the regime of ordinary cyclotron harmonics. 相似文献
13.
P.H. Tan C.Y. Hu J. Dong W.C. Shen 《Physica E: Low-dimensional Systems and Nanostructures》2007,37(1-2):93
Resonant Raman scattering of second-order Raman modes from an individual graphite whisker synthesized by a high-temperature heat-treatment method at a special pressure was discussed here. The dependence of phonon frequencies on the incoming laser light and the frequency difference between Stokes and anti-Stokes scattering show their origin from double resonance Raman scattering. Our results show that all the experimental results of second-order Raman modes in graphite whiskers, such as the excitation-energy dependence on the mode frequency, the frequency shift between a second-order Raman mode and its fundamentals, and the frequency discrepancy between Stokes and anti-Stokes components of a second-order Raman mode can be well understood by double resonance Raman scattering. 相似文献
14.
Optical frequency division by 3 of 532 nm is demonstrated by back-to-back difference-frequency generation in a periodically poled lithium niobate crystal with a double grating. The first grating generates 1596-nm light from 532- and 798-nm inputs, and the second grating mixes the 798-nm input and the 1596-nm output from the first grating to produce a second 1596-nm output. The beat signal between the two 1596-nm outputs is detected and frequency stabilized to yield the 3:1 frequency ratio. 相似文献
15.
A nonlinear version of resonance ultrasound spectroscopy (RUS) theory is presented. This is important for NDT-purposes as damage manifests itself more pronounced and in an earlier stage by changes in the nonlinear elastic constants. General equations are derived for the 1-D case, describing the interaction between the modes due to the presence of nonlinearity. An analytical solution of these equations is derived which predicts the shift of the resonance frequency versus amplitude in a bar with localized damage. The damage was modelled as a finite region, having a constant cubic nonlinearity, in an otherwise linear 1-D bar. The analytical expressions for the shifts in resonance frequency at different modes were used to infer information about the position, nonlinearity and width of the damage. Unlike other techniques, the proposed method does not require scanning to locate the defect, as it lets the different modes, each with a different vibration pattern, probe the structure. 相似文献
16.
Akimov DA Serebryannikov EE Zheltikov AM Schmitt M Maksimenka R Kiefer W Dukel'skii KV Shevandin VS Kondrat'ev YN 《Optics letters》2003,28(20):1948-1950
Phase-matched four-wave mixing in higher-order modes of microstructure fibers allows unprecedentedly high efficiencies of anti-Stokes frequency conversion to be achieved for subnanojoule femtosecond laser pulses. 70-fs pulses of 790-nm radiation were used to generate an anti-Stokes component at 520-530 nm in a higher-order mode of a microstructure fiber with a 4.8-microm core. The maximum ratio of the anti-Stokes signal energy to the energy of the pump component in the output spectrum is estimated as 1.7. 相似文献
17.
同时考虑一维梁结构的弯曲和轴向振动,对其压电阻抗模型进行建模分析和试验验证。在0.02~42 kHz频段内区分并标记了一维钢梁弯曲振动模态前18阶及轴向振动模态前3阶。结果表明:在0.02~7.5kHz频段内,数值计算和试验结果中谐振峰对应频率的相对误差较大:11.7%~16.5%,其原因可能是低频时振动能量较低且波的传播受结构阻尼、边界条件及环境噪音等因素影响较为明显;在7.5~42kHz范围内,两者谐振峰位置符合良好,相对误差较小:0.11%~2.31%,表明该模型在高频段具有较好的适用性;轴向振动模态对应频率大于弯曲振动模态。本研究为结构健康监测过程中检测频段的选取及损伤信息的提取提供参考。 相似文献
18.
Piacsek AA Abdul-Wahid S Taylor R 《The Journal of the Acoustical Society of America》2012,131(6):EL506-EL512
Measurements of the vibrational response of a spherical aluminum shell subject to changes in the interior pressure clearly demonstrate that resonance frequencies shift higher as the pressure is increased. The frequency shift appears to be smaller for longitudinal modes than for bending wave modes. The magnitude of frequency shift is comparable to analytical predictions made for thin cylindrical shells. Changes in the amplitudes of resonance peaks are also observed. A possible application of this result is a method for noninvasively monitoring pressure changes inside sealed containers, including intracranial pressure in humans. 相似文献
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20.
提出了用波导本征模展开的方法计算射频调制的短脉冲电子束在矩形波导中的自发辐射。模展开系数决定了辐射进入TE0n模的功率。将短脉冲理想化为时间上的d函数,可以发现当辐射频率正好等于用来调制电子束的射频的整数倍时,辐射模式表现为“纯”的波导本征模,此时辐射功率最强。用此方法估算了设计中的上海远红外波导自由电子激光器的辐射功率。 相似文献