Mode Resonance Conditions Research Articles

Investigation of wide-range refractive index sensor based on asymmetric metal-cladding dielectric waveguide structure

A refractive index (RI) sensor based on an asymmetric metal-cladding dielectric waveguide structure, in which an analyte is used as the guiding layer, is proposed in this report. The angular scanning attenuated total reflection spectra of the sensor and optical field distributions under waveguide mode resonance conditions were simulated, which confirmed that multiple waveguide modes can be used for sensing, and that different waveguide modes exist in different analyte RI ranges. The curves of both waveguide mode resonance angles and the sensitivity as a function of the analyte RI demonstrated that a wide sensing range can be achieved by combining waveguide modes of different orders. The proposed sensor could be applied to numerous fields, such as biological and chemical detection.

Electronically switchable compact quad-band microstrip bandpass filter using varactor perturbed dual-mode resonators

In this paper, an electronically switchable quad-band microstrip bandpass filter is designed using varactor perturbed dual-mode resonators. For this purpose, four meandered dual-mode square loop resonators (DMSLRs) having reference patches are nested and varactor diodes are used to serve as perturbation elements. The designed resonator is analyzed by deriving even/odd mode resonance conditions. S-parameters are also calculated according to the even and odd mode input impedances. Stub loaded feedlines are used to couple the DMSLRs to Input/Output (I/O) ports. According to the capacitances of varactor diodes, each passband can be independently turned on and off. Coupling scheme and coupling matrix of the designed filter are introduced to realize the coupling descriptions. Switching operations are also investigated over the frequency responses obtained from coupling matrix. Passbands of the filter are adjusted to 1.4, 1.7, 2.25, and 2.7 GHz. The designed filter was also fabricated and measured results show a good agreement with the simulated and theoretical results.

Effect of guide field on three-dimensional electron shear flow instabilities in electron current sheets

We examine, in the limit of electron plasma ${\it\beta}_{e}\ll 1$, the effect of an external guide field and current sheet thickness on the growth rates and nature of three-dimensional (3-D) unstable modes of an electron current sheet driven by electron shear flow. The growth rate of the fastest growing mode drops rapidly with current sheet thickness but increases slowly with the strength of the guide field. The fastest growing mode is tearing type only for thin current sheets (half-thickness ${\approx}d_{e}$, where $d_{e}=c/{\it\omega}_{pe}$ is the electron inertial length) and zero guide field. For finite guide field or thicker current sheets, the fastest growing mode is a non-tearing type. However, growth rates of the fastest 2-D tearing and 3-D non-tearing modes are comparable for thin current sheets ($d_{e}<\text{half thickness}<2\,d_{e}$) and small guide field (of the order of the asymptotic value of the component of magnetic field supporting the electron current sheet). It is shown that the general mode resonance conditions for tearing modes depend on the effective dissipation mechanism. The usual tearing mode resonance condition ($\boldsymbol{k}\boldsymbol{\cdot }\boldsymbol{B}_{0}=0$, $\boldsymbol{k}$ is the wavevector and $\boldsymbol{B}_{0}$ is the equilibrium magnetic field) can be recovered from the general resonance conditions in the limit of weak dissipation. The conditions (relating current sheet thickness, strength of the guide field and wavenumbers) for the non-existence of tearing mode are obtained from the general mode resonance conditions. We discuss the role of electron shear flow instabilities in magnetic reconnection.

The Leaky Mode Resonance Condition Ensures 100% Diffraction Efficiency of Mirror-Based Resonant Gratings

The resonance condition of a leaky mode propagating in a dielectric multilayer, which is supported by a mirror and excited by a free-space wave from the cover medium, is simply derived from the phase of the reflection at the mirror and cover interfaces. The leaky mode resonance is used to obtain 100% first-order diffraction efficiency in a reflection resonant grating by destructive interference in the direction of Fresnel reflection. A number of examples support the validity of this condition for high efficiency and illustrate the usefulness of this intelligible representation of the diffraction phenomena for the synthesis of novel diffractive elements.

Temperature self-compensated lithium tantalate piezoelectric gyroscope for higher sensitivity and stability

A new H-type gyroscope using a single LiTaO 3 crystal that combines the H-type vibrational mode with a tuning fork type vibrational mode is proposed. This greatly suppresses leakage output from the piezoelectric gyroscope and also improves stability. The operation in the drive mode non-resonant condition and detection mode resonance condition is also proposed. It is possible to increase the sensor sensitivity remarkably because the drive voltage can be increased. In addition, an equivalent circuit constant including the leakage output could be accurately deduced. Automatic compensation of temperature characteristic for angular velocity detection sensitivity and drift is examined with the simple equivalent circuit. By adding a new sensor that detects the drive vibrational mode, we can produce a stable reference signal for the phase detection of output. This shows that it is possible to greatly improve the temperature characteristic of sensitivity and drift.

Magnon Analysis of Ferromagnetic Resonance in a Planer Ferrite, Zn2Y

The low power ferromagnetic resonance behavior at room temperature was measured on a magnetically anisotropic material, Zn 2 Y , with the object of studying relaxation processes on the basis of magnon manifold. The line-width of monocrystalline Zn 2 Y under a uniform mode resonance condition exhibits four kinds of maxima with increasing angle θ H of the applied d c field with respect to the crystallographic c axis. The first maximum is at θ H =0° and is small. The second maximum is the largest and extends over the entire region of θ H . The third and fourth maxima are small and attend on the larger angular tail of the second maximum. It may be concluded that the second maximum is due to the two-magnon decay of the uniform mode and the third due to the three-magnon decay of the uniform mode.