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This paper investigates the mechanical behavior of micro scaled laminated composite plates based on the modified couple stress theory. To this aim, considering a displacement field for the plate, the kinematic parameters such as strains and curvatures are calculated. Utilizing these kinematic parameters, classical stresses and couple stresses are obtained in each layer and consequently the equation of motion is derived using equilibrium equations of forces and moment of forces. Equivalent mechanical properties including the length scale parameter are presented for the composite plate. Using these equivalent quantities, static deflection and natural frequency of bilayer microplates are investigated and effects of size dependency on the mechanical behavior of the structure are assessed. [ABSTRACT FROM AUTHOR]

In this paper, based on the size dependent theories, an accurate investigation for nonlinear dynamic analysis of electrostatically actuated microbridges is presented by using the nonlinear finite element formulation, analytical method and numerical approach. The microbridge used as a microresonator, is driven by simultaneously applied DC and AC voltages. In the framework of modified couple stress theory (MCST), the nonlinear equation of dynamic motion for this system is derived using extended Hamilton's principle. Thereupon, the nonlinear partial differential equation is converted to the nonlinear ordinary equation by Galerkin's method and solved by analytical and numerical techniques. The analytical solution for nonlinear vibration of the microresonators is obtained by perturbation theory. Findings show that the numerical and analytical results are in good agreement with each other. In order to make further verification of the analytical expression, a nonlinear nonclassical finite element formulation for dynamic deformation of the system is presented to calculate the time history results. The good agreement observed between the results of analytical method and nonlinear finite element simulation demonstrates that the procedures used in the analytical method such as Taylor expansion, one mode analysis and perturbation expansion in multiple scale approach are appropriate. By determining the frequency-response curves, the effects of size dependency on the amplitude of vibration and frequency position of the peak response are studied. Results show that considering the size dependent theory leads to notable decreasing of the amplitude of nonlinear vibration and approaching the frequency value of peak response to linear resonance frequency. [ABSTRACT FROM AUTHOR]

We have designed and experimentally demonstrated an integrated transverse electric (TE)-pass polarizer on silicon-on-insulator platform. The polarizer consists of an asymmetric coupling section where only the transverse magnetic (TM) mode is coupled to the cross-hybrid plasmonic waveguide and attenuated. The TE mode does not couple and passes through the polarizer. The polarizer was fabricated on the silicon-on-insulator platform. The device is 30 μm long, has a high extinction ratio of more than 28 dB over 150 nm bandwidth, and has a good fabrication tolerance. Most important, the proposed polarizer has an ultra-low insertion loss of less than 0.04 dB for the TE mode.

Using a newly proposed augmented low-index-guiding scheme with silicon nitride/silicon dual-core waveguide, we have designed, fabricated, and characterized a transverse electric (TE) to transverse magnetic (TM) and TM-to-TE compact polarization rotator. The polarization rotation is realized in an asymmetric directional coupler. The measured peak conversion efficiencies for the TE-to-TM and TM-to-TE rotations are approximately 97%. The measured polarization extinction ratio for the TE-to-TM rotation is greater than 20 dB over 50-nm bandwidth, while for the TM-to-TE rotation it is greater than 15 dB over the C-band.

This paper presents a new nonlinear model for coupled 3D displacements of the doubly-clamp microbeams based on the modified couple stress theory. The microbeam is assumed to deflect in axial and lateral directions and the nonlinearities caused by the mid-plane stretching are considered. Utilizing modified couple stress theory and applying extended Hamilton's principle, nonlinear equations of the coupled three-dimensional motion of the microbridge are derived. As case studies, the static deflection and nonlinear free vibration of the doubly-clamp microbeams are investigated using the presented model. For vibration analysis, the method of multiple scales is utilized to calculate the frequency of the microbridge versus the amplitudes of vibration in two lateral directions. The effects of the applied loads and amplitudes of vibration in each direction are investigated on the static deflection and frequencies of vibration respectively. Comparing the results obtained by classical and nonclassical theories shows that the classical theory underestimates the stiffness and natural frequency of the structures especially for microbeams that have thicknesses in order of the length scale parameter. Furthermore, findings shows that the mid-plane stretching causes a coupling between lateral directions so that applying load in one direction leads to change in deflection of the other direction. [ABSTRACT FROM AUTHOR]

We propose a compact polarization beam splitter (PBS) based on a silicon nitride enhanced silicon-on-insulator platform using an augmented low-index guiding (ALIG) waveguide structure. In the ALIG structure, the TM mode is mostly confined in the low-index silicon nitride, while the TE mode is confined in the high-index silicon. Since the two modes are confined in two separate layers, their properties can be controlled independently. The PBS is formed using an asymmetric multimode interference (MMI) section. The TM mode is directed to an output port by the ALIG waveguide, while the TE mode is coupled to the other output port via the multimode interferometer. Such a PBS has a very small footprint, low insertion loss, high polarization extinction ratio, and broadband response.

The signs of the imaginary parts of the permittivity and permeability in metamaterials such as split ring resonators and strip wires are investigated. It is shown that the Lorentzian model often used to describe the effective parameters (i.e., the permittivity and permeability) of these metamaterials does not physically allow their imaginary parts to be negative. Moreover, a popular technique used to retrieve the effective parameters of a structure from its S-parameters is also investigated. By comparing the effective parameters for an array of dielectric spheres obtained both from S-parameter simulations and analytical calculations, it is shown that an often observed negative imaginary permittivity obtained from the S-parameters is a result of numerical error in the simulations. This is shown both for the finite element method and finite-difference time-domain simulations.

We have experimentally and computationally studied the integration of a microstrip patch antenna with a two-dimensional photonic crystal substrate. This antenna was fabricated on a defect in the two-dimensional photonic crystal lattice that localized the energy under the patch antenna. The finite-difference time-domain method was employed to study the characteristics of this antenna. Measurements are in excellent agreement with calculations. The effects of finite size ground planes were also studied. This work can lead to a new design tool for integrating patch antennas with photonic crystal substrates.

We experimentally demonstrate a transverse electric (TE)-pass polarizer using the recently proposed hybrid plasmonic waveguide. The device consists of a silicon film separated from a chromium layer by a silica spacer. The device was characterized using a tunable laser in the 1.52–1.58 μm wavelength range. For a 30 μm long polarizer, the extinction ratio in this wavelength range varies from 23 to 28 dB and the insertion loss for the TE mode is 2–3 dB. The device is compact; its fabrication is completely compatible with silicon-on-insulator technology, and its performance compares favorably against previously reported silicon-based integrated optic TE-pass polarizers.

Hybrid plasmonic waveguides consisting of a high-index slab separated from a metal plane by a low-index spacer provide an optimal compromise between the loss and confinement for surface plasmon waves in passive medium. In such hybrid structures, because power for the TE and TM modes are concentrated in two different regions of the guide, the characteristics of the two modes can be controlled independently by changing the waveguide dimensions. We propose to use this property to implement a hybrid plasmonic polarization-independent directional coupler for a silicon on insulator platform. We also investigate the effects of variations of wavelength and device dimensions on the performance of the proposed device.

Hybrid plasmonic waveguides consisting of a metal plane separated from a high-index medium by a low-index spacer have recently attracted much interest. Here we show that, by suitably choosing the dimensions and material properties of the hybrid waveguide, a very compact and broadband TE-pass polarizer can be implemented. Finite-difference time-domain simulation indicates that the proposed device can provide large extinction ratio with low insertion loss for the TE mode.