Anshi Xu

Optical gyroscope based on a coupled resonator with the all-optical analogous property of electromagnetically induced transparency

The electromagnetically induced transparency- (EIT)-like phenomenon, called coupled-resonator-induced transparency (CRIT), could occur through a classical mean in a coupled resonator structure, due to classical destructive interference. We propose to utilize this property to construct a miniature highly sensitive gyroscope. We analyze the Sagnac effect in the CRIT structure and point out that the Sagnac phase shift contributed by the whole structure is notably enhanced due to its highly dispersive property. An explicit expression of the phase shift is derived and discussed. To realize the implementation of the CRIT-structure-based gyroscope, issues that ought to be considered are fully discussed here, such as the fabrication possibility, linewidth, shot-noise-limit sensitivity, and integration.

A top-emission organic light-emitting diode with a silicon anode and an Sm/Au cathode

A top-emission organic light-emitting diode (TEOLED) with a p-type silicon anode and a semitransparent samarium/gold cathode has been constructed and studied. With a structure of Al∕p-Si∕SiOx∕N,N′-bis-(1-naphthl)-diphenyl-1,1′-biphenyl-4,4′-diamine(NPB)∕Tris-(8-hydroxyquinoline)aluminum(Alq)∕LiF∕Al, we have found that compared to indium-tin-oxide, the p-Si anode enhances the unbalance between electron- and hole-injection, which is a disadvantage factor for the light-emitting efficiency of the TEOLED. Selecting p-Si wafers with suitable electric resistivities and inserting an ultrathin low temperature grown SiOx layer of about 1.5nm between the anode and NPB can effectively restrict hole-injection. Moreover, a low work function Sm∕Au cathode was used to enhance electron-injection. The electroluminescence efficiency of the TEOLED depends on the thickness of the Sm layer in the cathode. A current efficiency of 0.55cd∕A and a power efficiency of 0.07lm∕W have been reached.

Single-Sideband Modulation Based on an Injection-Locked DFB Laser in Radio-Over-Fiber Systems

We report an experimental demonstration of optical single-sideband (SSB) modulation in 60-GHz radio-over-fiber systems based on an injection-locked distributed-feedback (DFB) laser. Two heterodyning optical modes with 60-GHz spacing are injected into the DFB laser and one of them is used to lock the DFB laser. When the DFB laser is directly modulated, the modulation index of the locked mode is 15 dB larger than that of the unlocked one. The 2.5-Gb/s data transmission at 60 GHz is successfully achieved over 50-km standard single-mode fiber using the proposed SSB scheme.

A new family of 2D variable-weight optical orthogonal codes for OCDMA systems supporting multiple QoS and analysis of its performance

A new family of two-dimensional variable-weight and constant-length optical orthogonal codes (2D VWOOCs) is proposed, and the code cardinality and BER performance for the corresponding OCDMA system are analyzed in this article. It is shown that the cardinality of 2D VWOOC is larger than that of constant-weight 2D OOC and close to the upper bound in theory. In an OCDMA network, the users employing 2D VWOOC codewords with larger Hamming weight outperform the users using 2D VWOOC codewords with smaller Hamming weight in bit-error-rate performance. Therefore, the OCDMA network employing 2D VWOOC can support diverse quality-of-services (QoS) classes and multimedia services, and make the better use of bandwidth resources in optical networks.

Interference and horizontal Fabry-Perot resonance on extraordinary transmission through a metallic nanoslit surrounded by grooves.

The debate on the underlying physics of the extraordinary optical transmission (EOT) through a metallic nano-slit surrounded with periodic grooves is largely resolved. We clarify that the EOT originates from the interference between the slit modes excited by the incident light and by the groove-generated surface plasmon polaritons modulated by the horizontal Fabry-Perot resonance effect due to the surrounding grooves. The quantitative model derived will greatly simplify the design of such structures.

Theory of the scattering of light and surface plasmon polaritons by finite-size subwavelength metallic defects via field decomposition

A theoretical model is presented for the scattering of light and surface plasmon polaritons (SPPs) by finite-size subwavelength metallic defects. Based on the decomposition of the scattered fields into SPPs and quasi-cylindrical waves (CWs), an SPP–CW model is developed to depict the multiple scattering of SPPs and CWs in finite-size defects using the elementary scattering processes in a single one. The involved elementary scattering of the CW, as well as the CW-related coefficients, which are difficult or even impossible to define and calculate according to classical scattering theory, is clarified. A close relationship between the scattering coefficients of the SPP and those of the CW has been pointed out and used to simplify the developed model. Compared to the corresponding pure SPP model and the fully vectorial computational data, the SPP–CW model is shown to be versatile and quantitatively accurate for finite-size defects such as grooves, ridges, slits or even hybrid systems of various geometrical parameters, over a broad spectral range from the visible to the thermal infrared regime.

Theory of enhanced optical transmission through a metallic nano-slit surrounded with asymmetric grooves under oblique incidence

A metallic nano-slit surrounded with asymmetric grooves is proposed as the plasmonic concentrator for oblique incident light. A theoretical model based on the surface plasmon polariton (SPP) coupled-mode method is derived for the extraordinary optical transmission (EOT) through such a structure under oblique incidence. The model is quantitatively validated with the finite element method. With the model, the physical insight of the EOT is then interpreted, i.e., the major contributions to the transmission include the vertical Fabry-Perot resonance of the slit, and the interference among slit modes excited by the incident light, by SPPs generated from groove arrays and their first-order reflections. This is quite different from the EOT through a nano-slit surrounded with symmetric grooves under normal incidence.

Analysis of the

A metal-clad optical polarizer with a resonant buffer layer has been investigated by the finite-element method in this paper. Important waveguide design parameters, such as the refractive index, thickness, interaction length, fabrication tolerance, and band-stop characteristics, have been analyzed in detail. Mode coupling within the polarizer and the losses due to coupling between the polarizer and the input and output waveguides are considered using the normal mode analysis. The loss behaviors of and modes are explained and the roles of the resonant buffer layer are interpreted. By using ultralow index layers, resonance, as well as its phase-matching conditions and excellent performance, has also been presented and discussed for this structure for the first time. Simulations show that high performance can be achieved in a wide range of the cladding thicknesses (ges 2 mum) and interaction length for both TE-pass and TM-pass polarizers. With optimized parameters under 3-mm length, it is possible to obtain a broadband TE-pass polarizer with an extinction ratio of more than 40 dB and insertion loss below 0.2 dB over 200 nm, and a TM-pass polarizer with an extinction ratio of more than 30 dB and insertion loss below 0.4 dB over 28 nm.

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We propose and numerically investigate a plasmonic triple-wavelength demultiplexing structure based on metal-insulator-metal waveguides with side-coupled nanodisk cavities. The structure consists of three output channels, each of which is sandwiched by two nanodisk cavities and functions as a dual stop-band filter. The operation principle and transmission characteristics are analyzed by using the temporal coupled-mode theory and the finite-difference time-domain method. Simulation results show that the demultiplexed wavelength of each channel can be effectively tuned by adjusting the geometrical parameters of the structure. The proposed structure will find potential applications in photonic-integrated circuits and ultracompact optical communication systems.

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A compact bidirectional polarization splitting antenna (BPSA) composed of a patterned metallic structure coated by a thin dielectric film is proposed and theoretically investigated. Using a polarization-selective array of grooves, the backside illuminated light transmitted through the central nanoslit is split and coupled into TM- and TE-polarized modes supported by the metal-dielectric-air (MDA) configuration. The operation principle of the structure is clarified and theoretically illustrated by utilizing the fully vectorial aperiodic Fourier modal method (a-FMM). Numerical simulations show that insertion losses (ILs) less than 4 dB, polarization extinction ratios (PERs) better than 18 dB, and crosstalk (CR) less than -18 dB are achieved for both polarizations in the wavelength range 1510-1570 nm. The structure will find potential applications in highly integrated polarization diversity systems and photonic integrated circuit.