The effect of the Kerr nonlinearity on the transmission through the nanoslit gold film

This paper has made a theoretical study of enhanced transmission through a gold grating with arrays of subwavelength slits filled with nonlinear Kerr medium. The results of the research are based on rigorous finite-difference time domain calculations. The resonance transmission peaks in the investigated wavelength range are produced as a result of the surface plasmon resonance collaborated with the localized waveguide resonance. The paper also gives a detailed analysis of the influence exerted by various fa...     

Crosstalk reduced and low power consumption polymeric thermo-optic switch

A new polymeric 1 × 2 thermo-optic switch with significantly low crosstalk and low power consumption is presented. The thermo-optic coefficients of the core layer and the cladding layer are obviously different to each other. The refractive index of the core changes so that it would be less than that of the top cladding when the temperature is sufficiently high. Using this phenomenon, low crosstalk performance is achieved. The result indicated that the crosstalk of the proposed device could be improved from −20 to −60 dB. The switching insertion loss is 1.71 dB and the total heating power is no more than 16 mW.     

Wideband and low dispersion slow light in slotted photonic crystal waveguide

We present a procedure to generate wideband and low dispersion slow light in slotted photonic crystal waveguide. By shifting the first and second rows of air holes of slotted photonic crystal waveguide, the bandwidth of slow light can be increased, with small group velocity dispersion. Using 2D plane wave expansion method, we numerically demonstrate slow light with the nearly constant group indices of 23, 42, and 54 over 17.6 nm, 6.7 nm and 3.3 nm bandwidth, respectively. The maximal normalized delay-bandwidth product is 0.26. From the fabrication's point of review, shifting the position of holes is easier to be controlled technically than changing the diameters of air holes. In addition, our simulations suggest this design is tolerant to deviation for positions of the first two rows of air holes. Therefore, the proposed approach decreases the dependence on the fabrication accuracy.     

Temperature dependence of symmetric and asymmetric structured Au stripe waveguides

The thermal effects on pigtailed 22-nm-thick, 5-μm-wide and 1-cm-long Au stripe long-range surface plasmon polariton (LRSPP) waveguides, embedded in polymer/polymer layers and in polymer/silica layers, are theoretically and experimentally demonstrated. The polymer and silica cladding layers have thermo-optic coefficients of opposite signs. As the temperature varies the Au stripe LRSPP waveguide embedded in the polymer/polymer layers retains its symmetry in the refractive index, but that embedded in the polymer/silica layers becomes asymmetric in the refractive index. The thermal sensitivity in the optical output power of the symmetric structure is smaller than 0.02 dB/°C but the sensitivity of the asymmetric structure is ∼ 0.3 dB/°C. These structures open up potential applications of the LRSPP waveguides for temperature independent/dependent photonic devices.     

Efficient weak-light amplification through phase control in a quantum well waveguide with electron spin coherence

We propose and analyze a new scheme to realize efficient weak-light amplification via phase control in a GaAs quantum well (QW) waveguide when driven coherently by two orthogonally polarized optical fields (a σ-polarized probe field and a π-polarized control field). It is shown that the amplification and absorption properties of the system are very sensitive to the relative phase between these driving fields. By choosing the relative phase appropriately, the enhanced amplification of the weak σ-polarized radiated field can be achieved in such a QW waveguide. We support our results by numerical calculation and analytical explanation. These theoretical investigations may find applications in devising the QW waveguide amplifier at room temperature.     

Laser generation of surface acoustic modes guided by copper lines of sub-micron width on silicon

Surface acoustic waves guided by a copper line embedded in a silica film on a silicon wafer were generated and detected optically using the laser-induced transient grating technique. Lines as narrow as ∼0.2 μm yield a good signal despite the much larger size of the laser spot. The phase velocity of the guided mode is slightly lower than the surface acoustic wave velocity in the thin film structure. Good correlation between the acoustic frequency and the electrical resistivity of the copper lines results from the dependence of both measurements on the line width.     

Modeling of circular integrated optical microresonators by 2-D frequency domain coupled mode theory

Circular integrated optical (ring or disk) microresonators are increasingly employed as compact and versatile wavelength filters. In this paper, we investigate a 2-D frequency domain model for these devices, based on spatial coupled mode theory. The microresonators are functionally represented in terms of two couplers with appropriate connections using bent and straight waveguides. The abstract scattering matrices of the couplers and the propagation constants of the cavity bends allow to compute the spectral responses of the resonators. Capitalizing on the availability of rigorous analytical modal solutions for bent waveguides, the constituent bent-straight waveguide couplers are modeled using a spatial coupled mode formalism derived by means of a variational principle. The resulting scattering matrices show reciprocity properties as expected according to the symmetry of the coupler structures. We present results for the spectral response and field examples for microresonators with mono- and multi-modal cavities for TE and TM polarizations. Comparisons with finite difference time domain simulations show very good overall agreement.     

基于传输线的特异材料

特异材料（metamaterials）是指自然界中不存在的具有奇异电磁特性的人工结构，通常指的是介电常数和磁导率同时为负值的左手材料（left-handed materials）。自从2002年利用传输线制备左手材料的思想被提出后，人们对基于传输线的特异材料进行了大量的研究。文章着重概述了近年来人们所提出的几种典型的传输线特异材料的结构、制备方法、实现左手性的原理以及各自的特点。     

Beam Steering Type of 1 : 4 Optical Switch Using Thermo-Optic Effect

We propose a beam steering type optical switch employing a phase shifter. It consists of collimating waveguide mirrors, an arrayed-waveguide which has deep trenches incorporating polymer materials, and input/output waveguides. The incident light is guided to the front mirror, where it is then collimated, and input to the arrayed waveguide. The number of trenches filled with polymer linearly increases in order. The refractive index of the polymer can be controlled with temperature, and the propagation direction of the output light from the arrayed waveguide can also be controlled. A switch with 15 waveguides in the array has been fabricated. The chip size is about 2:5 × 9:0 mm², the insertion loss is 10 dB, and the extinction ratio is about 10–13 dB.     

采用四根单模光纤束实现消逝波原子(或分子)波导的理论分析

提出了一种利用四根亚微米单模光纤束实现冷原子(或冷分子)波导的新方案，计算了四光纤束内空心区域的消逝波光场及其光学囚禁势.研究表明这种蓝失谐的空心消逝波光场同样可用于实现冷原子(或冷分子)的激光波导，而且与传统的中空光纤原子波导方案相比，不仅简单方便，造价低廉，而且更容易实现冷原子物质波的高效单模波导. 关键词： 单模光纤 消逝波 原子(或分子)波导