Digitally tunable ring laser using ladder filter and ring resonator

We propose a digitally tunable ring laser incorporating a ladder filter and a ring resonator. The widely tunable ladder filter consists of two input-output waveguides and a waveguide array, and it selects one channel from the periodic outputs of the ring resonator. With this device, the passband of the ladder filter is important in terms of obtaining stable lasing operation and it becomes narrower with increasing diffraction order. However, the free-spectral range of the filter is reduced with increasing diffraction order and this induces lasing mode instability. We therefore optimize the diffraction order of the ladder filter. The device is monolithically integrated by using the InP-InGaAsP material system. We achieved 37 channel 1000-GHz spacing digitally tunable laser operation. A promising way of improving the device performance is to use a chirped ladder filter because this filter has one dominant passband.     

Thin film bulk acoustic wave piezoelectric resonators with circular ring driving electrodes for mass sensing

We study thickness-extensional vibration frequencies and modes in a thin ZnO or AlN film on a silicon layer with a circular ring driving electrode. It is shown that the vibration tends to be trapped in the annularly electroded area and decays away from the electrode edges. The convexity of the vibration distribution near the film center can be adjusted through design, and can be made nearly uniform for mass sensor application. The theoretical analysis presented can be used to optimize the design of the device.     

Widely tunable erbium-doped fiber ring laser covering both C-bandand L-band

We demonstrate a widely tunable erbium-doped fiber (EDF) ring laser covering both the conventional wavelength band (C-band) and the long wavelength band (L-band). It features a wide tunable range, high output power, low-coherent, and depolarized output. A tunable range over 80 nm (1520-1600 nm) has been achieved by optimizing the length of the EDF and by using an intracavity fiber Fabry-Perot (FFP) filter     

A broadly tunable erbium-doped fiber ring laser: experimentationand modeling

Broad-band tunability of erbium-doped silica fiber ring lasers in the 1.48-1.62 μm wavelength band is demonstrated through modeling and experiment. Tunability over the erbium-doped fiber amplifier (EDFA) C- and L-bands is achieved with a simple laser design using a single gain medium working in deep saturation. A comprehensive numerical model based on an iterative solution of propagation rate equations and spectrally resolved Giles parameters was used to analyze the impact of various laser variables. The dependence of laser output power on total cavity loss, erbium-doped fiber length, pump power, and lasing wavelength has been investigated. The calculated laser characteristics have been found in good quantitative agreement with the experimentally obtained data. Experimental results concerning wavelength tunability, output power, and lasing wavelength repeatability/stability and spectral purity are also presented     

Substrate constructed by an array of split ring resonators for a THz planar antenna

Metamaterials are artificial materials offering unique properties which render them useful for various applications. In the present paper, we examine whether it is possible to design a split ring resonators’ (SRRs) based metamaterial substrate for enhancing the performance of planar antennas operating at THz frequencies. Initially, the radiating characteristics of a simple rectangular patch antenna over two well-known SRR substrates are studied. The yielded results are then compared to those of two novel designs of metamaterial antenna substrate with SRRs of decreasing size which are proposed to improve the antenna’s performance.     

Design of axial eddy-current couplers

This paper presents different analytical and numerical approaches devoted to the analysis and design of axial eddy-current couplers. The main part of the work regards a pure analytical procedure based on variable separation method (VSM). This methodology requires a preliminary linearization of the structure to reduce the three-dimensional (3-D) problem to a two-dimensional (2-D) one. The 2-D analytical model is compared with 2-D finite-element (FE) analysis and the comparison shows the reliability of the proposed model. The analytical procedure is then largely employed for a detailed parametric study to give useful information to the designer of eddy-current couplers. A double-sided stator with permanent magnets and single and multilayer conductive disk rotors are considered. In order to take into account 3-D effects, two different models are proposed. In the first one the VSM is coupled to a 2-D FE model; in a second model a closed analytical formula allows us to consider 3-D effects. All the models are validated with experimental results and with 3-D FE analysis.     

Surface-plasmon quantum cascade microlasers with highly deformed resonators

We report the demonstration of surface-plasmon microcylinder quantum cascade lasers with circular and deformed resonators. An improved self-alignment fabrication technique was developed that allows the use of wet etching, necessary to achieve smooth and clean surfaces, in combination with the deposition of the surface-plasmon-carrying metal layer up to the very edge of the resonator, where the optical mode is mostly located. The diameter of the microcylinders ranges from 75 to 180 /spl mu/m while their deformation coefficient /spl epsiv/ ranges from /spl epsiv/=0 to /spl epsiv/=0.32. Circular microcylinder lasers show a reduction of /spl sim/50% of the threshold current density with respect to devices with standard ridge-waveguide resonators. On the other hand, highly deformed microcylinder lasers exhibit a complex mode structure, suggesting the onset of chaotic behavior.     

Modeling and validation of high selective harmonic reduced bandpass filter using coupled resonators and defected ground structures

Recent developments in wireless communication systems demand good Band pass filter (BPF) with high quality factor and good selectivity to select the required signal from the adjacent signals. In this paper one coupled Band pass filter with centre frequency 2?GHz and 30?% Fractional Bandwidth (FBW) has been designed with rectangular split ring coupled resonators formed with conventional Microstrip transmission line. This designed BPF has been simulated with the help of MoM based IE3D electromagnetic EM simulation software. Here it is found that the proposed BPF provides second harmonic nearer to the twice of its passband centre frequency and some other few harmonics. Therefore, in this paper attention also has been given towards the suppression of harmonics with the help of Defected Ground Structures (DGS) in addition with the proposed coupled microstrip BPF. The proposed structure has been measured with Agilent vector network analyzer. There is a good agreement between simulated and measured responses.     

Optical resonators with whispering-gallery modes-part I: basics

We briefly review basic properties of dielectric whispering gallery mode resonators that are important for applications of the resonators in optics and photonics.     

Optical resonators with whispering-gallery modes-part II: applications

We review photonic applications of dielectric whispering-gallery mode (WGM) resonators-tracing the growth of the technology from experiments with levitating droplets of aerosols to ultrahigh-Q solid state crystalline and integrated on-chip microresonators.     

Short-wavelength capillary lasers with tunable spatial coherence

We present a method to continuously tune the degree of spatial coherence of a short-wavelength laser. The method is based on the optical properties of the hollow-waveguide Fabry-Perot resonators with external mirrors. The potential of the technique is demonstrated experimentally on a capillary nitrogen laser (λ=337.1 nm). The results of the work can be used for the construction of short-wavelength lasers with tunable spatial coherence     

一种新型截止频率可调的滤波器设计

从传统短截线低通滤波器的设计理论出发,推导出新型开关滤波器谐振单元的截止频率和插入损耗计算公式.以频率响应的变化规律为依据,将不同谐振单元级联通过改变并联枝节长度设计任意截止频率的低通滤波器.最后利用PIN管的开关特性,连接不同微带枝节从而改变谐振网络的枝节长度,实现不同截止频率开关滤波器的设计.在同一电路设计了截止频率分别为0.9 GHz、1.5 GHz、2 GHz三波段的低通滤波器,并对其进行了仿真、优化和加工实物测试,验证了理论分析的正确性.     

Micromachined wavelength tunable laser with an extended feedbackmodel

We present here a miniaturized wavelength tunable laser with an extended feedback model for potential all optical network applications. The feedback model has been developed to study the wavelength tuning characteristics of the micromachined tunable lasers in the weak and medium feedback limits. The miniaturized tunable laser, having a size of 2 mm × 1.5 mm × 1 mm, is an integrated Fabry-Perot diode laser with a surface micromachined mirror and a butt coupled optical fiber. A wavelength tuning range of 16 nm is achieved by moving the micromirror laterally, which is done by driving an electrostatic comb drive attached to the three-dimensional micromachined mirror     

Hybrid-mode analysis of bilateral multilayered anisotropic CPW couplers

The dispersive characteristics of multilayered bilateral anisotropic coplanar couplers are determined using the spectral domain method. The dyadicadmittance Green's function is derived for both open and shielded couplers by extending the immittance-approach technique to multilayered structures via a recursive process that takes into account the anisotropy of the material. The number of dielectric layers is arbitrary and can be chosen by the designer. Explicit algorithms and numerical results are provided that describe the propagation characteristics of these structures for both electric and magnetic wall symmetries. The convergence and CPU times are also investigated.     

Design of high-power multiplexers with interacting,synchronously tunable channels

A novel circuit configuration is presented for tunable combining multiplexers. Using reciprocal devices, the new circuit enables any channel to be tuned without the adverse effect of frequency pulling on the other channels. Experimental results in the 900 MHz band using dual-mode dielectric resonators are in close agreement with theory.     

A ring network with VLAN tag

The proposed Ring Network with VLAN Tag offers the features of wrapping/steering control functions and 1+1 path protection function, maintaining compatibility with the Ethernet media access control scheme. The key technology for “Path concept” is VLAN tag swapping operation. A set of primary and backup paths is defined between ring nodes, which are distinguished by a flag bit in VLAN tag field. On failure detection, the path is switched within the path set by the tag swapping. Tag swapping at the failure detection node, while tag swapping at the source node achieves steering operation, achieves Wrapping operation. The restoration behavior is almost the same as that of Resilient Packet Ring (RPR). Since the tag swapping control is based on hardware processing, high‐speed operation is also expected. Furthermore, because the paths are independently designed from the physical topology, the scheme can be applied to networks other than physical ring networks. The proposed scheme will fit to the path control for next‐generation Ethernet over WDM system. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 166(1): 60–66, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20422     

Rotary actuators with multipole ring magnets

Rotary actuators are electromagnetic devices developing mechanical torque with limited rotary motion. Because of their simplicity and low cost they are finding more and more applications, especially in the automotive field. This paper describes a novel homopolar rotary actuator with a ring-type radially magnetized multipolar permanent magnet featuring a high force density “transverse flux” configuration which performs a spring action by developing electromagnetic torques with limited angular movement. Because of the magnetically complicated and nonsymmetrical rotary actuator configuration, the analysis of this actuator is based on 3-D finite element software. The analysis, which is well supported by test results, shows that symmetrical magnetic forces in both directions of rotation were achieved with a stable equilibrium position, satisfying all design requirements to enhance the basic hydraulic power steering system of passenger vehicles     

Optical sensing of biomolecules using microring resonators

A biosensor application of vertically coupled glass microring resonators with Q/spl sim/12 000 is introduced. Using balanced photodetection, very high signal to noise ratios, and thus high sensitivity to refractive index changes (limit of detection of 1.8/spl times/10/sup -5/ refractive index units), are achieved. Ellipsometry and X-ray photoelectron spectroscopy results indicate successful modification of biosensor surfaces. Experimental data obtained separately for a bulk change of refractive index of the medium and for avidin-biotin binding on the ring surface are reported. Excellent repeatability and close-to-complete surface regeneration after binding are experimentally demonstrated.     

多路并行可调谐能量采集电路的设计与实现

针对传统能量采集器输出功率过低、单一能量采集单元不足以直接驱动传感器节点等负载的问题,设计了一种多路并行可调谐能量采集电路。该电路包括能量采集源模块、全桥整流模块、电容存储模块、电压调整模块和负载模块五部分。Multisim软件仿真结果表明该电路的最终输出电压相比标准能量采集(standard energy harvesting,SEH)电路提高了1.11倍;实验测试结果显示,采用该电路后输出电压稳定在5 V,最大输出功率为15 m W,比SEH电路提高2.12倍,能量传输与利用效率显著提高。