Gallium-diffused waveguides in sapphire

The fabrication and characterization of gallium-diffused planar waveguides in sapphire are reported. Waveguides were fabricated by diffusion of 60-200-nm-thick films of gallium oxide into c -cut sapphire at 1600 degrees C for times ranging from 6 to 16 h. Near-field intensity profiles of the guided modes were measured at wavelengths from 488 to 850 nm, and the surface-index elevation was estimated to be up to (0.6+/-0.02)x10(-2) . Potential applications for low-threshold Ti:sapphire waveguide lasers and for optical integrated circuits with passive and active elements in sapphire are discussed.     

Nanowire-based devices combining light guiding and photodetection

We demonstrate bridged nanowires on a non-single-crystal substrate as a versatile fabrication approach to combine active and passive photonic functionalities on silicon platforms. Silicon nanowires are grown on vertical non-single-crystal surfaces by a vapor-liquid-solid process and bridge a microtrench obtained by etching an amorphous optical rib waveguide. A pair of phosphorous-doped polysilicon electrodes is deposited on the walls of the waveguide microtrench for seeding the nanowire synthesis and for electrical interfacing. The bridged nanowires act as photoconductors and their photoresponse to edge-illumination from waveguided light is characterized. Taking advantage of crystalline nanowire growth on non-single-crystal substrates may ultimately lead to substrate-independent integration of best-of-breed semiconductor nanodevices for applications such as photonic integrated circuits.     

A simplified process for the bus electrodes of low resistance in passive matrix OLEDs

A simplified process for the bus electrodes of low resistance in passive matrix OLEDs using cathode separators is presented. The cathode separators are patterned both in a peripheral area and in an active area so that the bus electrodes can be formed out of a cathode metal of low resistance when the cathode metal is deposited. Using this simplified process, a single and bi-layer of aluminum and copper were tried out to form the bus and cathode electrodes and the results were analyzed. This method reduces the fabrication processes and lowers the power consumption.     

Optical microfiber passive components

Optical microfiber waveguides with diameters close to the wavelength of light possess an intriguing combination of properties, such a tight modal confinement, tailorable dispersion, and high nonlinearity, which have been utilized in many passive applications. Here, the key fabrication techniques and optical properties of microfibers are introduced, followed by a discussion of the various passive microfiber devices and sensors. Applications exploiting their strong confinement are reviewed, including harmonic generation, supercontinuum sources, gratings, tips for optical trapping and intracellular sensing and subwavelength light sources, as well as devices based on large evanescent fields such as couplers, interferometers, optical manipulators, sensors, and resonators. Furthermore, the properties and practical intricacies of manufacturing various microfiber resonators are evaluated, with a focus on their applications in sensing ranging from temperature monitoring to current, pressure, refractive index and chemicals detection.     

Ultra‐low loss waveguide platform and its integration with silicon photonics

Planar waveguides with ultra‐low optical propagation loss enable a plethora of passive photonic integrated circuits, such as splitters and combiners, filters, delay lines, and components for advanced modulation formats. An overview is presented of the status of the field of ultra‐low loss waveguides and circuits, including the design, the trade‐off between bend radius and loss, and fabrication rationale. The characterization methods to accurately measure such waveguides are discussed. Some typical examples of device and circuit applications are presented. An even wider range of applications becomes possible with the integration of active devices, such as lasers, amplifiers, modulators and photodetectors, on such an ultra‐low loss waveguide platform. A summary of efforts to integrate silicon nitride and silica‐based low‐loss waveguides with silicon and III/V based photonics, either hybridly or heterogeneously, will be presented. The approach to combine these integration technologies heterogeneously on a single silicon substrate is discussed and an application example of a high‐bandwidth receiver is shown.     

Silica waveguides on silicon and their application to integrated-optic components

A marriage of optical fibre fabrication technology and LSI microfabrication technology gave birth to fibre-matched silica waveguides on silicon: thick glass layers of high-silica-content glass are deposited on silicon by flame hydrolysis, a method originally developed for fibre preform fabrication. Silica channel waveguides are then formed by photolithographic pattern definition processes followed by reactive ion etching. This high silica (HiS) technology offers the possibility of integrating a number of passive functions on a single silicon chip, as well as the possibility of the hybrid integration of both active and passive devices on silicon. This paper reviews the NTT HiS technology and its application to integrated-optic components such as optical beam splitters, optical switches, wavelength-division multi/demultiplexers and optical frequency-division multi/demultiplexers. The clear and simple waveguide structures produced by the HiS technology make it possible to design and fabricate these components with high precision and excellent reproducibility.     

Optical theorem detectors for active scatterers

We develop a new theory of the optical theorem for scalar fields in nonhomogeneous media which can be bounded or unbounded. It applies to arbitrary lossless backgrounds and quite general probing fields. The derived formulation holds for arbitrary passive scatterers, which can be dissipative, as well as for the more general class of active scatterers which are composed of a (passive) scatterer component and an active, radiating (antenna) component. The generalization of the optical theorem to active scatterers is relevant to many applications such as surveillance of active targets including certain cloaks and invisible scatterers and wireless communications. The derived theoretical framework includes the familiar real power optical theorem describing power extinction due to both dissipation and scattering as well as a novel reactive optical theorem related to the reactive power changes. The developed approach naturally leads to three optical theorem indicators or statistics which can be used to detect changes or targets in unknown complex media. The paper includes numerical simulation results that illustrate the application of the derived optical theorem results to change detection in complex and random media.     

Active and passive structural acoustic control of the smart beam

Structural noise and vibrations control can be achieved using two strategies: active - with feed-forward controller, a sensor and an actuator [1-3] or passive, by piezoelectric shunt damping [4-8], when a piezoelectric transducer will act as a sensor and an actuator. Potential applications of these structures are investigated. Two numerical (FEM) models based on the active and passive damping strategies are compared. The numerical solutions were confirmed experimentally.     

聚焦离子束研制半导体材料光子晶体

介绍了利用聚焦离子束设备在多种半导体材料上成功研制的近红外波段二维光子晶体，给出了相关微加工结果，发现微加工的尺寸和理论设计尺寸相吻合；测试了所加工的无源光子晶体光子带隙和有源光子晶体的发光谱. 实验证明聚焦离子束可以研制二维光子晶体及相关光子晶体器件. 关键词： 聚焦离子束 半导体材料 光子晶体     

Efficient dispersion tailoring by designing alternately arranged dispersion compensating fibers and fiber amplifiers to create self-similar parabolic pulses

The parabolic similariton pulse formation by alternate arrangements of passive and active dispersion compensating fibers (DCFs) is presented here. These combinations of passive and active DCFs with constant core radii and constant nonlinearities are suggested as equivalent profiles of a dispersion tailored fiber amplifier in normal dispersion regime. The dispersion tailored fibers, usually known as dispersion decreasing fibers (DDFs) in normal dispersion regime, are capable of producing linearly chirped parabolic self-similar pulses. The DDF is designed and optimized with proper choice of fiber parameters so that considerable variation of nonlinearity can be achieved, which in turn enhances the effective gain coefficient of the fiber. Inclusion of this nonlinear variation along the DDF amplifier length leads to obtain the simulated output pulses with very small misfit parameters with respect to perfect parabolic pulse at sufficiently reduced optimum length. At the same time to avoid the fabrication difficulties of the DDF, the alternately arranged passive and active DCFs are suggested as suitable alternatives of the DDF. The performances of the cascaded systems for generation of self-similar parabolic pulses are compared with that of the DDF amplifier as well as combined systems consisting of DCFs with equal gain. The results show that the proposed alternately arranged cascaded system with less pumping requirements, are efficient enough to produce similar parabolic pulses as compared to the previously designed DDF, even when considerable amount of splice loss at each joint is included.     

Ultrafast solid-state lasers

This article is intended to provide an introduction to ultrafast laser development for scientists new to the field and to provide a snapshot of the current state-of-the-art. In the first section, the main issues concerning ultrashort pulse generation are discussed and then the basic techniques of mode-locking are reviewed at a tutorial level. These include active mode-locking, passive mode-locking with real, resonant, saturable absorbers and passive mode-locking with the optical Ken effect. Emphasis is placed on practical ultrafast solid-state lasers for real-world applications.     

An all-ZnO microbolometer for infrared imaging

Microbolometers are extensively used for uncooled infrared imaging applications. These imaging units generally employ vanadium oxide or amorphous silicon as the active layer and silicon nitride as the absorber layer. However, using different materials for active and absorber layers increases the fabrication and integration complexity of the pixel structure. In order to reduce fabrication steps and therefore increase the yield and reduce the cost of the imaging arrays, a single layer can be employed both as the absorber and the active material. In this paper, we propose an all-ZnO microbolometer, where atomic layer deposition grown zinc oxide is employed both as the absorber and the active material. Optical constants of ZnO are measured and fed into finite-difference-time-domain simulations where absorption performances of microbolometers with different gap size and ZnO film thicknesses are extracted. Using the results of these optical simulations, thermal simulations are conducted using finite-element-method in order to extract the noise equivalent temperature difference (NETD) and thermal time constant values of several bolometer structures with different gap sizes, arm and film thicknesses. It is shown that the maximum performance of 171 mK can be achieved with a body thickness of 1.1 μm and arm thickness of 50 nm, while the fastest response with a time constant of 0.32 ms can be achieved with a ZnO thickness of 150 nm both in arms and body.     

Serially grafted polymer optical waveguides fabricated by light-induced self-written waveguide technique

Serially grafted polymer optical waveguides were fabricated by the light-induced self-written (LISW) waveguide technique for the first time to our knowledge. To realize functional waveguide cores by the LISW technique, transparent materials at the writing wavelength were selected. By inserting thin transparent partitions, a serial-graft structure consisting of passive and active waveguides without any misalignment was realized automatically. This technique is advantageous for its extremely easy process over conventional fabrication techniques.     

Whispering-gallery-mode microdisk lasers produced by femtosecond laser direct writing

We report in this Letter fabrication of whispering-gallery-mode microdisk lasers by femtosecond laser direct writing of dye-doped resins. Not only is well-defined disk shape upheld on an inverted cone-shaped supporter, but the disk also exhibits significant lasing actions characteristic of an abrupt increase of light output and the significant narrowing of the spectral lines when the threshold is approached. This work shows that the laser micronanofabrication technology is not only applicable to passive micro-optical components, but also it may play an important role in fabrication of active optoelectronic devices and their integrated photonic circuits.     

Z-shaped meta-atom for negative permittivity metamaterials

A printed Z-shaped electric meta-atom is presented as an alternative design to the conventional electric-LC (ELC) resonator. We propose an easy way to redesign the ELC resonator pattern to get a compact and a low cost electric resonator exhibiting a strong electric response. Our approach involves, in the effective medium regime, redressing the resonator shape to accommodate higher inductance and lead to a lower resonance frequency without being limited by fabrication tolerances. The electromagnetic behaviour of the meta-atom has been investigated through both simulations and experiments in the microwave regime. Our results show that the Z meta-atom exhibits an electric response to normally incident radiation and can be used very effectively in producing materials with negative permittivity. The proposed planar meta-atom can find various applications in high frequency passive circuits which are designed in planar technology. Moreover, the proposed structure can be scaled to much higher frequencies via appropriate lithographic scaling.     

主动声纳方程和传播损失及混响级的定义

A.Ainslie发表文章指出传统定义的被动声纳方程严格应用起来与实际情况存在一定的偏差,某些情况下会带来严重的错误。该偏差需通过接收水听器与声源处介质的特征阻抗比来校正。主动声纳方程中存在同样的问题,其与实际情况的偏差需要用接收水听器与声源处的介质特征阻抗比的平方来校正。本文给出主动声纳方程中传播损失和混响级的重新定义,并且给出相应的两种主动声纳方程,两种方程都消除了这种不期望的特征阻抗比偏差。     

MODELLING AND VIBRATION CONTROL OF BEAMS WITH PARTIALLY DEBONDED ACTIVE CONSTRAINED LAYER DAMPING PATCH

A detailed model for the beams with partially debonded active constraining damping (ACLD) treatment is presented. In this model, the transverse displacement of the constraining layer is considered to be non-identical to that of the host structure. In the perfect bonding region, the viscoelastic core is modelled to carry both peel and shear stresses, while in the debonding area, it is assumed that no peel and shear stresses be transferred between the host beam and the constraining layer. The adhesive layer between the piezoelectric sensor and the host beam is also considered in this model. In active control, the positive position feedback control is employed to control the first mode of the beam. Based on this model, the incompatibility of the transverse displacements of the active constraining layer and the host beam is investigated. The passive and active damping behaviors of the ACLD patch with different thicknesses, locations and lengths are examined. Moreover, the effects of debonding of the damping layer on both passive and active control are examined via a simulation example. The results show that the incompatibility of the transverse displacements is remarkable in the regions near the ends of the ACLD patch especially for the high order vibration modes. It is found that a thinner damping layer may lead to larger shear strain and consequently results in a larger passive and active damping. In addition to the thickness of the damping layer, its length and location are also key factors to the hybrid control. The numerical results unveil that edge debonding can lead to a reduction of both passive and active damping, and the hybrid damping may be more sensitive to the debonding of the damping layer than the passive damping.     

光电被动测距技术

光电被动测距技术主要有基于图像处理的测距法、基于角度测量的测距法、基于目标物体辐射特性和大气光谱传输特性模型的测距法以及记时法等。综述了国内外光电被动测距技术的原理、特点及应用领域。结果表明,被动测距在工业和军事应用领域具有重要的现实意义,诸如在完成各种工业或军事任务时的机器人视觉系统,基于运动分析的空间卫星跟踪系统,导弹火控系统,自动飞行器着陆与精确导航系统,军事侦察的航空或卫星照片的自动分析系统,战场的侦察系统等领域均有广泛的应用。     

Dynamical thermal effects in InGaAsP microtubes at telecom wavelengths

We report on the observation of a dynamical thermal effect in InGaAsP microtubes at telecom wavelengths. The microtubes are fabricated by releasing a strained semiconductor bilayer and are picked up by abruptly tapered optical fibers for subsequent coupling with adiabatically tapered optical fibers. As a result of absorption by InAs quantum dots embedded in the tube structure, these microtubes show dynamical thermal effects at wavelengths around 1525 nm and 1578 nm, while they are passive at longer wavelengths near 1634 nm. The photon absorption induced thermal effect is visualized by generating a pair of microbottles. The dynamical thermal effect can be avoided or exploited for passive or active applications by utilizing appropriate resonance wavelengths.