Papers by Keyword: Waveguide

Abstract: Here we report on fabrication of integrated-optical sensors for relative humidity and ammonia detection based on natural polysaccharide chitosan. The sensing properties of the fabricated sensor to gaseous ammonia are presented. The sensor exhibits a linear response in the range of 1-300 ppm with the response time less than 1 second. It has been shown that 1 μm-thick chitosan-based waveguide film allows highly sensitive detection of RH level.

Abstract: In this paper the possibility of using the novel polymeric photosensitive medium for the fabrication of integrated optics elements was demonstrated. The medium is based on PMMA doped by beta-diketonatoboron difluorides. Planar and strip waveguides with the attenuation losses less than 1.8 dB/cm were fabricated in the layer of the medium. The photoinduced recording of the diffraction grating with the spatial frequency up to 3000 mm^-1 and diffraction efficiency ~5% in such waveguides was demonstrated. The possibility to improve the diffraction efficiency of recorded gratings up to 51% by chemical treatment was demonstrated.

Abstract: A one-port waveguide method and related apparatus based on the multi-state techniques is descried in this paper. This method measures only the magnitude and phase information for the reflection coefficients of four-state before and after the samples under test being loaded. On the basis of such data, the complex permittivity and permeability of the samples can be simultaneous calculated by software programmed according to the related theories discussed herein. In addition, the error analysis is also discussed in this paper. The proposed method is applicable to measure magnetic and/or medium-to high-loss materials, hence it is suitable to characterize the properties of radar absorbing materials.

Abstract: The equivalent circuit model of shielding effectiveness of the cylindrical cavity with apertures against the near-field waves of electric dipole is established. The analytical formulas for approximately calculating the shielding effectiveness are given by the adjusted transmission line method. It is shown that the near-field shielding effectiveness of a cylindrical cavity with apertures is far inferior to that of far-field. The near-filed SE of the cylindrical cavity increases with the distance between the diploe and the apertured cavity, but when the distance is greater than a half wavelength of the electromagnetic disturbances, the SE tends to be saturated. In the cavity, the electric SE increased with the distance of observation points to the apertures. Results of the adjusted TLM are in good agreement with the CST simulation results.

Abstract: In the present work, we investigated the effect of sputtering power on the structural and optical properties of ZnO films by radio frequency (rf) magnetron sputtering. Atom force microscopy (AFM), X-ray diffraction (XRD) and Prism coupling method were adopted to investigate the structure and optical properties of ZnO thin films deposited by sputtering powers in the range from 100~150W. XRD and AFM results shown that ZnO films with high c-axis preferred orientation crystalline structures have been successfully deposited under higher sputtering power condition. Moreover, it was also found that the indexes refractive of the films obtained by higher sputtering power are less than that of the bulk ZnO materials, which is closer to Crystal Refractive index.

Abstract: Resonant Micro-Optic Gyro (RMOG) is a kind of optical sensors measuring angular velocity via Sagnac Effect, which yields different central resonant frequency between the clockwise (CW) and counterclockwise (CCW) light path of a ring-resonator when rotating. In this paper, Y-type branch waveguide is put forward to replace K-type coupler in RMOG to reduce the influence of splitting ratio asymmetry due to fabrication errors and temperature drift. Y-type branch waveguide based on silicon-on-silica is designed and analyzed. Simulation results show that Y-type branch waveguide performs better fabrication tolerance than K-type coupler, which reduces the nonlinear Kerr-Effect induced noise excited by power nonuniformity of the counter-propagating beams, therefore the detection sensitivity of RMOG can be improved.

Abstract: This paper presents a novel high performance W-band MEMS duplexer for digital signal transceiver applications. The design of duplexer filters follows the insertion loss method with a Chebyshev polynomial to meet the desired spectral responses. The insertion loss and return loss of the optimized duplexer are -0.3dB and -18dB respectively, while the isolation between two pass bands is -55dB. A micro-fabrication process is designed based on MEMS technology. The deep reactive ion etching (DRIE) is used for high-aspect-ratio filter cavity mold structure. Micro-electroforming, plastic embossing, and electroplating techniques are used for low-cost and high-precision mass production program for the duplexer. Fabrication error tolerance is analyzed and it is reasonable to control the shift of frequency and return loss in the range of 0.05GHz and 2dB respectively with the designed fabrication process based on MEMS technology. It proves that the proposed micromachining fabrication technique is suitable for high performance W-band waveguide filter and duplexer design in terms of stability of RF performance.

Abstract: The present research work is focused on fabricating the chalcogenide glass optical waveguides keeping in mind their application in optical communication. The propagation loss of the waveguides is also studied at three different wavelengths. The waveguides were fabricated by dry etching using ECR Plasma etching and the propagation loss is studied using Fabry-Perot technique. The waveguides having loss as low as 0.35 dB/cm at 1.3m is achieved. The technique used to fabricate waveguide is simple and cost effective.

Abstract: Ultrasonic investigation techniques are widely used in materials characterisation and non-destructive testing applications. In special cases of applications, such as investigation of properties of melted polymers, metals and hot liquids, measurements must be performed in a wide temperature range. However conventional piezoelectric transducers cannot withstand higher temperatures than the Curie temperature. Therefore in order to protect conventional ultrasonic transducers from influence of a high temperature and to avoid depolarization, measurements must be performed using special waveguides with a low thermal conductivity between the object under investigation and the ultrasonic transducer. For measurements of the material properties, such as viscoelastic properties of materials, additional shear wave transducers must be used. In this work approach how to excite both, longitudinal and shear waves using special waveguides with mode conversion, using pair of conventional ultrasonic longitudinal wave transducers is presented. In this work numerical investigation of propagation of longitudinal and shear ultrasonic waves in the waveguides with mode conversion using finite element method and CIVA software was carried out. Modelling of propagation of simultaneously generated longitudinal and shear waves using pair of longitudinal ultrasonic transducers was performed. Influence of temperature gradient to the required incidence angle of the longitudinal wave was evaluated.

Abstract: mproving of cutting process is one of the most important requirements that are expected from the machining methods in the recent years. In some machining processes, the positive effect of ultrasonic waves to improve the cutting process is used. The cutting process efficiency depends on the structure of excitation system which generates ultrasonic waves. One of the most important elements of this system is the ultrasonic waveguide. The role of waveguide is the transfer of ultrasonic vibration energy from ultrasonic transducer to the tool cutting edge interacting with the workpiece (ultrasonic assisted machining-UAM). The UAM system performance depends on well-designed ultrasonic waveguide. The most important aspects of waveguide design are a resonant frequency, amplification factor and the determination of waveguide resonant wavelength - usually integer multiple of half wavelength. The effect of geometrical parameters of stepped waveguide on dynamical properties is presented in this paper.