1,720,975 research outputs found
Polarization-independent polymer waveguide modulator incorporating twisted optic-axis waveguide polarization converter
No full textSIMULATION OF POLARIZATION CONVERTER FORMED BY POLING-INDUCED POLYMER WAVE-GUIDES
No full textA polarization converter using electrooptic (EO) polymer waveguides is proposed and it is simulated by a full vectorial beam propagation method (VBPM) for anisotropic medium, First, an efficient structure of poling electrodes is proposed for the fabrication of TE-mode poling-induced waveguides in EO polymer. For given electrode structures of both TE-mode and TM-mode waveguides, poling-induced dielectric tensors are calculated by the finite-element method to provide refractive index distribution data for VBPM simulation, It is shown numerically that the poled TE and TM mode waveguides work efficiently as the corresponding polarization filters. Then, new poling electrodes are suggested to fabricate a waveguide device formed by connecting the TE and TM mode waveguides adiabatically with a slowly varying structure. This waveguide device has the optic axis slowly rotating as one moves along the propagation direction, so that it will act as polarization converter. VBPM simulation shows that the polarization of the guided mode rotates following the optic axis distribution, Polarization conversion is demonstrated successfully with high conversion efficiency and low excess loss
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Y-CUT LINBO3 DIRECTIONAL COUPLER WITH A SELF-ALIGNED ELECTRODE
No full textA 2 x 2 Y-cut LiNbO3 directional coupler switch using a self-aligned uniform DELTAbeta electrode is fabricated by the proton diffusion method. Our design method makes it possible to form the electrode without the delicate alignment of the electrode pattern mask and optical waveguide. The switching voltage is also reduced due to the enhanced electro-optic efficiency by using the self-aligned electrode. To achieve the initial cross state of the uniform DELTAbeta switch that is essential for low crosstalk, we control the proton diffusion time successively after the proton exchange. The measured crosstalk level of the directional coupler switch is -23 dB approximately -29 dB and its voltage-length product is as small as 9.6 Vmm
Polymer waveguide thermo-optic switches with - 70 dB optical crosstalk
No full textTo reduce the crosstalk of the polymer waveguide optical switches, waveguide attenuators are integrated with the switch on the same substrate. The switch and attenuator shares a single connected electrode which is controlled by a single current source. Due to the simple structure of the integrated attenuator, the device length is reduced to 10 mm so as to provide low insertion loss of 0.8 and 1.1 dB for 1300 and 1550 nm, respectively. Further radiation of the remained optical signal on the switch-off branch is induced by the integrated attenuator so that the switching crosstalk is reduced to -70 dB with an applied electrical power of 200 mW. The low crosstalk is maintained for the environmental temperature range of -10 to 55 degrees C. (c) 2005 Elsevier B.V. All rights reserved
Wavelength insensitive passive polarization converter fabricated by poled polymer waveguides
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