DESIGN OF A NEW TYPE OF ELECTRO-OPTIC POLYMER WAVEGUIDE MODULATOR WITH ULTRAHIGH BANDWIDTH
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DESIGN OF A NEW TYPE OF ELECTRO-OPTIC POLYMER WAVEGUIDE MODULATOR WITH ULTRAHIGH BANDWIDTH Zilong Liu1, Jihai Yu2 and Daqing Zhu3 1
Department of Physics, Wuhan University of Technology, Wuhan 430070,Hubei, China 2 Department of Physics, Yichun University, Jiangxi, China 3 Laboratory of Integrated Photonic Devices, Institute of Laser Technology & Engineering, Huzhong University of Science & Technology, Wuhan 430074,Hubei, China Received 10 January 2006 Abstract:
In this article, rectangle, trapezoidal and T type microstrip lines
embedded into up cladding of the waveguide are designed. By the analysis of the finite element method (FEM), this embedded microstrip line has perfect velocity matching between the electric signal and lightwave carrier and at the same time, conductor loss of the trapezoidal and T type microstrip lines also reduce. Thus the modulator’s bandwidth increases greatly. Calculations show that, comparing with one of non-embedded rectangle microstrip line which is the most familiar configuration of polymer modulator, the optical 3-dB bandwidths of embedded trapezoidal and T type microstrip increase 264% and 339% respectively under the condition of impedance matching. Key
words:
Optoelectronics, Electro-Optic
Bandwidth, Polymer, Waveguide, Microstrip Line
707
Modulators,
Modulation
Liu et al.
708
1.
Introduction The electro-optic polymer modulator was given lots of interest
[1]-[7]
because of its large electro-optical (EO) coefficients, low cost, easily processing and compatibility with semiconductor materials, flexibility in molecular engineering, and so on. Comparing with the optical modulator made up of LiNbO3, relatively low permittivity (about between 2.0 and 4.0) and low dispersion in the index of refraction in going from infrared to millimeterwave frequency result in the extent of velocity mismatching between electric signal and lightwave carrier is improved. Thus the modulation bandwidth of electro-optic polymer modulator reached to high level not needing clever design of electrodes as done in design of LiNbO3 optical modulator. For instance, D. Chen et al. reported a polymer modulator with an operating frequency of 113GHz[6] in 1997. A polymer modulator with 3-dB bandwidth exceeding 150 GHz was also reported in 2002[7] by M. Lee et. al. Until now, their works still are records. At present, high-speed optical networks use bandwidths of 10 GHz (~ 10 billion bps) per channel and 40-GHz products are being introduced. The bandwidth of current electro-optic modulator made up of polymer or LiNbO3 all can satisfy this communication requirement. But optical communication system in the future are envisioned to carry real-time multimedia data and research efforts are aiming to push bandwidths to 80,100 and even 160 GHz
[7]
, these
will require modulators with more high bandwidth or speed so that the real-time multimedia information can be encoded onto a light carrier. However, because polymer modulators can easily achieve a good velocity matching between microwave and lightwave, the c
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