A Two-Waveguide Tapered Velocity Coupler for a Variable Divider of Optical Power

Masahiro GESHIRO  Toshiaki KITAMURA  Tadashi YOSHIKAWA  Shinnosuke SAWA  

IEICE TRANSACTIONS on Electronics   Vol.E79-C   No.4   pp.587-592
Publication Date: 1996/04/25
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: PAPER
Category: Electromagnetic Theory
optical power divider,  tapered velocity coupler,  LiNbO3 waveguide,  electro-optic effect,  finite difference beam propagation method,  

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A two-waveguide tapered velocity coupler is presented for a variable divider of optical beams. The coupler consists of one tapered slab waveguide in dimension and the other slab waveguide with a constant film thickness. It is assumed that the device is fabricated on a LiNbO3 substrate, with a push/pull external electric field parallel with the optic axis applied only in the film regions of the coupler. Various numerical simulations through the finite difference beam propagation analysis show that a wide range of dividing ratios from - 15 dB to 15 dB or more can be achieved with considerably small values of driving-voltage electrode-length product and that the dividing characteristics are stable over a wide range of frequencies.