A photonic wire-based directional coupler based on SOI

A photonic wire-based directional coupler based on SOI was fabricated by e-beam lithography (EBL) and the inductively coupled plasma (ICP) etching method. The size of the sub-micron waveguide is 0.34 mu m x 0.34 mu m, and the length in the coupling region and the separation between the two parallel waveguides are 410 and 0.8 mu m, respectively. The measurement results are in good agreement with the results simulated by 3D finite-difference time-domain method. The transmission power from two output ports changed reciprocally with about 23 nm wavelength spacing between the coupled and direct ports. The extinction ratio of the device was between 5 and 10 dB, and the insertion loss of the device in the wavelength range 1520-1610 nm was between 22 and 24 dB, which included an about 18.4 +/- 0.4 dB coupling loss between the taper fibers and the polished sides of the device. (c) 2008 Elsevier B.V. All rights reserved.