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International Journal of Optics
Volume 2011, Article ID 164023, 11 pages
http://dx.doi.org/10.1155/2011/164023
Review Article

A Review of Polarization Dependence Applications for Asymmetric Waveguides Vertical Couplers in Compound Semiconductor Indium Phosphide

Cavendish Laboratory, University of Cambridge, J.J. Thomson Avenue, Cambridge CB3 0HE, UK

Received 5 May 2011; Accepted 22 June 2011

Academic Editor: Vittorio M. N. Passaro

Copyright © 2011 Chee-Wei Lee. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

This paper reviews and presents a coherent approach to the design of compact vertical coupler (VC) in InP-based compound semiconductor with variable polarization dependence. As a polarization-independent (PI) coupler, the VC is shown to transfer light with more than 90% efficiency for both transverse-electric (TE) and transverse-magnetic (TM) polarizations. As a polarization-mode splitter (PMS), the VC is shown to preferentially couple TE or TM modes with a contrast ratio of up to 20 dB. We further demonstrate the single-mesa VC, which simplifies the fabrication process and potentially could improve the process yield, and its integration with a multimode interferometer (MMI). The versatility makes the VC a compact and useful input-stage device that not only maximizes input/output coupling efficiency to small active devices but also provides a degree of polarization control before the actual device.