Box-Like Response of Microring Resonator Filter by Stacked Double-Ring Geometry

Yasuo KOKUBUN  Takashi KATO  Sai Tak CHU  

Publication
IEICE TRANSACTIONS on Electronics   Vol.E85-C   No.4   pp.1018-1024
Publication Date: 2002/04/01
Online ISSN: 
DOI: 
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Issue on Recent Progress of Integrated Photonic Devices)
Category: Hybrid and Passive Devices
Keyword: 
optical filter,  optical waveguide,  ring resonator,  pass band flattening,  stacked configuration,  

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Summary: 
The Lorentzian-shape filter response of a microring resonator filter is not suitable to the practical use in WDM systems, because of the lack of pass band flatness, high cross talk, and the large wing in the stop band. Therefore, the tailoring of filter response shape is required to improve the performance. In this paper, the authors designed and demonstrated the box-like filter response of microring resonator filter by using the supermodes of stacked double microring resonators. The thicknesses of microrings and the separation between them were optimally designed to give the maximally flat response. A fine fabrication process was developed to achieve the deep and very smooth side wall. The shape factor, which is defined by the ratio of -1 dB bandwidth to -10 dB bandwidth, was successfully improved by three factors from 0.17 of Lorentzian shape to 0.51.