Cascading Second-Order Microring Resonators for a Box-Like Filter Response

We demonstrate an optical filter using multistage of second-order microring resonators (2nd-order MRRs) for a box-like filter response. All stages have identical structure parameters elaborately designed to obtain a flat-top spectrum. The maximally flat condition is deduced in consideration of loss...

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Bibliographic Details
Published in:	Journal of lightwave technology Vol. 35; no. 24; pp. 5347 - 5360
Main Authors:	Zhang, Lei, Zhao, Haiyang, Wang, Haoyan, Shao, Sizhu, Tian, Wenjing, Ding, Jainfeng, Fu, Xin, Yang, Lin
Format:	Journal Article
Language:	English
Published:	New York IEEE 15-12-2017 The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Subjects:	Band-pass filters Bandwidths Holes Insertion loss Optical filters Optical resonators Resonator filters Resonators Silicon photonics Wiring
Online Access:	Get full text
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Summary:	We demonstrate an optical filter using multistage of second-order microring resonators (2nd-order MRRs) for a box-like filter response. All stages have identical structure parameters elaborately designed to obtain a flat-top spectrum. The maximally flat condition is deduced in consideration of loss and compared with those reported in literature. We present the insertion loss, extinction ratio, bandwidth, and roll-off rate of the maximally flat response. We find that for the flat response of a 2nd-order MRR, the product of bandwidth and roll-off rate is constant. We compare the cascading 2nd-order MRRs with single-stage high-order filters with the same number of ring cavities. We find that the cascading structure has comparable performances in the aspects of insertion loss and roll-off rate for small radius. This cascading structure relaxes the fabrication tolerance and mitigates the difficulty of electrical wiring difficulty since there are only two ring cavities in each stage. As a proof of concept, we fabricate this kind of optical filter with ten stages on silicon-on-insulator platform, with each ring cavity tunable and each stage measurable. We obtain five flat-top responses corresponding to one to five cascading stages. The five-stage filter response has a 3 dB bandwidth of ~17 GHz, a roll-off rate of ~-5 dB/GHz at -3 dB point, and an on-chip insertion loss of ~-6 dB.
ISSN:	0733-8724 1558-2213
DOI:	10.1109/JLT.2017.2775658