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Design and optimization of an arbitrarily segmented traveling wave electrode for an ultrahigh speed electroabsorption modulator
KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
KTH, School of Information and Communication Technology (ICT), Optics and Photonics (Closed 20120101).ORCID iD: 0000-0001-7056-4379
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2008 (English)In: Optics Communications, ISSN 0030-4018, E-ISSN 1873-0310, Vol. 281, no 20, 5177-5182 p.Article in journal (Refereed) Published
Abstract [en]

The modulation response of an arbitrarily segmented traveling wave electroabsorption modulator (TW-EAM) with a non-periodic electrode layout is analyzed with an effective approach based on the transmission line theory. An optimization method based on a genetic algorithm is used to optimize the segmented electrode with additional capacitive pads for a TW-EAM. Optimized electrode structures are given for 165 mu m-length devices under standard 50 Omega RF termination condition and 210 mu m-length devices with smaller integrated resistors. Great enhancement of performances in modulation response is achieved as compared to the periodic design reported previously. The simulation with the parameters extracted from measurement results suggests that a 3 dB-bandwidth over 100 GHz could be achieved. The eye diagram from the simulation demonstrates that such devices would be competent for a 100Gb/s optical network.

Place, publisher, year, edition, pages
2008. Vol. 281, no 20, 5177-5182 p.
Keyword [en]
Electroabsorption, Electrodes, Genetic algorithm, Optical intensity, modulation, Transmission line theory, Traveling wave (TW) devices, Waveguide modulators, optical modulators
National Category
Atom and Molecular Physics and Optics
Identifiers
URN: urn:nbn:se:kth:diva-17879DOI: 10.1016/j.optcom.2008.07.014ISI: 000259940700018Scopus ID: 2-s2.0-50449109737OAI: oai:DiVA.org:kth-17879DiVA: diva2:335924
Note

QC 20100525

Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
In thesis
1. Study on electroabsorption modulators and grating couplers for optical interconnects
Open this publication in new window or tab >>Study on electroabsorption modulators and grating couplers for optical interconnects
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Decades of efforts have pushed the replacement of electrical interconnects by optical links to the interconnects between computers, racks and circuit boards. It may be expected that optical solutions will further be used for inter-chip and intra-chip interconnects with potential benefits in bandwidth, capacity, delay, power consumption and crosstalk. Silicon integration is emerging to be the best candidate nowadays due to not only the dominant status of silicon in microelectronics but also the great advantages brought to the photonic integrated circuits (PICs). Regarding the recent breakthroughs concerning active devices on silicon substrate, the question left is no longer the feasibility of the optical interconnects based on silicon but the competitiveness of the silicon device compared with other alternatives.

This thesis focuses on the study of two key components for the optical interconnects, both especially designed and fabricated for silicon platform. One is a high speed electroabsorption modulator (EAM), realized by transferring an InP-based segmented design to the hybrid silicon evanescent platform. The purpose here is to increase the speed of the silicon PICs to over 50  Gb/s or more. The other one is a high performance grating coupler, with the purpose to improve the optical interface between the silicon PICs and the outside fiber-based communication system.

An general approach based on the transmission line analysis has been developed to evaluate the modulation response of an EAM with a lumped, traveling-wave, segmented or capacitively-loaded configuration. A genetic algorithm is used to optimize its configuration. This method has been applied to the design of the EAMs on hybrid silicon evanescent platform. Based on the comparison of various electrode design, segmented configuration is adopted for the target of a bandwidth over 40 GHz with as low as possible voltage and high extinction ratio.

In addition to the common periodic analysis, the grating coupler is analyzed by the antenna theory assisted with an improved volume-current method, where the directionality of a grating coupler can be obtained analytically. In order to improve the performance of the grating coupler, a direct way is to address its shortcoming by e.g. increasing the coupling efficiency. For this reason, a nonuniform grating coupler with apodized grooves has been developed with a coupling efficiency of 64%, nearly a double of a standard one. Another way is to add more functionalities to the grating coupler. To do this, a polarization beam splitter (PBS) based on a bidirectional grating coupler has been proposed and experimentally demonstrated. An extinction ratio of around -20 dB, as well as a maximum coupling efficiency of over 50% for both polarizations, is achieved by such a PBS with a Bragg reflector underneath.

Place, publisher, year, edition, pages
Stockholm: KTH, 2010. xii, 80 p.
Series
Trita-ICT/MAP AVH, ISSN 1653-7610
Keyword
Photonic integrated circuit, optical interconnect, transmission line, traveling-wave, electro-absorption modulator, hybrid silicon evanescent platform, grating coupler, vertical coupling scheme, optical antenna, lag effect, polarization beam splitter
National Category
Telecommunications
Research subject
SRA - ICT
Identifiers
urn:nbn:se:kth:diva-24178 (URN)
Public defence
2010-09-27, sal 438, Isafjordsgatan 39, Kista, Stockholm, Forum, KTH, 10:00 (English)
Opponent
Supervisors
Note
QC 20100906Available from: 2010-09-06 Created: 2010-08-19 Last updated: 2011-08-30Bibliographically approved

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Westergren, UrbanHe, Sailing

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Zhejiang-KTH Joint Research Center of Photonics, JORCEPOptics and Photonics (Closed 20120101)Electromagnetic EngineeringKista Photonics Research Center, KPRC
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