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Design, fabrication and characterization of plasmonic components based on silicon nanowire platform
KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Optical interconnects based on CMOS compatible photonic integrated circuits are regarded as a promising technique to tackle the issues traditional electronics faces, such as limited bandwidth, latency, vast energy consumption and so on. In recent years, plasmonic integrated components have gained great attentions due to the properties of nano-scale confinement, which may potentially bridge the size mismatch between photonic and electronic circuits. Based on silicon nanowire platform, this thesis work studies the design, fabrication and characterization of several integrated plasmonic components, aiming to combine the benefits of Si and plasmonics.

The basic theories of surface plasmon polaritons are introduced in the beginning, where we explain the physics behind the diffraction-free confinement. Numerical methods frequently used in the thesis including finite-difference time-domain method and finite-element method are then reviewed. We summarize the device fabrication techniques such as film depositions, e-beam lithography and inductively coupled plasma etching as well as characterization methods, such as direct measurement method, butt coupling, grating coupling etc.

Fabrication results of an optically tunable silicon-on-insulator microdisk and III-V cavities in applications as light sources for future nanophotonics interconnects are briefly discussed. Afterwards we present in details the experimental demonstrations and novel design of plasmonic components.

Hybrid plasmonic waveguides and directional couplers with various splitting ratios are firstly experimentally demonstrated. The coupling length of two 170 nm wide waveguides with a separation of 140 nm is only 1.55 µm. Secondly, an ultracompact polarization beam splitter with a footprint of 2×5.1 μm2 is proposed. The device features an extinction ratio of 12 dB and an insertion loss below 1.5 dB in the entire C-band. Thirdly, we show that plasmonics offer decreased bending losses and enhanced Purcell factor for submicron bends. Novel hybrid plasmonic disk, ring and donut resonators with radii of ~ 0.5 μm and 1 μm are experimentally demonstrated for the first time. The Q-factor of disks with 0.5 μm radii are                         , corresponding to Purcell factors of . Thermal tuning is also presented. Fourthly, we propose a design of electro-optic polymer modulator based on plasmonic microring. The figure of merit characterizing modulation efficiency is 6 times better comparing with corresponding silicon slot polymer modulator. The device exhibits an insertion loss below 1 dB and a power consumption of 5 fJ/bit at 100 GHz. At last, we propose a tightly-confined waveguide and show that the radius of disk resonators based on the proposed waveguide can be shrunk below 60 nm, which may be used to pursue a strong light-matter interaction.

The presented here novel components confirm that hybrid plasmonic structures can play an important role in future inter- and intra-core computer communication systems.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2014. , xii, 76 p.
Series
TRITA-ICT/MAP AVH, ISSN 1653-7610 ; 2014:05
Keyword [en]
Planar integrated circuit, silicon photonics, plasmonics, subwavelength, directional coupler, polarization beam splitter, disk resonator, ring resonator, finite-difference time-domain, photonic crystal, electro-optic polymer, Purcell factor.
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:kth:diva-143953ISBN: 978-91-7595-060-0 (print)OAI: oai:DiVA.org:kth-143953DiVA: diva2:709896
Public defence
2014-04-25, Sal D, Forum, Isafjordsgatan 39, Kista, 10:00 (English)
Opponent
Supervisors
Funder
Swedish Research Council, VR-621-2010-4379
Note

QC 20140404

Available from: 2014-04-04 Created: 2014-04-03 Last updated: 2016-03-07Bibliographically approved
List of papers
1. Experimental demonstration of ultra-compact directional couplers based on silicon hybrid plasmonic waveguides
Open this publication in new window or tab >>Experimental demonstration of ultra-compact directional couplers based on silicon hybrid plasmonic waveguides
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2012 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 100, no 24, 241105- p.Article in journal (Refereed) Published
Abstract [en]

Hybrid plasmonic waveguides and directional couplers have been experimentally demonstrated. Using a direct measurement method, the propagation loss of a 170 nm wide waveguide is measured to be 0.08 dB/mu m at 1550 nm when the thickness of low-index region is 56 nm. Ultra-compact directional couplers based on such hybrid plasmonic waveguides are demonstrated with gaps of 140 nm, 185 nm, 235 nm, and 290 nm. The corresponding coupling lengths measured are 1.55 mu m, 2.2 mu m, 3.2 mu m, and 4.8 mu m, respectively, which are in very good agreement with the simulations. These ultra-compact devices can be potentially used in future ultra-dense photonic integrated circuits.

Keyword
Propagation, Confinement, Integration
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-98937 (URN)10.1063/1.4729018 (DOI)000305269200005 ()2-s2.0-84863300332 (Scopus ID)
Funder
Swedish Research Council, VR-621-2010-4379ICT - The Next Generation
Note

QC 20120712

Available from: 2012-07-12 Created: 2012-07-05 Last updated: 2017-12-07Bibliographically approved
2. Ultracompact polarization beam splitter based on a dielectric-hybrid plasmonic-dielectric coupler
Open this publication in new window or tab >>Ultracompact polarization beam splitter based on a dielectric-hybrid plasmonic-dielectric coupler
2012 (English)In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 37, no 16, 3372-3374 p.Article in journal (Refereed) Published
Abstract [en]

An ultracompact polarization beam splitter (PBS) based on a dielectric-hybrid plasmonic-dielectric coupler is proposed. The device utilizes the polarization-dependent nature of hybrid plasmonic waveguides. By choosing proper waveguide parameters, a 2 x 5.1 mu m(2) PBS (including S-bends) with extinction ratios over 15 dB and insertion losses below 1.5 dB in the full C-band should be achievable. The effect of fabrication errors is also investigated.

Keyword
Wave-Guide, Confinement
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-103158 (URN)10.1364/OL.37.003372 (DOI)000307956700027 ()2-s2.0-84865485160 (Scopus ID)
Funder
Swedish Research Council, VR-621-2010-4379ICT - The Next Generation
Note

QC 20121009

Available from: 2012-10-09 Created: 2012-10-04 Last updated: 2017-12-07Bibliographically approved
3. Experimental demonstration of silicon-based metallic whispering gallery mode disk resonators and their thermo-tuning
Open this publication in new window or tab >>Experimental demonstration of silicon-based metallic whispering gallery mode disk resonators and their thermo-tuning
2014 (English)In: Conference on Optical Fiber Communication, Technical Digest Series, 2014Conference paper, Published paper (Refereed)
Abstract [en]

Si-based metallic whispering gallery mode disks with 0.5 μm and 1 μm radii are theoretically analyzed and experimentally demonstrated. Estimated Purcell factor is around 127±42. Thermo-tuning of the device is also presented.

Series
Technical Digest Series, 6886892
Keyword
Disk resonator, Experimental demonstrations, Purcell factor, Si-based, Silicon-based, Whispering gallery modes
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:kth:diva-167866 (URN)10.1364/OFC.2014.Tu2E.1 (DOI)000361020300384 ()2-s2.0-84907383480 (Scopus ID)9781557529930 (ISBN)
Conference
2014 Optical Fiber Communications Conference and Exhibition, OFC 2014, 9 March 2014 through 13 March 2014, San Francisco, CA
Note

QC 20151005

Available from: 2015-06-15 Created: 2015-05-22 Last updated: 2015-10-05Bibliographically approved
4. Design and analysis of ultra-compact EO polymer modulators based on hybrid plasmonic microring resonators
Open this publication in new window or tab >>Design and analysis of ultra-compact EO polymer modulators based on hybrid plasmonic microring resonators
2013 (English)In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 21, no 17, 20041-20051 p.Article in journal (Refereed) Published
Abstract [en]

Ultra-compact EO polymer modulators based on hybrid plasmonic microring resonators are proposed, simulated and analyzed. Comparing with Si slot microring modulator, hybrid plasmonic microring modulator shows about 6-times enhancement of the figure of merit when the bending radius is around 510 nm, due to its much larger intrinsic quality factor in sub-micron radius range. Influences of the EO polymer height and Si height on the device's performance are analyzed and optimal design is given. When operating with a bias of 3.6V, the proposed device has optical modulation amplitude of 0.8 and insertion loss of about 1 dB. The estimated power consumption is about 5 fJ/bit at 100 GHz.

Keyword
Bending radius, Design and analysis, Figure of merits, Intrinsic quality factors, Microring modulator, Microring resonator, Modulation amplitudes, Optimal design
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-129455 (URN)10.1364/OE.21.020041 (DOI)000323830500059 ()2-s2.0-84883250086 (Scopus ID)
Funder
Swedish Research Council, VR-621-2010-4379
Note

QC 20131004

Available from: 2013-10-04 Created: 2013-09-30 Last updated: 2017-12-06Bibliographically approved
5. Whispering gallery mode nanodisk resonator based on layered metal-dielectric waveguide
Open this publication in new window or tab >>Whispering gallery mode nanodisk resonator based on layered metal-dielectric waveguide
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2014 (English)In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 22, no 7, 8490-8502 p.Article in journal (Refereed) Published
Abstract [en]

This paper proposes a layered metal-dielectric waveguide consisting of a stack of alternating metal and dielectric films which enables an ultracompact mode confinement. The properties of whispering gallery modes supported by disk resonators based on such waveguides are investigated for achieving a large Purcell factor. We show that by stacking three layers of 10 nm thick silver with two layers of 50 nm dielectric layers (of refractive index n) in sequence, the disk radius can be as small as 61 nm similar to lambda(0) / (7n) and the mode volume is only 0.0175 (lambda(0) / (2n))(3). When operating at 40 K, the cavity's Q-factor can be similar to 670; Purcell factor can be as large as 2.3x10(4), which is more than five times larger than that achievable in a metal-dielectric-metal disk cavity in the same condition. When more dielectric layers with smaller thicknesses are used, even more compact confinement can be achieved. For example, the radius of a cavity consisting of seven dielectric-layer waveguide can be shrunk down to lambda(0) / (13.5n), corresponding to a mode volume of 0.005 lambda(0) / (2n))(3), and Purcell factor can be enhanced to 7.3x10(4) at 40 K. The influence of parameters like thicknesses of dielectric and metal films, cavity size, and number of dielectric layers is also comprehensively studied. The proposed waveguide and nanodisk cavity provide an alternative for ultracompact light confinement, and can find applications where a strong light-matter interaction is necessary.

Keyword
Plasmonics, Waveguide, Nanodisk, Quality factors, Mode volume, Purcell factor
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-143937 (URN)10.1364/OE.22.008490 (DOI)000335898700110 ()2-s2.0-84898639769 (Scopus ID)
Funder
Swedish Research Council, VR-621-2010-4379Swedish Research Council, VR-621-2011-4526
Note

QC 20140403

Available from: 2014-04-03 Created: 2014-04-03 Last updated: 2017-12-05Bibliographically approved
6. Ultra-sharp bends based on hybrid plasmonic waveguides
Open this publication in new window or tab >>Ultra-sharp bends based on hybrid plasmonic waveguides
2014 (English)In: European Conference on Optical Communication, ECOC, 2014Conference paper, Published paper (Refereed)
Abstract [en]

To explore the potentials of hybrid plasmonics, ultrasharp 90 degree bends and resonators based on silicon waveguide and hybrid plasmonic waveguides are simulated and analyzed. Experimental demonstrations of ring and donut resonators based on hybrid plasmonics are also presented.

National Category
Communication Systems
Identifiers
urn:nbn:se:kth:diva-168765 (URN)10.1109/ECOC.2014.6964044 (DOI)2-s2.0-84915747626 (Scopus ID)
Conference
2014 European Conference on Optical Communication, ECOC 2014; Cannes; France
Projects
urn:nbn:se:kth:diva-143953
Funder
Swedish Research Council, VR-621-2010-4379
Note

QC 20150612

Available from: 2015-06-12 Created: 2015-06-09 Last updated: 2016-03-07Bibliographically approved

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