Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Investigation of New Concepts and Solutions for Silicon Nanophotonics
KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP. (Laboratory of Photonics and Microwave Engineering)
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Nowadays, silicon photonics is a widely studied research topic. Its high-index-contrast and compatibility with the complementary metal-oxide-semiconductor technology make it a promising platform for low cost high density integration. Several general problems have been brought up, including the lack of silicon active devices, the difficulty of light coupling, the polarization dependence, etc. This thesis aims to give new attempts to novel solutions for some of these problems. Both theoretical modeling and experimental work have been done.

Several numerical methods are reviewed first. The semi-vectorial finite-difference mode solver in cylindrical coordinate system is developed and it is mainly used for calculating the eigenmodes of the waveguide structures employed in this thesis. The finite-difference time-domain method and beam propagation method are also used to analyze the light propagation in complex structures.

The fabrication and characterization technologies are studied. The fabrication is mainly based on clean room facilities, including plasma assisted film deposition, electron beam lithography and dry etching. The vertical coupling system is mainly used for characterization in this thesis. Compared with conventional butt-coupling system, it can provide much higher coupling efficiency and larger alignment tolerance.

Two novel couplers related to silicon photonic wires are studied. In order to improve the coupling efficiency of a grating coupler, a nonuniform grating is theoretically designed to maximize the overlap between the radiated light profile and the optical fiber mode. Over 60% coupling efficiency is obtained experimentally. Another coupler facilitating the light coupling between silicon photonic wires and slot waveguides is demonstrated, both theoretically and experimentally. Almost lossless coupling is achieved in experiments.

Two approaches are studied to realize polarization insensitive devices based on silicon photonic wires. The first one is the use of a sandwich waveguide structure to eliminate the polarization dependent wavelength of a microring resonator. By optimizing the multilayer structure, we successfully eliminate the large birefringence in an ultrasmall ring resonator. Another approach is to use polarization diversity scheme. Two key components of the scheme are studied. An efficient polarization beam splitter based on a one-dimensional grating coupler is theoretically designed and experimentally demonstrated. This polarization beam splitter can also serve as an efficient light coupler between silicon-on-insulator waveguides and optical fibers. Over 50% coupling efficiency for both polarizations and -20dB extinction ratio between them are experimentally obtained. A compact polarization rotator based on silicon photonic wire is theoretically analyzed. 100% polarization conversion is achievable and the fabrication tolerance is relatively large by using a compensation method.

A novel integration platform based on nano-epitaxial lateral overgrowth technology is investigated to realize monolithic integration of III-V materials on silicon. A silica mask is used to block the threading dislocations from the InP seed layer on silicon. Technologies such as hydride vapor phase epitaxy and chemical-mechanical polishing are developed. A thin dislocation free InP layer on silicon is obtained experimentally.

Place, publisher, year, edition, pages
Stockholm: KTH , 2010. , xii, 79 p.
Series
Trita-ICT/MAP AVH, ISSN 1653-7610 ; 2010:4
Keyword [en]
Planar integrated circuit, silicon photonics, slot waveguide, finite-difference time-domain, waveguide grating coupler, ring resonator, polarization diversity scheme, polarization beam splitter, polarization rotator, hybrid silicon laser, epitaxial lateral overgrowth, chemical-mechanical polishing.
National Category
Atom and Molecular Physics and Optics
Identifiers
URN: urn:nbn:se:kth:diva-13029OAI: oai:DiVA.org:kth-13029DiVA: diva2:320332
Public defence
2010-06-11, C1, Electrum 1, Isafjordsgatan 26, Kista, 13:47 (English)
Opponent
Supervisors
Note
QC20100705Available from: 2010-05-26 Created: 2010-05-24 Last updated: 2011-08-30Bibliographically approved
List of papers
1. Highly efficient nonuniform grating coupler for silicon-on-insulator nanophotonic circuits
Open this publication in new window or tab >>Highly efficient nonuniform grating coupler for silicon-on-insulator nanophotonic circuits
Show others...
2010 (English)In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 35, no 8, 1290-1292 p.Article in journal (Refereed) Published
Abstract [en]

We present design, fabrication, and characterization of a silicon-on-insulator grating coupler of high efficiency for coupling between a silicon nanophotonic waveguide and a single mode fiber. By utilizing the lag effect of the dry etching process, a grating coupler consisting of nonuniform grooves with different widths and depths is designed and fabricated to maximize the overlapping between the upward wave and the fiber mode. The measured waveguide-to-fiber coupling efficiency of 64% (−1.9 dB) for the transverse electric polarization is achieved by the present nonuniform grating coupler directly defined on a regular silicon-on-insulator wafer.

Identifiers
urn:nbn:se:kth:diva-13073 (URN)10.1364/OL.35.001290 (DOI)000276861100059 ()2-s2.0-77954911525 (Scopus ID)
Note

QC 20100906

Available from: 2010-05-26 Created: 2010-05-26 Last updated: 2017-12-12Bibliographically approved
2. Ultracompact low-loss coupler between strip and slot waveguides
Open this publication in new window or tab >>Ultracompact low-loss coupler between strip and slot waveguides
Show others...
2009 (English)In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 34, no 10, 1498-1500 p.Article in journal (Refereed) Published
Abstract [en]

We present both theoretical and experimental results of an ultracompact waveguide coupler that is capable of highly efficient coupling of light from strip waveguides to slot waveguides, and vice versa. By optimizing the geometrical parameters, it is possible to achieve extremely low-loss coupling. A coupling efficiency of 97% has been obtained experimentally while keeping the overall size down to the range below 10 mu m. Further analysis shows that the proposed coupler has relatively high tolerance to fabrication errors and is wavelength insensitive. (C) 2009 Optical Society of America

Keyword
ring resonators, confining light, fibers
Identifiers
urn:nbn:se:kth:diva-13074 (URN)10.1364/OL.34.001498 (DOI)000267064500003 ()2-s2.0-66349112883 (Scopus ID)
Note
QC20100702Available from: 2010-07-02 Created: 2010-05-26 Last updated: 2017-12-12Bibliographically approved
3. Polarization-insensitive ultrasmall microring resonator design based on optimized Si sandwich nanowires
Open this publication in new window or tab >>Polarization-insensitive ultrasmall microring resonator design based on optimized Si sandwich nanowires
2007 (English)In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 19, no 17-20, 1580-1582 p.Article in journal (Refereed) Published
Abstract [en]

Bent Si sandwich nanowires are used and optimized to obtain an ultrasmall polarization-insensitive microring resonator (MRR). The used Si sandwich nanowire has a low refractive index layer between two Si layers with high refractive indexes. By optimizing the refractive index and thickness of the sandwiched layer, the bent Si sandwich nanowire becomes nonbirefringent theoretically. The designed nonbirefringent nanowire has a relatively good fabrication tolerance. By using such a nonbirefringent bent Si sandwich nanowire, an ultrasmall polarization-insensitive MRR is designed.

Keyword
microring resonator (MRR), polarization insensitivity, sandwich waveguide, Si nanowire, SILICON-ON-INSULATOR, WAVE-GUIDES, RING RESONATORS, PHOTONIC WIRES, COUPLERS
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-13929 (URN)10.1109/LPT.2007.903889 (DOI)000250212600097 ()
Note
QC 20100702Available from: 2010-07-02 Created: 2010-07-02 Last updated: 2017-12-12Bibliographically approved
4. Experimental demonstration of a high efficiency polarization splitter based on a one-dimensional grating with a Bragg reflector underneath
Open this publication in new window or tab >>Experimental demonstration of a high efficiency polarization splitter based on a one-dimensional grating with a Bragg reflector underneath
2010 (English)In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 22, no 21, 1568-1570 p.Article in journal (Refereed) Published
Abstract [en]

A one-dimensional grating serving both as a polarization beam splitter and a vertical coupler for silicon photonic circuits is designed, fabricated, and characterized. Bragg reflectors are employed to improve greatly the coupling efficiency. Over 50% efficiency for both polarizations are achieved experimentally, and the extinction ratio between them is also high (-20 dB).

Keyword
Bragg reflector, grating coupler, integrated optics, polarization splitter, silicon-on-insulator (SOI)
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-13930 (URN)10.1109/LPT.2010.2070792 (DOI)000283368700005 ()2-s2.0-77957733646 (Scopus ID)
Available from: 2010-07-02 Created: 2010-07-02 Last updated: 2017-12-12Bibliographically approved
5. Silicon-based photonic crystals and nanowires
Open this publication in new window or tab >>Silicon-based photonic crystals and nanowires
2008 (English)In: Photonic Crystals: Physics and Technology / [ed] Sibilia, C.; Benson, T.M.; Marciniak, M.; Szoplik, T., Springer, 2008, 149-169 p.Chapter in book (Refereed)
Abstract [en]

This Chapter highlights issues related to dense photonic integration based on silicon platform and reviews two alternatives to achieve this goal within the diffraction limit; photonic nanowires and photonic crystal waveguides. Examples of the device concepts and demonstrators, as well as the fabrication techniques for passive Si based mesostructures, are presented. Promising prospects and recent breakthroughs in heterogeneous integration of silicon with optically active materials are indicated.

Place, publisher, year, edition, pages
Springer, 2008
Keyword
Photonic crystal, nanowire waveguide, integrated optics, silicon-on-insulator
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
SRA - ICT
Identifiers
urn:nbn:se:kth:diva-13931 (URN)10.1007/978-88-470-0844-1_9 (DOI)2-s2.0-84892213111 (Scopus ID)978-354024431-8 (ISBN)
Conference
2009 Asia Communications and Photonics Conference and Exhibition, ACP 2009; Shanghai; 2 November 2009 through 6 November 2009
Note

QC 20100702

Available from: 2010-07-02 Created: 2010-07-02 Last updated: 2014-04-23Bibliographically approved
6. Ultrasmall Si-nanowire-based polarization rotator
Open this publication in new window or tab >>Ultrasmall Si-nanowire-based polarization rotator
2008 (English)In: Journal of the Optical Society of America. B, Optical physics, ISSN 0740-3224, E-ISSN 1520-8540, Vol. 25, no 5, 747-753 p.Article in journal (Refereed) Published
Abstract [en]

A polarization rotator based on asymmetrical Si nanowires is presented and optimized for high polarization rotation efficiency (almost 100%). The present polarization rotator has a very small conversion length (similar to 10 mu m) and consequently becomes very compact. The analysis of the wavelength dependence shows the present polarization rotator has a broad bandwidth (similar to 120 nm) for high conversion efficiency (> 97%). The tolerance to various fabrication errors is also numerically studied. To compensate the fabrication error, a post-compensation method is introduced by modifying the refractive index of the up-cladding. (c) 2008 Optical Society of America.

Keyword
WAVE-GUIDES, FABRICATION TOLERANCE, CONVERTER, DESIGN, COMPACT, REALIZATION, WAVELENGTH, INP
Identifiers
urn:nbn:se:kth:diva-13934 (URN)000256323200007 ()
Note
QC20100702Available from: 2010-07-02 Created: 2010-07-02 Last updated: 2017-12-12Bibliographically approved
7. InP overgrowth on SiO2 for active photonic devices on silicon
Open this publication in new window or tab >>InP overgrowth on SiO2 for active photonic devices on silicon
2010 (English)In: Proceedings of SPIE - The International Society for Optical Engineering, SPIE - International Society for Optical Engineering, 2010, Vol. 7606Conference paper, Published paper (Refereed)
Abstract [en]

ntegrationof III-V materials on silicon wafer for active photonic deviceshave previously been achieved by growing thick III-V layers ontop of silicon or by bonding the III-V stack layersonto a silicon wafer. Another way is the epitaxial lateralovergrowth (ELOG) of a thin III-V material from a seedlayer directly on the silicon wafer, which can be usedas a platform for the growth of active devices. Asa prestudy, we have investigated lateral overgrowth of InP byHydride Vapor Phase Epitaxy (HVPE) over SiO2 masks of differentthickness on InP substrates from openings in the mask. Openingswhich varied in direction, width and separation were made withE-beam lithography allowing a good dimension control even for nano-sizedopenings (down to 100 nm wide). This mimics overgrowth ofInP on top of SiO2/Si waveguides. By optimizing the growthconditions in terms of growth temperature and partial pressure ofthe source gases with respect to the opening direction, separationand width, we show that a thin (~200 nm) layerof InP with good morphology and crystalline quality can begrown laterally on top of SiO2. Due to the thingrown InP layer, amplification structures on top of it canbe well integrated with the underlying silicon waveguides. The proposedELOG technology provides a promising integration platform for hybrid InP/siliconactive devices.

Place, publisher, year, edition, pages
SPIE - International Society for Optical Engineering, 2010
Series
Proceedings of SPIE-The International Society for Optical Engineering, ISSN 0277-786X
National Category
Nano Technology Nano Technology
Identifiers
urn:nbn:se:kth:diva-13936 (URN)10.1117/12.841181 (DOI)000285576100002 ()2-s2.0-77951686688 (Scopus ID)
Conference
SPIE Photonics West 2010 Conference on Silicon Photonics V, San Francisco, CA, JAN 24-27, 2010
Note

QC 20100705

Available from: 2010-07-05 Created: 2010-07-05 Last updated: 2016-05-02Bibliographically approved

Open Access in DiVA

fulltext(3185 kB)2433 downloads
File information
File name FULLTEXT01.pdfFile size 3185 kBChecksum SHA-512
88babe710cd34f858248476e7a780da66e276d9267cf8ee98e7b6cefb7dd05a2ea6017cec79f1373f205b26f88cffca635c5a0663c28d646344098ec82a13bfe
Type fulltextMimetype application/pdf

Search in DiVA

By author/editor
Wang, Zhechao
By organisation
Microelectronics and Applied Physics, MAP
Atom and Molecular Physics and Optics

Search outside of DiVA

GoogleGoogle Scholar
Total: 2433 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

urn-nbn

Altmetric score

urn-nbn
Total: 388 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf