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Designs and simulations of silicon-based microphotonic devices
KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The characteristics of a silicon-on-insulator (SOI) rib waveguide, including the bending loss of a multimode bent waveguide and the birefringence of a rib waveguide, are analyzed by using a finite-difference method (FDM). Based on a detailed analysis for a multimode bent waveguide, an appropriately designed multimode bent waveguide for reducing effectively the bending loss of the fundamental mode is realized. The slab height and the rib width of an SOI rib waveguide are normalized with the total height of the silicon layer and a general relation between these two normalized parameters for a nonbirefringent SOI rib waveguide is established. Using this general relation, one can easily design a nonbirefringent SOI rib waveguide. The issue of multimode effect in the SOI-based microphotonic devices such as arrayed-waveguide gratings (AWGs), etched diffraction gratings (EDGs), and multimode interference (MMI) couplers is discussed in detail. Two kinds of taper structures are proposed for reducing the multimode effects in EDGs or MMI couplers. A bi-level taper is introduced to eliminate effectively the multimode effects in an EDG or an MMI coupler. The bi-level taper is very appropriate for an EDG demultiplexer since the Si layer is etched through simultaneously for both the grating and the bottom taper structure, and thus no additional fabrication process is required. For the simulation of an AWG demultiplexer, a fast simulation method based on the Gaussian approximation is proposed and two kinds of effective and accurate three-dimensional (3D) simulation modeling are developed. The first 3D model is based on Kirchhoff-Huygens diffraction formula. To improve the computational speed, the 3D model is reduced to a two-dimensional (2D) one by integrating the corresponding field distributions in the AWG demultiplexer along the vertical direction under an assumption that the power coupled to the higher order modes in the free propagation region (FPR) is negligibly small. The equivalent 2D model has an almost the same accuracy as the original 3D model. Furthermore, a reciprocity theory is introduced for the optimal designof a special structure used for flattening the spectral response of an AWG demultiplexer. In the second 3D simulation method, we combine a beam propagation method (BPM) and the Kirchhoff-Huygens diffraction formula. In this method, a 3D BPM in a polar coordinate system is used for calculating the light propagation in the region connecting the first FPR and the arrayed waveguides, and thus the coupling coefficient of each arrayed waveguide is calculated conveniently and accurately. In the simulation of the second FPR, due to the uniform arrangement of arrayed waveguides, only several arrayed waveguides are needed in the BPM window and thus the computational efficiency is improved.

Place, publisher, year, edition, pages
Stockholm: KTH , 2005. , 61 p.
Series
TRITA-TET/DA, ISSN 0349-7836 ; 2005:01
Keyword [en]
Electronics, waveguide, silicon-on-insulator (SOI), arrayed waveguide grating (AWG)
Keyword [sv]
Elektronik
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:kth:diva-226ISBN: 91-7178-076-9 (print)OAI: oai:DiVA.org:kth-226DiVA: diva2:7967
Public defence
2005-06-03, sal E3, Osquars backe 14, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
QC 20101004Available from: 2005-05-27 Created: 2005-05-27 Last updated: 2010-10-04Bibliographically approved
List of papers
1. Analysis of characteristics of bent rib waveguides
Open this publication in new window or tab >>Analysis of characteristics of bent rib waveguides
2004 (English)In: Journal of the Optical Society of America A, ISSN 0740-3232, Vol. 21, no 1, 113-121 p.Article in journal (Refereed) Published
Abstract [en]

With a perfectly matched layer boundary treatment, a semivectorial finite-difference method is used to calculate the eigenmodes of a single-mode (SM) or multimode (MM) bent rib waveguide. A detailed analysis is given for the dependence of the bending losses (including the pure bending loss and the transition loss) on geometrical parameters of the bent rib waveguide such as the rib width, the rib height, and the bending radius. The characteristics of the higher-order modes are analyzed. It is shown that the bending loss of the fundamental mode can be reduced effectively by increasing the width and height of the rib. For an integrated device, undesired effects due to the higher-order modes of a MM bent waveguide can be removed by appropriate choice of the geometrical parameters. An appropriately designed MM bent waveguide is used to reduce effectively the bending loss of the fundamental mode, and a low-loss SM propagation in a MM bent waveguide is realized when the bending losses of the higher-order modes are large enough.

Keyword
Boundary conditions, Calculations, Eigenvalues and eigenfunctions, Finite difference method, Integrated optics, Multimode fibers, Wave equations
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-10697 (URN)10.1364/JOSAA.21.000113 (DOI)000187880400012 ()2-s2.0-0346504051 (Scopus ID)
Note
QC 20100830Available from: 2009-07-06 Created: 2009-07-06 Last updated: 2017-12-13Bibliographically approved
2. Analysis of the birefringence of a silicon-on-insulator rib waveguide
Open this publication in new window or tab >>Analysis of the birefringence of a silicon-on-insulator rib waveguide
2004 (English)In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 43, no 5, 1156-1161 p.Article in journal (Refereed) Published
Abstract [en]

A detailed analysis of the polarization characteristics (birefringence) of a silicon-on-insulator (SOI) rib waveguide is given. The fundamental TE- and TM-polarized modes of the SOI rib waveguide are calculated by a semivectorial finite-difference method. The rib width and the slab height of the SOI rib waveguide are normalized with respect to the total height of the silicon layer. A general relation between the two normalized parameters for a nonbirefringent SOI rib waveguide is obtained. According to this relation a nonbirefringent SOI rib waveguide can easily be designed. The fabrication tolerance for a nonbirefringent SOI rib waveguide is also analyzed, revealing that the tolerance can be increased by use of a larger total height of the silicon layer.

Keyword
Rib waveguides, Single-mode fibres (SMF), Birefringence, CMOS integrated circuits, Finite difference method, Light polarization, Mathematical models, Optical fibers, Refractive index, Semiconducting films, Silicon on insulator technology
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-5158 (URN)10.1364/AO.43.001156 (DOI)000188878900019 ()2-s2.0-1442331576 (Scopus ID)
Note
QC 20101004Available from: 2005-05-27 Created: 2005-05-27 Last updated: 2017-12-04Bibliographically approved
3. Reduction of multimode effects in an SOI-based etched diffraction grating demultiplexer
Open this publication in new window or tab >>Reduction of multimode effects in an SOI-based etched diffraction grating demultiplexer
2005 (English)In: Optics Communications, ISSN 0030-4018, E-ISSN 1873-0310, Vol. 247, no 4-6, 281-290 p.Article in journal (Refereed) Published
Abstract [en]

Multimode effects in the free propagation region (FPR) of a silicon-on-insulator (SOI)-based etched diffraction grating (EDG) demultiplexer are analyzed. In a conventional design, the power coupled to the higher order modes is considerable, which introduces a significant excess loss and crosstalk. It is shown that the multimode effects in an SOI EDG demultiplexer are much more detrimental than in an arrayed waveguide grating demultiplexer. Several methods for reducing the multimode effects are discussed. In particular, a laterally tapered structure between the FPR and the input/output waveguides is proposed as a simple and effective method for reducing the power coupled to the higher order modes and consequently reducing the multimode effects. The taper width is optimized to minimize the crosstalk.

Keyword
multimode effect, taper, silicon-on-insulator, etched diffraction grating, insertion loss, crosstalk, demultiplexer
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-5159 (URN)10.1016/j.optcom.2004.11.080 (DOI)000228112800006 ()
Note
QC 20100928Available from: 2005-05-27 Created: 2005-05-27 Last updated: 2017-12-04Bibliographically approved
4. Elimination of multimode effects in a silicon-on-insulator etched diffraction grating demultiplexer with bi-level taper structure
Open this publication in new window or tab >>Elimination of multimode effects in a silicon-on-insulator etched diffraction grating demultiplexer with bi-level taper structure
2005 (English)In: IEEE Journal of Selected Topics in Quantum Electronics, ISSN 1077-260X, E-ISSN 1558-4542, Vol. 11, no 2, 439-443 p.Article in journal (Refereed) Published
Abstract [en]

 Multimode effects in the free propagation region (FPR) of an etched diffraction grating (EDG) demultiplexer based on silicon-on-insulator are analyzed. The insertion loss and the crosstalk increase due to these undesired multimode effects. A bi-level taper structure between the FPR and the input/output waveguides is proposed. It is shown that such a taper structure can reduce the multimode effects to an almost negligible level. At the same time, the 3-dB passband width is enlarged by increasing the rib width. No additional fabrication process is needed for an EDG with such a design.

Keyword
air slot, crosstalk, etched diffraction grating (EDG), insertion loss, multimode effect, silicon-on-insulator (SOI), taper
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-5160 (URN)10.1109/JSTQE.2005.846543 (DOI)000228938900019 ()2-s2.0-18844371558 (Scopus ID)
Note
QC 20100913Available from: 2005-05-27 Created: 2005-05-27 Last updated: 2017-12-04Bibliographically approved
5. Compact silicon-on-insulator-based multimode interference coupler with bilevel taper structures
Open this publication in new window or tab >>Compact silicon-on-insulator-based multimode interference coupler with bilevel taper structures
2005 (English)In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 44, no 24, 5036-5041 p.Article in journal (Refereed) Published
Abstract [en]

A novel compact silicon-on-insulator- (SOI-)based multimode interference (MMI) coupler with bilevel taper structures was designed. The MMI section and the S-bend sections of the input-output waveguides are deeply etched. The input-output waveguides connecting to single-mode fibers or other photonic light circuits are etched shallowly to yield single-mode operation. A bilevel taper is introduced in the transition region between the shallowly and deeply etched regions. It is predicted theoretically that this design will not only improve the quality of the self-imaging in the MMI section but will also make the structure compact. Both the excess loss and the nonuniformity of the MMI coupler are reduced. By use of a three-dimensional beam propagation method, the performance of a 1 × 4 MMI coupler based on a SOI is simulated as a numerical example of the novel design. The simulated nonuniformity and the excess loss are approximately 0.0285 and 0.2 dB, respectively.

Keyword
Input-output waveguides, Multimode interference coupler, Self-imaging, Three-dimensional beam propagation
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-5161 (URN)10.1364/AO.44.005036 (DOI)000231292500005 ()2-s2.0-25444495247 (Scopus ID)
Note
QC 20100903. Uppdaterad från Accepted till Published (20100903)Available from: 2005-05-27 Created: 2005-05-27 Last updated: 2017-12-04Bibliographically approved
6. Optimal design for a flat-top AWG demultiplexer by using a fast calculation method based on a Gaussian beam approximation
Open this publication in new window or tab >>Optimal design for a flat-top AWG demultiplexer by using a fast calculation method based on a Gaussian beam approximation
Show others...
2006 (English)In: Optics Communications, ISSN 0030-4018, E-ISSN 1873-0310, Vol. 262, no 2, 175-179 p.Article in journal (Refereed) Published
Abstract [en]

Passband broadening of an AWG (array waveguide grating) demultiplexer with an MMI (multimode interference) coupler connected at the end of a tapered input waveguide is considered. An explicit formula based on the field propagation of an approximate Hermit-Gaussian beam is used to calculate quickly and reliably the spectral response of the AWG demultiplexer. The widths of the input waveguide, the output waveguides and the MMI coupler are optimized. The optimal design is verified with the experimental measurement.

Keyword
Arrayed waveguide grating, Flat top, Gaussian beam, MMI
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-5162 (URN)10.1016/j.optcom.2005.12.075 (DOI)000238010000007 ()2-s2.0-33646712135 (Scopus ID)
Note
QC 20100927. Uppdaterad från Submitted till Published (20100927).Available from: 2005-05-27 Created: 2005-05-27 Last updated: 2017-12-04Bibliographically approved
7. Accurate two-dimensional model of an arrayed-waveguide grating demultiplexer and optimal design based on the reciprocity theory
Open this publication in new window or tab >>Accurate two-dimensional model of an arrayed-waveguide grating demultiplexer and optimal design based on the reciprocity theory
2004 (English)In: Journal of the Optical Society of America A: Optics and Image Science, and Vision, ISSN 1084-7529, Vol. 21, no 12, 2392-2398 p.Article in journal (Refereed) Published
Abstract [en]

An accurate two-dimensional (2D) model is introduced for the simulation of an arrayed-waveguide grating (AWG) demultiplexer by integrating the field distribution along the vertical direction. The equivalent 2D model has almost the same accuracy as the original three-dimensional model and is more accurate for the AWG considered here than the conventional 2D model based on the effective-index method. To further improve the computational efficiency, the reciprocity theory is applied to the optimal design of a flat-top AWG demultiplexer with a special input structure.

Keyword
Computational complexity, Demultiplexing, Diffraction gratings, Light propagation, Light transmission, Mathematical models, Optical communication equipment, Optical design, Optimization, Two dimensional, Arrayed waveguide grating (AWG), Computational efficiency, Demultiplexer, Effective index method, Optimal design, Reciprocity theory
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-5163 (URN)10.1364/JOSAA.21.002392 (DOI)000225378200017 ()2-s2.0-10944256033 (Scopus ID)
Note
QC 20101004Available from: 2005-05-27 Created: 2005-05-27 Last updated: 2013-11-19Bibliographically approved
8. Three-dimensional hybrid modeling based on a beam propagation method and a diffraction formula for an AWG demultiplexer
Open this publication in new window or tab >>Three-dimensional hybrid modeling based on a beam propagation method and a diffraction formula for an AWG demultiplexer
2007 (English)In: Optics Communications, ISSN 0030-4018, E-ISSN 1873-0310, Vol. 270, no 2, 195-202 p.Article in journal (Refereed) Published
Abstract [en]

An efficient and accurate three-dimensional (3D) hybrid modeling, which combines a 3D beam propagation method (BPM) and the two-dimensional (2D) Kirchhoff-Huygens diffraction formula, is developed to simulate the field propagation in an arrayed waveguide grating (AWG) dernultiplexer. The 2D Kirchhoff-Huygens diffraction formula is used for the simulation of the light propagation in the free propagation regions (FPRs). A 3D BPM in a polar coordinate system is used to simulate the light propagation in the transition region between the input FPR and the arrayed waveguides so that the coupling coefficients for the arrayed waveguides are calculated conveniently and accurately. For the simulation in the transition region between the arrayed waveguides and the output FPR, only the central arrayed waveguide and several adjacent ones are needed in the computational window of a standard BPM and thus the computation efficiency is improved. Finally, a flat-top AWG is designed and fabricated to verify the reliability of the present simulation method. The calculated and measured spectral responses are in a good agreement.

Keyword
arrayed waveguide grating, hybrid method, Kirchhoff-Huygens diffraction, beam propagation method, polar coordinate, flat-top, optimal-design, star couplers, guide
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-16377 (URN)10.1016/j.optcom.2006.08.051 (DOI)000244157700014 ()2-s2.0-33845657440 (Scopus ID)
Note
QC 20100525. Tidigare titel: Three-dimensional hybrid method for efficient and accurate simulation of AWG demultiplexersAvailable from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved

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Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
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  • de-DE
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  • en-US
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  • nn-NB
  • sv-SE
  • Other locale
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  • asciidoc
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