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Design, Simulation and Characterization of Some Planar Lightwave Circuits
KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
2008 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

Optical devices based on planar lightwave circuit (PLC) technology have the advantages of small size, high reliability, possibility for large scale production, and potential integration with electronics. These devices are widely employed in optical telecommunications, sensing, data storage, imaging, and signal processing. This thesis focuses on some selected PLC based devices, such as power splitters, demultiplexers, triplexers and polarization beam splitters.

First, the basic principle of the waveguides and the simulation methods for PLC devices are discussed. A novel effective index method is introduced to reduce a two-dimensional structure to a one-dimensional one, and can be implemented for arbitrarily shaped waveguides. Numerical methods, such as finite-difference mode solver, beam propagation method, finite-difference time-domain method are introduced to analysis the mode profile of the waveguides, and the propagation properties of light in PLC devices.

Multimode interference (MMI) couplers are widely used in many PLCs, such as power splitters, ring lasers, optical switches, and wavelength division multiplexers/demultiplexers. In this work, concepts for improving the self-imaging quality of MMI couplers are analyzed and new designs are proposed. A significant improvement in performance together with compact sizes were obtained with taper sections at the input/output of MMI couplers based on SOI, and deeply etched ridges in MMI couplers based on SiO2. A polarization insensitive dual wavelength demultiplexer based on sandwiched MMI waveguides was presented.

Novel devices including triplexers and polarization beam splitters were realized by using photonic crystal (PhC) structures. Two stages of directional couplers based on PhC waveguides are cascaded to form an ultracompact triplexer. The special decoupling property of the PhC waveguide based directional coupler was utilized in the design. A novel polarization beam splitter was realized by combining a MMI coupler and a PhC which works as a polarization sensitive reflector.

Finally, fabrication and optical characterization of an ultra-compact directional coupler and PhC structures in InP are presented. In a single etching step, by using the lag-effect in inductively coupled plasma reactive ion etching, a compact directional coupler (55 μm) is demonstrated. Carrier life times in PhC structures etched by chemically assisted ion beam etching were investigated, for emitter and switching applications.

Place, publisher, year, edition, pages
Stockholm: KTH , 2008. , xiv, 84 p.
Series
Trita-ICT/MAP AVH, ISSN 1653-7610 ; 2008:9
Keyword [en]
planar lightwave circuit, waveguide, coupler, multimode interference, photonic crystal waveguide, (de)multiplexer, triplexer, polarization beam splitter, dry etching, carrier life time.
National Category
Telecommunications
Identifiers
URN: urn:nbn:se:kth:diva-4760ISBN: 978-91-7178-989-1 (print)OAI: oai:DiVA.org:kth-4760DiVA: diva2:13810
Public defence
2008-06-09, sal N2, Electrum 3, Isafjordsgatan 28, Kista, Stockholm, 10:00
Opponent
Supervisors
Note
QC 20100909Available from: 2008-05-16 Created: 2008-05-16 Last updated: 2010-09-09Bibliographically approved
List of papers
1. Improved performance of a silicon-on-insulator-based multimode interference coupler by using taper structures
Open this publication in new window or tab >>Improved performance of a silicon-on-insulator-based multimode interference coupler by using taper structures
2005 (English)In: Optics Communications, ISSN 0030-4018, E-ISSN 1873-0310, Vol. 253, no 4-6, 276-282 p.Article in journal (Refereed) Published
Abstract [en]

Multimode effects in a multimode interference (MMI) coupler based on silicon-on-insulator (SOI) are analyzed. Multimode interference in the vertical direction of an SOI-based MMI device degrades the self-imaging quality. Taper structures are introduced at the junction between input/output waveguides and multimode region to suppress the excitation of the undesired vertical modes. A 1 x 4 MMI coupler of low insertion loss (0.101 dB) and small non-uniformity (0.102 dB) is designed as a numerical example.

Keyword
multimode interference, self-imaging, modal propagation analysis, silicon on insulator, tapered structure, vertical modes
National Category
Telecommunications
Identifiers
urn:nbn:se:kth:diva-15031 (URN)10.1016/j.optcom.2005.04.078 (DOI)000231779700007 ()2-s2.0-24144437464 (Scopus ID)
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
2. Deeply etched SiO2 ridge waveguide for sharp bends
Open this publication in new window or tab >>Deeply etched SiO2 ridge waveguide for sharp bends
2006 (English)In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 24, no 12, 5019-5024 p.Article in journal (Refereed) Published
Abstract [en]

A deeply etched SiO2 ridge waveguide including the buffer, core, and cladding is presented for realizing sharp bends. The present SiO2 ridge waveguide has a strong confinement at the lateral direction, while it has a weak confinement at the vertical direction. Due to the strong confinement, a sharp bend (with a very small bending radius of about 10 mu m) is obtained for an acceptable bending loss. A detailed analysis of the loss in a bent waveguide is given by using a finite-difference method. In order to reduce the transition loss, a narrow bending section with an optimal lateral offset is used. A low leakage loss is obtained by using wide straight waveguides, and linear tapers are used to connect the wide straight section and narrow bent sections.

Keyword
bending, deep etching, ridge waveguide, silicon oxide
National Category
Telecommunications
Identifiers
urn:nbn:se:kth:diva-24446 (URN)10.1109/JLT.2006.885243 (DOI)000243888600050 ()
Note
QC 20100909Available from: 2010-09-09 Created: 2010-09-09 Last updated: 2017-12-12Bibliographically approved
3. Design of a compact multimode interference coupler based on deeply-etched SiO2 ridge waveguides
Open this publication in new window or tab >>Design of a compact multimode interference coupler based on deeply-etched SiO2 ridge waveguides
2007 (English)In: Optics Communications, ISSN 0030-4018, E-ISSN 1873-0310, Vol. 271, no 2, 404-407 p.Article in journal (Refereed) Published
Abstract [en]

A compact multimode interference (MMI) coupler is realized by using deeply-etched SiO2 ridge waveguides, which have a strong confinement in the lateral direction and improve the quality of self-images in the MMI section, A 1 x 4 MMI coupler is designed as a numerical example and demonstrates good performances such as a low insertion (0.0275 dB) and small non-uniformity (0.0507 dB). The total device size of the present MMI coupler is reduced to about 1/16 of that based on SiO2 buried waveguides.

Keyword
multimode interference, coupler, silica, waveguide, deeply etched, ridge
National Category
Telecommunications
Identifiers
urn:nbn:se:kth:diva-24455 (URN)10.1016/j.optcom.2006.10.084 (DOI)000244488900016 ()2-s2.0-33846188136 (Scopus ID)
Note
QC 20100909Available from: 2010-09-09 Created: 2010-09-09 Last updated: 2017-12-12Bibliographically approved
4. A polarization-insensitive 1310/1550-nm demultiplexer based on sandwiched multimode interference waveguides
Open this publication in new window or tab >>A polarization-insensitive 1310/1550-nm demultiplexer based on sandwiched multimode interference waveguides
2007 (English)In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 19, no 21-24, 1789-1791 p.Article in journal (Refereed) Published
Abstract [en]

A polarization-insensitive dual-wavelength demultiplexer based on sandwiched multimode interference waveguides is presented. Polarization-insensitive multimode waveguides are achieved first by choosing a suitable refractive index of the SiNx middle region. The demultiplxing function is then realized by adjusting the width and length of the multimode region. Simulation results obtained from three-dimensional beam-propagation method show that the demultiplexer can work at 1310- and 1550-nm bands for both polarizations simultaneously with a low insertion loss and a broad bandwidth.

Keyword
demultiplexer, multimode interference (MMI), polarization independent, sandwiched waveguide, wavelength demultiplexer, inp, design
National Category
Telecommunications
Identifiers
urn:nbn:se:kth:diva-17166 (URN)10.1109/lpt.2007.906836 (DOI)000251701000030 ()2-s2.0-36249001160 (Scopus ID)
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
5. Novel ultracompact triplexer based on photonic crystal waveguides
Open this publication in new window or tab >>Novel ultracompact triplexer based on photonic crystal waveguides
2006 (English)In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 18, no 21-24, 2293-2295 p.Article in journal (Refereed) Published
Abstract [en]

Two stages of directional couplers based on photonic crystal waveguides Are cascaded to form an ultracompact triplexer. The directional couplers are decoupled at the wavelength of 1310 rum. The length of the coupling region in the first directional coupler is chosen to separate the other two wavelengths (i.e., 1490 and 1550 nm), and the coupling region is tapered to improve the extinction ratios. The second directional coupler separates the wavelengths of 1490 and 1310 run. For the channel of 1550 nm, an additional directional coupler is used to reduce the crosstalk from the channels of 1490 and 1310 nm. The total size of the present triplexer is only 50 mu m x 20 mu m, and the good performance is verified with finite-difference time-domain simulation.

Keyword
directional coupler, photonic crystal (PC), triplexer, waveguide, design
National Category
Telecommunications
Identifiers
urn:nbn:se:kth:diva-16236 (URN)10.1109/lpt.2006.884722 (DOI)000243173300035 ()2-s2.0-34548565135 (Scopus ID)
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
6. Design of a Polarization Insensitive Triplexer Using Directional Couplers Based on Submicron Silicon Rib Waveguides
Open this publication in new window or tab >>Design of a Polarization Insensitive Triplexer Using Directional Couplers Based on Submicron Silicon Rib Waveguides
2009 (English)In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 27, no 11, 1443-1447 p.Article in journal (Refereed) Published
Abstract [en]

An ultracompact triplexer which could be used for both polarizations is designed by utilizing directional couplers based on submicron silicon rib waveguides. First, the polarization insensitive directional couplers are realized by carefully choosing cross-sectional geometry of the waveguide. The length of the coupling region in the first directional coupler is chosen to separate the three wavelengths ( i.e., 1490 nm to one port, 1310 and 1550 nm to the other port). The second directional coupler separates the wavelengths of 1310 and 1550 nm. For the channel of 1490 nm, an additional directional coupler is used to reduce the crosstalk from the 1310 and 1550 nm channels. The total length of the present triplexer is only 400 and simulation with three-dimensional Beam Propagation Method shows good performances for both polarizations.

Keyword
Directional coupler, polarization, silicon, triplexer, waveguide, on-insulator, difference, networks
National Category
Telecommunications
Identifiers
urn:nbn:se:kth:diva-18580 (URN)10.1109/jlt.2008.2010465 (DOI)000267712900003 ()2-s2.0-67049172733 (Scopus ID)
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
7. Proposal for an ultracompact polarization-beam splitter based on a photonic-crystal-assisted multimode interference coupler
Open this publication in new window or tab >>Proposal for an ultracompact polarization-beam splitter based on a photonic-crystal-assisted multimode interference coupler
2007 (English)In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 19, no 9-12, 825-827 p.Article in journal (Refereed) Published
Abstract [en]

An ultracompact polarization-beam splitter (PBS) combining a multimode interference (MMI) coupler and some photonic crystal (PC) structures is presented. The MMI coupler is designed to collect polarized powers reflected by or transmitted through an internal PC sturcture. The simulation result shows that the designed PBS is very short (about 50 mu m), and has a low insertion loss, a high extinction ratio, and a broad bandwidth.

Keyword
multimode interference (MMI), photonic crystal (PC), planar lightwave circuit, polarization-beam splitter (PBS), heterostructure
National Category
Telecommunications
Identifiers
urn:nbn:se:kth:diva-16711 (URN)10.1109/lpt.2007.897297 (DOI)000247353100064 ()2-s2.0-34249319476 (Scopus ID)
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
8. Ultracompact directional couplers realized in InP by utilizing feature size dependent etching
Open this publication in new window or tab >>Ultracompact directional couplers realized in InP by utilizing feature size dependent etching
2008 (English)In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 33, no 17, 1927-1929 p.Article in journal (Refereed) Published
Abstract [en]

We present the design, fabrication, and measurement of an ultracompact directional coupler in InP/InGaAsP/InP. By utilizing the lag effect in the dry etching process, in one etch step, deeply etched asymmetric waveguides with a shallow groove in between are fabricated. This special property enhances the coupling efficiency for the directional coupler and thus makes the device ultracompact. We demonstrate directional couplers as short as 55 mu m, which is only 1/30th the length of the conventional design.

Keyword
silicon-on-insulator, cl-2-h-2, devices
National Category
Telecommunications
Identifiers
urn:nbn:se:kth:diva-17852 (URN)10.1364/OL.33.001927 (DOI)000259653000001 ()2-s2.0-51749105202 (Scopus ID)
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
9. Evidence for accumulated sidewall damage in dry etched photonic crystals
Open this publication in new window or tab >>Evidence for accumulated sidewall damage in dry etched photonic crystals
Show others...
2008 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118Article in journal (Other academic) Submitted
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-8378 (URN)
Note
QS 20120314Available from: 2008-05-08 Created: 2008-05-08 Last updated: 2017-12-14Bibliographically approved
10. Development of damage and its impact on surface recombination velocities in dry-etched InP-based photonic crystals
Open this publication in new window or tab >>Development of damage and its impact on surface recombination velocities in dry-etched InP-based photonic crystals
Show others...
(English)Manuscript (Other academic)
Identifiers
urn:nbn:se:kth:diva-8379 (URN)
Note
QC 20100709Available from: 2008-05-08 Created: 2008-05-08 Last updated: 2013-11-19Bibliographically approved

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