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Plasma assisted technology for Si-based photonic integrated circuits
KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The last two decades have witnessed a large increase in capacity in telecommunication systems, thanks to the development of high bandwidth, fiber optic based networks. Nevertheless the continuing growth of Internet data traffic, fuelled by the development of numerous services like on-line commerce, video on demand, large audio/video files downloads, demands for a significant increase in the ability of the network nodes to manage incoming and outcoming data streams effectively and fast. The different functionalities that are needed include add/drop channel multiplexing, routing, signal reshaping and retiming, electrical/optical and optical/electrical conversion. This has stimulated a large effort towards the investigation of technologies for opto-electronic integration at a wafer level, in order to cope with all the required operations, while limiting overall costs. Among the different approaches proposed, one of the most promising is the “Silicon optical bench”, which relies on the well established VLSI technology for the microelectronics part and on planar lightwave circuits (PLCs) made either with silica-on-silicon waveguide technology (low index contrast) of amorphous silicon technology (high index contrast) on the integrated optics side.

This thesis presents the development of new techniques and methodologies utilized in photonic device fabrication, which can be used to facilitate integration of temperature sensitive elements. The process is based on low temperature, plasma assisted, thick film deposition. First, a low temperature (300°C) deposition process based on Plasma assisted Chemical Vapour Deposition (PACVD) for the fabrication of silica based Planar Lightwave Circuits (PLC) is developed. The low thermal budget lends itself to monolithic integration with devices fabricated with different technologies. Absorption bands at around the wavelengths 1.48µm and 1.51µm caused by N-H and Si-H bonds within the material, respectively, had previously been thought to be intrinsic to the PACVD deposition method, when using N2O as oxidant gas of SiH4 and the other dopant precursors. The traditional method to eliminate these absorption bands was high temperature (>1000°C) annealing that seriously hinders device integration. An important achievement in this thesis is the improved suppression of these two absorption bands while keeping the whole fabrication temperature below 300°C and also having a high deposition rate. A complete fabrication process for silica planar lightwave circuits was also developed, by optimising the photolithography and etching step. Finally the effect of dopants like Ge and B on the optical properties of the deposited silica glass was investigated, with particular emphasis to the photosensitive properties of the material upon illumination in the near UV. UV trimming is shown to be a versatile method to selectively control polarization birefringence of devices. Transmission dips of above 50dB were achieved in photo-induced gratings in low temperature deposited B-Ge codoped waveguide cores, without the need for hydrogen loading or other sensitisation techniques. The application of a high refractive index like amorphous silicon is addressed for the realization of efficient Bragg reflectors, either as vertical cavity laser mirrors or as dispersive element for planar waveguides used in highly selective co-directional coupler filters. Applications of amorphous silicon as core material for photonic crystal devices are also shown. The investigations carried out in this thesis show that PACVD technology can provide low-loss and UV sensitive material suitable for realizing a variety of low cost integrated devices for future all optical networks.

Place, publisher, year, edition, pages
Stockholm: KTH , 2005. , 34 p.
Series
Trita-MVT, ISSN 0348-4467 ; 2005:2
Keyword [en]
Electrical engineering, silica-on-silicon technology, PACVD, plasma deposition, photonic integrated circuits, planar lightwave circuits
Keyword [sv]
Elektroteknik, elektronik och fotonik
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:kth:diva-148OAI: oai:DiVA.org:kth-148DiVA: diva2:7379
Public defence
2005-03-21, Sal C1, KTH-Electrum, Isafjordsgatan 22, Kista, 10:00 (English)
Opponent
Supervisors
Note
QC 20101004Available from: 2005-03-10 Created: 2005-03-10 Last updated: 2010-10-04Bibliographically approved
List of papers
1. PECVD technology for low temperature fabrication of silica-on-silicon based channel waveguides and devices
Open this publication in new window or tab >>PECVD technology for low temperature fabrication of silica-on-silicon based channel waveguides and devices
2000 (English)In: Proceedings of SPIE, the International Society for Optical Engineering, ISSN 0277-786X, E-ISSN 1996-756X, Vol. 4087, 503-507 p.Article in journal (Refereed) Published
Abstract [en]

Silicabased planar technology on silicon has been identified as avery serious source of devices for optical communications:ystems. Low temperaturefabrication of passive and active structures is of special interestas it allows monolithicintegration with temperature sensitive semiconductor components ona common silicon platform.Standard PEC\'D (Plasma Enhanced Chemical Vapour Deposition)processing for fabrication of silica based opticalwaveguides has been investigatedto optimize the process parameters. We chose a high powerprocess regime with highratio between nitrous oxide and silane gasflows as the best conditions. Significant improvement in optical propertiesofsilica-on-silicon planar waveguides for optical communication in the 1.50 -1.55 tmwavelength range has been obtained.

National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-4993 (URN)10.1117/12.406444 (DOI)2-s2.0-84875459700 (Scopus ID)
Note

QC 20141209

Available from: 2005-03-10 Created: 2005-03-10 Last updated: 2017-12-05Bibliographically approved
2. Material consideration for integrated optics in silica-on-silicon technology
Open this publication in new window or tab >>Material consideration for integrated optics in silica-on-silicon technology
2003 (English)In: Proceedings volumes / Electrochemical society, ISSN 0161-6374, Vol. 1, 130-144 p.Article in journal (Refereed) Published
Abstract [en]

In this paper we present guidelines for optimization of process parameters for low temperature deposition of silica films for optical applications. The fabrication of optical integrated circuits based on silica deposition on silicon substrates with plasma enhanced CVD introduces different challenges in this technology, with respect to its traditional application in the field of microelectronics. The thick layers required, make deposition rate a very important parameter of merit. High accuracy of this thickness and refractive index as well as their uniformity over large area of the wafer are also very important for the functionality of the fabricated devices. Finally low processing temperature is essential as it allows monolithic integration with temperature sensitive semiconductor components. In this study a commercial parallel plate reactor has been used and the deposition parameters have been analysed to determine the process window, which allows fulfilling all these demands, so as to make a subsequent high temperature consolidation step not necessary.

National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-4994 (URN)
Note
QC 20101004Available from: 2005-03-10 Created: 2005-03-10 Last updated: 2017-12-05Bibliographically approved
3. Influence of Ge content on the optical quality of Plasma CVD deposited Silica films
Open this publication in new window or tab >>Influence of Ge content on the optical quality of Plasma CVD deposited Silica films
2002 (English)Conference paper, Published paper (Refereed)
Abstract [en]

The feasibility of a full low temperature process, based on Plasma Enhanced Chemical Vapor

Deposition, for the fabrication of low loss silica-based optical waveguides is investigated.

Results from XPS, FTIR, ERDA, isochronal wet etch rate, prism coupler measurements show

that (low frequency) RF power is a critical parameter to improve microstructural properties of

as-deposited SiO

2 and minimize Rayleigh scattering. Ge doping of the silica matrix in the

core layer increases network disorder and point defects density, mainly due to the highly

reactive characteristics of the employed gas precursor (germane) and the high sticking

coefficients of its radicals. Measurements on fabricated optical waveguides show that for

relative refractive index differences between core and cladding up to 0.75%, the optical

losses are acceptable for the fabrication of high performance devices.

National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-4995 (URN)
Conference
American Vacuum Society’s 49th International Symposium
Note

NR 20160427

Available from: 2005-03-10 Created: 2005-03-10 Last updated: 2016-04-27Bibliographically approved
4. Grating-assisted add-drop multiplexer realized in silica-on-silicon technology
Open this publication in new window or tab >>Grating-assisted add-drop multiplexer realized in silica-on-silicon technology
2003 (English)In: Proceedings of SPIE, the International Society for Optical Engineering, ISSN 0277-786X, E-ISSN 1996-756X, Vol. 4941, 43-50 p.Article in journal (Refereed) Published
Abstract [en]

Silica-on-Silicon is a well established technology for the fabrication of low insertion loss planar lightwave circuits. The Ge-doped waveguide core material, deposited with low temperature plasma enhanced chemical vapor deposition and not subjected to high temperature annealing, is highly UV light photosensitive, due to residual Ge/Si-OH groups in the material that, similarly to hydrogen loading, can contribute to the formation of those defect centers responsible for the photosensitivity. Gratings have been-fabricated using a pulsed 193 nm ArF excimer laser and a phase mask. 25 mm long gratings, written on standard straight waveguides, show a record 47 dB extinction ratio and 0.2 nm rejection bandwidth for TE polarization, without hydrogen loading. Such narrow linewidth filters could find application in dense WDM systems. We designed and fabricated a compact Add/Drop multiplexer based on a high bandwidth, 2x2 multimode interference device, having a Bragg grating written in the multi-mode region. The characterisation for the TE polarisation prove the proposed Add/Drop principle, showing, in correspondence of the dropped channel, a 30dB dip at the transmitted output and a reflection peak at the drop output, this last having a larger bandwidth, and around 3dB excess loss respect to the transmitted channels.

Keyword
add-drop multiplexing, Bragg grating, multimode interference (MMI), silica-on-silicon technology, planar lightwave circuit (PLC)
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-4996 (URN)10.1117/12.468509 (DOI)000182689900005 ()
Note
QC 20101004Available from: 2005-03-10 Created: 2005-03-10 Last updated: 2017-12-05Bibliographically approved
5. Birefringence control in plasma-enhanced chemical vapor deposition planar waveguides by ultraviolet irradiation
Open this publication in new window or tab >>Birefringence control in plasma-enhanced chemical vapor deposition planar waveguides by ultraviolet irradiation
Show others...
2000 (English)In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 39, no 24, 4296-4299 p.Article in journal (Refereed) Published
Abstract [en]

Complete birefringence compensation is demonstrated in plasma-enhanced chemical vapor deposition waveguides by 193-nm postexposure. A single relaxation process dominates the decay in stress anisotropy, indicating that compressive stress from the substrate leads to an elastic stress anisotropy at the core.

Keyword
Anisotropy, Compressive stress, Plasma enhanced chemical vapor deposition, Ultraviolet radiation
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-4997 (URN)10.1364/AO.39.004296 (DOI)000088833600013 ()
Note
QC 20100901Available from: 2005-03-10 Created: 2005-03-10 Last updated: 2017-12-05Bibliographically approved
6. Photosensitivity of boron-codoped PECVD films in application to grating assisted WDM devices
Open this publication in new window or tab >>Photosensitivity of boron-codoped PECVD films in application to grating assisted WDM devices
2004 (English)In: INTEGRATED OPTICS AND PHOTONIC INTEGRATED CIRCUITS / [ed] Righini, GC; Honkanen, S, BELLINGHAM: SPIE-INT SOC OPTICAL ENGINEERING , 2004, Vol. 5451, 191-198 p.Conference paper, Published paper (Refereed)
Abstract [en]

UV sensitivity of B-Ge codoped cores in PECVD silica waveguides has been investigated. Photoinduced refractive index changes have been introduced by KrF excimer laser irradiation at 248 rim, without any presensitization method. The effects of B codoping of Ge doped silica have been examined. It has been shown that B addition mildly increases glass network disorder, by broadening the O bridging angle distribution as from FTIR measurements, but on the other hand it does not produce point defects which may contribute to the absorption band at 5eV already generated by the presence of Ge doping. The fabricated channel waveguides show low optical loss even without high temperature annealing. Strong Bragg gratings imprinted into these waveguides confirm that in non thermally annealed Ge doped PECVD silica glass, where a small absorption band still exist at 5eV, B codoping supplies sufficient photosensitivity amplification to make hydrogen loading unnecessary.

Place, publisher, year, edition, pages
BELLINGHAM: SPIE-INT SOC OPTICAL ENGINEERING, 2004
Series
PROCEEDINGS OF THE SOCIETY OF PHOTO-OPTICAL INSTRUMENTATION ENGINEERS (SPIE), ISSN 0277-786X ; 5451
Keyword
photosensitivity, Bragg gratings, silica-on-silicon technology, planar lightwave circuit (PLC), boron codoping, PECVD fabrication
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-4998 (URN)10.1117/12.545813 (DOI)000223995500022 ()2-s2.0-12344253989 (Scopus ID)0-8194-5374-9 (ISBN)
Conference
Conference Optics and Photonic Integrated Circuits. Strasbourg, FRANCE. APR 27-29, 2004
Note
QC 20101004 QC 20111025Available from: 2005-03-10 Created: 2005-03-10 Last updated: 2011-11-01Bibliographically approved
7. Narrow band coupler based on one-dimensional Bragg reflection waveguide
Open this publication in new window or tab >>Narrow band coupler based on one-dimensional Bragg reflection waveguide
Show others...
2003 (English)In: 2003 Optical Fiber Communication Conference: Altanta, Georgia, 2003, 44-46 p.Conference paper, Published paper (Refereed)
Abstract [en]

A new configuration based on the coupling between a conventional low loss, weakly guiding channel waveguide and a Bragg reflection waveguide (BRW) was discussed. The strong difference between the dispersion of a Bragg reflection waveguide and a channel waveguide was used to create a narrow band coupler. The two-dimensional analysis of the BRW was generally based on the transfer matrix method. The structure consisted of a weakly guiding conventional Ge-doped silica waveguide on the top of which a BRW was stacked. The number of periods in the mirror between the BRW and the silica waveguide affected the coupling length and ultimately the bandwidth.

Series
Conference on Optical Fiber Communication, Technical Digest Series, 86
Keyword
Bandwidth, Electromagnetic dispersion, Light polarization, Light reflection, Light transmission, Mirrors, Plasma enhanced chemical vapor deposition, Refractive index, Silica, Wavelength division multiplexing, Band couplers, Bragg reflection waveguides (BRW)
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-10698 (URN)10.1109/OFC.2003.1247478 (DOI)1-55752-746-6 (ISBN)
Note
QC 20101004Available from: 2009-07-06 Created: 2009-07-06 Last updated: 2010-10-04Bibliographically approved
8. Directional coupler wavelength selective filter based on dispersive  Bragg Reflection Waveguide
Open this publication in new window or tab >>Directional coupler wavelength selective filter based on dispersive  Bragg Reflection Waveguide
2006 (English)In: Optics Communications, ISSN 0030-4018, E-ISSN 1873-0310, Vol. 260, no 2, 514-521 p.Article in journal (Refereed) Published
Abstract [en]

A new type of wavelength selective filter, based on high differential dispersion between two coupled waveguides, is presented. The Bragg Reflection Waveguide displays high effective refractive index dispersion, due to the interaction of the guided mode with the two confining Bragg reflectors. When coupled with a weakly guided buried channel silica waveguide, a very narrow bandwidth filter (< 1 nm) can be easily produced, in a shorter length, with respect to directional couplers made with standard step index channel waveguides. The complete design methodology, fabrication and characterization are presented.

Keyword
Integrated-optical waveguides, Optical devices, Optical filters, Plasma film deposition
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-4999 (URN)10.1016/j.optcom.2005.10.071 (DOI)000236594800023 ()2-s2.0-33644943394 (Scopus ID)
Note
QC 20100908. Uppdaterad från Manuskript till Artikel (20100908)Available from: 2005-03-10 Created: 2005-03-10 Last updated: 2017-12-05Bibliographically approved
9. High performance 1.55μm vertical external cavity surface emitting laser with broadband integrated dielectric-metal mirror
Open this publication in new window or tab >>High performance 1.55μm vertical external cavity surface emitting laser with broadband integrated dielectric-metal mirror
Show others...
2004 (English)In: Electronics Letters, ISSN 0013-5194, E-ISSN 1350-911X, Vol. 40, no 12, 734-735 p.Article in journal (Refereed) Published
Abstract [en]

1.55 μm room-temperature continuous-wave operation of a high performance optically pumped vertical external cavity surface emitting laser is reported. The structure includes an active region with strain compensated quantum wells, and a broadband SiNx/Si/Au Bragg reflector transferred on an Si substrate by Au/In dry bonding. Output power of up to 45 mW is achieved at 0°C, and continuous-wave operation is observed up to 45°C.

Keyword
Dielectric devices, Heat resistance, Mirrors, Optical pumping, Semiconductor lasers, Semiconductor quantum wells, Silicon, Substrates, Silicon substrates, Vertical extended-cavity surface-emitting lasers (VECSEL)
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-5001 (URN)10.1049/el:20040535 (DOI)000222386200016 ()2-s2.0-3042643202 (Scopus ID)
Note
QC 20101004Available from: 2005-03-10 Created: 2005-03-10 Last updated: 2017-12-05Bibliographically approved

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