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Influence of Ge content on the optical quality of Plasma CVD deposited Silica films
KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.ORCID iD: 0000-0001-5967-2651
2002 (English)Conference 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.

Place, publisher, year, edition, pages
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
URN: urn:nbn:se:kth:diva-4995OAI: diva2:7372
American Vacuum Society’s 49th International Symposium

NR 20160427

Available from: 2005-03-10 Created: 2005-03-10 Last updated: 2016-04-27Bibliographically approved
In thesis
1. Plasma assisted technology for Si-based photonic integrated circuits
Open this publication in new window or tab >>Plasma assisted technology for Si-based photonic integrated circuits
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.
Trita-MVT, ISSN 0348-4467 ; 2005:2
Electrical engineering, silica-on-silicon technology, PACVD, plasma deposition, photonic integrated circuits, planar lightwave circuits, Elektroteknik, elektronik och fotonik
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
urn:nbn:se:kth:diva-148 (URN)
Public defence
2005-03-21, Sal C1, KTH-Electrum, Isafjordsgatan 22, Kista, 10:00 (English)
QC 20101004Available from: 2005-03-10 Created: 2005-03-10 Last updated: 2010-10-04Bibliographically approved

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