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Effects of surface roughness on the performance of an etched diffraction grating demultiplexer
KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
Zhejiang University.
KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.ORCID iD: 0000-0002-3401-1125
2006 (English)In: Journal of the Optical Society of America A: Optics and Image Science, and Vision, ISSN 1084-7529, Vol. 23, no 3, 646-650 p.Article in journal (Refereed) Published
Abstract [en]

The fabrication tolerance of surface roughness on the performance [such as the insertion loss, the polarization-dependent loss (PDL), and the chromatic dispersion] of an etched diffraction grating demultiplexer is analyzed by using an accurate method of moments. The results show that both the insertion loss and the chromatic dispersion rapidly increase as the roughness of the grating facets increases. Appropriate residual roughness of the shaded facets can reduce the PDL of the demultiplexer, and the mechanism for the existence of an optimal residual roughness is explained.

Place, publisher, year, edition, pages
2006. Vol. 23, no 3, 646-650 p.
Keyword [en]
Demultiplexing, Diffraction, Insertion losses, Light polarization, Optical communication, Optical waveguides, Surface roughness, Wavelength division multiplexing, Chromatic dispersion, Diffraction grating demultiplexer, Polarization dependent loss (PDL)
National Category
Telecommunications
Identifiers
URN: urn:nbn:se:kth:diva-8608DOI: 10.1364/JOSAA.23.000646ISI: 000235747900017Scopus ID: 2-s2.0-33645416558OAI: oai:DiVA.org:kth-8608DiVA: diva2:13976
Note
QC 20100910Available from: 2008-06-02 Created: 2008-06-02 Last updated: 2013-11-19Bibliographically approved
In thesis
1. Electromagnetic simulation and design of etched diffraction grating demultiplexers
Open this publication in new window or tab >>Electromagnetic simulation and design of etched diffraction grating demultiplexers
2008 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

Among various planar lightwave circuits for multiplexing/demultiplexing in an optical communication system, etched diffraction gratings (EDGs) have shown great potential due to their compactness and high spectral finesse. Conventional numerical methods for grating simulation cannot be used to simulate an EDG demultiplexer of large size (in terms of the wavelength). In the present thesis, the polarization-dependent characteristics of an EDG demultiplexer are analyzed with a boundary element method (BEM) for both an echelle grating coated with a metal and a dielectric grating with total internal reflection (TIR) facets. For EDGs with metal-coated facets, we use a more effective method, namely, method of moments (MoM). Futhermore, a fast simulation method for EDGs with TIR facets is presented based on the Kirchhoff–Huygens principle and the Goos-Hänchen shift. This simple method has a good agreement with a BEM over a wide range of practical parameters of the device.

Several novel designs are presented in order to improve the performances of EDGs. (1) By making some appropriate roughness on the surface of the shaded facets, the PDL of the demultiplexer can be effectively reduced over a large bandwith. (2) For EDGs based on Si nanowire structures, we compensate the polarization-dependent wavelength dispersion (PDλ) in the whole operational spectrum by introducing a polarization compensation area in its free propagation region. (3) An EDG demultiplexer with suppressed sidelobe is designed. The designed EDG demultiplexer can give a crosstalk as small as 50 dB in theory. (4) By chirping the diffraction order for each facet, we minimize the envelope intensity for the other adjacent diffraction orders to achieve a negligible return loss in a large spectral width. (5) A design for EDG demultiplexers is presented to obtain both large grating facets and a larger free spectral range (FSR) using the optimal chirped diffraction orders for different facets.

The influences of the fabrication errors (e.g., rounded effect, surface roughness and point defect in the waveguide) on the performance (such as the insertion loss, the polarization dependent loss and the chromatic dispersion) of an EDG demultiplexer are also analyzed in detail.

Silicon nanowire waveguides and related EDGs are studied. An EDG demultiplexer with 10 nm spacing is finally fabricated and characterized.

Place, publisher, year, edition, pages
Stockholm: KTH, 2008. X, 113 p.
Series
Trita-EE, ISSN 1653-5146 ; 2008:078
Keyword
etched diffraction grating, wavelength division multiplexing, passive devices, diffraction grating, planar waveguide devices, DWDM, optical communication.
National Category
Telecommunications
Identifiers
urn:nbn:se:kth:diva-4791 (URN)
Public defence
2008-06-11, Entreplan D3, Lindstedtsv 5, main campus of KTH, 10:00
Opponent
Supervisors
Note
QC 20100910Available from: 2008-06-02 Created: 2008-06-02 Last updated: 2010-09-10Bibliographically approved

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He, Sailing

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