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High quality photonic crystal waveguide filters based on mode-gap effect
KTH, School of Information and Communication Technology (ICT), Material Physics (Closed 20120101), Semiconductor Materials, HMA (Closed 20120101).
KTH, School of Information and Communication Technology (ICT), Material Physics (Closed 20120101), Semiconductor Materials, HMA (Closed 20120101).
KTH, School of Information and Communication Technology (ICT), Material Physics (Closed 20120101), Semiconductor Materials, HMA (Closed 20120101).
KTH, School of Information and Communication Technology (ICT), Material Physics (Closed 20120101), Semiconductor Materials, HMA (Closed 20120101).ORCID iD: 0000-0003-2136-4914
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2011 (English)In: Conference Proceedings: International Conference on Indium Phosphide and Related Materials, 2011Conference paper, Published paper (Refereed)
Abstract [en]

We demonstrate that the side-wall profiles of high-aspect-ratio two-dimensional (2D) photonic crystals (PhCs) in InP-based materials can be made vertical by reshaping through annealing. The annealing reduces depth and shape irregularities which are inherent to the etch-process. The efficacy of the reshaping is demonstrated by comparing the optical properties of PhC waveguides having as-etched and reshaped PhC-hole geometries. Spectral characteristics of ministop-bands (MSBs), due to coupling of third and fifth order modes with the fundamental mode, are used to qualify PhC fabrication. We demonstrate high optical quality filters based on the MSB effect (first and fifth order modes) and also use the spectral characteristics as a quality indicator of PhC fabrication. The MSBs transmission spectrum shows very sharp cut-offs for reshaped PhC waveguides. It is proposed that the reshaping process using annealing may also be beneficial for other PhC devices, nanostructure geometries and materials.

Place, publisher, year, edition, pages
2011.
Series
Conference Proceedings: International Conference on Indium Phosphide and Related Materials, ISSN 1092-8669 ; 5978354
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:kth:diva-101685Scopus ID: 2-s2.0-84863260496ISBN: 978-3-8007-3356-9 (print)OAI: oai:DiVA.org:kth-101685DiVA: diva2:548534
Conference
2011 Compound Semiconductor Week and 23rd International Conference on Indium Phosphide and Related Materials, CSW/IPRM 2011; Berlin, Germany, 22-26 May, 2011
Note

QC 20120831

Available from: 2012-08-31 Created: 2012-08-31 Last updated: 2014-09-03Bibliographically approved
In thesis
1. Technology and properties of InP-based photonic crystal structures and devices
Open this publication in new window or tab >>Technology and properties of InP-based photonic crystal structures and devices
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Photonic crystals (PhCs) are periodic dielectric structures that exhibit a photonic band gap; a range of wavelengths for which light propagation is forbidden. 2D PhCs exhibit most of the properties as their three dimension counterparts with a compatibility with standard semiconductor processing techniques such as epitaxial growth, electron beam lithography, Plasma deposition/etching and electromechanical lapping/polishing. Indium Phosphide (InP) is the material of choice for photonic devices especially when it comes to realization of coherent light source at 1.55 μm wavelength. Precise engineering of the nanostructures in the PhC lattice offers novel ways to confine, guide and control light in phonic integrated circuits (PICs). Strong confinement of light in PhCs offer novel opportunities in many areas of physics and engineering.

Dry etching, a necessary process step in PhC device manufacturing, is known to introduce damage in the etched material. Process induced damage and its impact on the electrical and optical properties of PhCs depends on the etched material, the etching technique and process parameters. We have demonstrated a novel post-etch process based on so-called mass-transport (MT) technology for the first time on InP-based PhCs that has significantly improved side-wall verticality of etched PhC holes. A statistical analysis performed on several devices fabricated by MT process technology shows a great deal of improvement in the reliability of optical transmission characteristics which is very promising for achieving high optical quality in PhC components. Several PhC devices were manufactured using MT technology.

Broad enough PhC waveguides that operate in the mono/multi-mode regime are interesting for coarse wavelength de-multiplexing. The fundamental mode and higher order mode interaction creates mini-stop band (MSB) in the dispersion diagram where the higher order mode has a lower group velocity which can be considered as slow light regime. In this thesis work, the phenomena of MSBs and its impact on transmission properties have been evaluated. We have proposed and demonstrated a method that enables spectral tuning with sub-nanometer accuracy which is based on the transmission MSB. Along the same lines most of the thesis work relates to broad enough PhC guides that operated in the multimode regime. Temperature tuning experiments on these waveguides reveals a clear red-shift with a gradient of dλ/dT=0.1 nm/˚C. MSBs in these waveguides have been studied by varying the width in incremental amounts.

Analogous to semiconductors heterostructures, photonic heterostructures are composed of two photonic crystals with different band-gaps obtained either by changing the air-fill factor or by the lattice constant. Juxtaposing two PhC and the use of heterostructures in waveguide geometry has been experimentally investigated in this thesis work. In particular, in multimode line defect waveguides the “internal” MSB effect brings a new dimension in single junction-type photonic crystal waveguide (JPCW) and heterostructure W3 (HW3) for fundamental physics and applications. We have also fabricated an ultra-compact polarization beam splitter (PBS) realized by combining a multimode waveguide with internal PhC. MSBs in heterostructure waveguides have shown interesting applications such as designable band-pass flat-top filters, and resonance-like filters with high transmission.

In the course of this work, InGaAsP suspended membrane technology was developed. An H2 cavity with a linewidth of ~0.4 nm, corresponding to a Q value of ~3675 has been shown. InGaAsP PhC membrane is an ideal platform to study coupled quantum well/dot-nanocavity system.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. xii, 64 p.
Series
Trita-ICT/MAP AVH, ISSN 1653-7610 ; 2012:14
Keyword
Integrated optics materials, Photonic crystals, Planar waveguides, Dispersion, Band-gap, Mode-gap, mini-stopband, InP, Nanostructure fabrication, dry etching, mass transport; material reflow; reliability
National Category
Engineering and Technology Natural Sciences
Research subject
SRA - ICT
Identifiers
urn:nbn:se:kth:diva-101662 (URN)978-91-7501-442-5 (ISBN)
Public defence
2012-09-17, Sal C2, Electrum 229 Isafjordsgatan 22-26, Kista, 10:00 (English)
Opponent
Supervisors
Funder
Swedish Research Council
Note

QC 20120831

Available from: 2012-08-31 Created: 2012-08-30 Last updated: 2012-09-24Bibliographically approved

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Swillo, Marcin

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