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Ultrasharp ministop-band edge for subnanometer tuning resolution
KTH, School of Information and Communication Technology (ICT), Material Physics, Semiconductor Materials, HMA.
KTH, School of Information and Communication Technology (ICT).
KTH, School of Information and Communication Technology (ICT), Material Physics, Semiconductor Materials, HMA.
KTH, School of Information and Communication Technology (ICT), Material Physics, Semiconductor Materials, HMA.
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2011 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 98, no 8, 081112- p.Article in journal (Refereed) Published
Abstract [en]

We propose and demonstrate a method that enables spectral tuning with subnanometer accuracy, and is based on the transmission ministop-band (MSB) in line-defect multimode photonic crystal (PhC) waveguides. The fabricated MSB filter has ultrasharp edges which show a 30 dB drop in transmission in a 4 nm wavelength span. The use of the ultrasharp MSB edge to (optically) determine PhC fabrication accuracy is demonstrated. The wavelength position of the MSB could be tuned by temperature, with a coefficient of 0.1 nm/degrees C. The spectral characteristics of the MSB realized in this work are promising for sensing, tuning, and modulation applications.

Place, publisher, year, edition, pages
2011. Vol. 98, no 8, 081112- p.
Keyword [en]
National Category
Other Engineering and Technologies
URN: urn:nbn:se:kth:diva-31378DOI: 10.1063/1.3559915ISI: 000287764300012ScopusID: 2-s2.0-79952074215OAI: diva2:403894
QC 20110315Available from: 2011-03-15 Created: 2011-03-14 Last updated: 2012-08-31Bibliographically 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.
Trita-ICT/MAP AVH, ISSN 1653-7610 ; 2012:14
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
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)
Swedish Research Council

QC 20120831

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

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