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Technology and properties of InP-based photonic crystal structures and devices
KTH, School of Information and Communication Technology (ICT), Material Physics, Semiconductor Materials, HMA.
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 [en]
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: urn:nbn:se:kth:diva-101662ISBN: 978-91-7501-442-5 (print)OAI: oai:DiVA.org:kth-101662DiVA: diva2:548469
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
List of papers
1. Novel postetch process to realize high quality photonic crystals in InP
Open this publication in new window or tab >>Novel postetch process to realize high quality photonic crystals in InP
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2011 (English)In: Journal of Vacuum Science & Technology B, ISSN 1071-1023, E-ISSN 1520-8567, Vol. 29, no 3, 031202- p.Article in journal (Refereed) Published
Abstract [en]

Thermally driven reflow of material during annealing was positively used to obtain near-vertical sidewall profiles for high-aspect-ratio nanostructures in InP fabricated by dry etching. This is very promising for achieving high optical quality in photonic crystal (PhC) components. Nearly cylindrical profiles were obtained for high-aspect-ratio PhC holes with diameters as small as 200350 nm. Mini stop bands (MSBs) in line-defect PhC waveguides were experimentally investigated for both as-etched and reshaped hole geometries, and their spectral characteristics were used to assess the quality of PhC fabrication. The spectral characteristics of the MSB in PhC waveguides with reshaped holes showed significant improvement in performance with a transmission dip as deep as 35 dB with sharp edges dropping in intensity more than 30 dB for similar to 4 nm of wavelength change. These results show potential for using high extinction drop-filters in InP-based monolithic photonic integrated circuit applications. Finally, it is proposed that other nanostructure geometries may also benefit from this reshaping process.

Keyword
MINI-STOP-BAND; WAVE-GUIDES; SLOW-LIGHT; LASER; FABRICATION
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-35123 (URN)10.1116/1.3574760 (DOI)000291111300007 ()2-s2.0-79958096444 (Scopus ID)
Note
QC 20110623Available from: 2011-06-23 Created: 2011-06-20 Last updated: 2017-12-11Bibliographically approved
2. Experimental demonstration of an ultracompact polarization beamsplitter based on a multimode interference coupler with internal photonic crystals
Open this publication in new window or tab >>Experimental demonstration of an ultracompact polarization beamsplitter based on a multimode interference coupler with internal photonic crystals
Show others...
2010 (English)In: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 49, no 6, 060503- p.Article in journal (Refereed) Published
Abstract [en]

The fabrication and characterization of a compact InP-based polarization beamsplitter (PBS) is presented. A multimode interference (MMI) coupler with an internal air hole photonic crystal (PhC) section is utilized to separate the two polarizations. The PhC structure in the middle of the MMI is polarization dependent, so that one polarization is reflected and the other one is transmitted; both are collected by the respective output ports of the MMI coupler. The obtained experimental results show that the PBS as short as similar to 400 mu m has an extinction ratio as large as 15 dB.

Keyword
polarization beamsplitter, multimode interference, photonic crystal, InP
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:kth:diva-26874 (URN)10.1117/1.3454377 (DOI)000280746600003 ()2-s2.0-80855129213 (Scopus ID)
Note
QC 20101130Available from: 2010-11-30 Created: 2010-11-29 Last updated: 2017-12-12Bibliographically approved
3. High quality photonic crystal waveguide filters based on mode-gap effect
Open this publication in new window or tab >>High quality photonic crystal waveguide filters based on mode-gap effect
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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.

Series
Conference Proceedings: International Conference on Indium Phosphide and Related Materials, ISSN 1092-8669 ; 5978354
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-101685 (URN)2-s2.0-84863260496 (Scopus ID)978-3-8007-3356-9 (ISBN)
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
4. Ultrasharp ministop-band edge for subnanometer tuning resolution
Open this publication in new window or tab >>Ultrasharp ministop-band edge for subnanometer tuning resolution
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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.

Keyword
CRYSTAL WAVE-GUIDES, PHOTONIC CRYSTALS, STOP-BAND, SLAB, DEVICES, DEPENDENCE, INDEX, LIGHT
National Category
Other Engineering and Technologies
Identifiers
urn:nbn:se:kth:diva-31378 (URN)10.1063/1.3559915 (DOI)000287764300012 ()2-s2.0-79952074215 (Scopus ID)
Note
QC 20110315Available from: 2011-03-15 Created: 2011-03-14 Last updated: 2017-12-11Bibliographically approved
5. Junction-type photonic crystal waveguides for notch- and pass-band filtering
Open this publication in new window or tab >>Junction-type photonic crystal waveguides for notch- and pass-band filtering
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2011 (English)In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 19, no 21, 21074-21080 p.Article in journal (Refereed) Published
Abstract [en]

Evolution of the mode gap and the associated transmission mini stop-band (MSB) as a function of photonic crystal (PhC) waveguide width is theoretically and experimentally investigated. The change of line-defect width is identified to be the most appropriate way since it offers a wide MSB wavelength tuning range. A high transmission narrow-band filter is experimentally demonstrated in a junction-type waveguide composed of two PhC waveguides with slightly different widths. The full width at half maximum is 5.6 nm; the peak transmission is attenuated by only 5 dB and is 20 dB above the MSBs. Additionally, temperature tuning of the filter were also performed. The results show red-shift of the transmission peak and the MSB edges with a gradient of dλ/dT $=$ 0.1 nm/°C. It is proposed that the transmission MSBs in such junction-type cascaded PhC waveguides can be used to obtain different types of filters.

Keyword
Guided waves; Integrated optics materials; Systems design ; Waveguides, planar; Photonic integrated circuits; Dispersion; Photonic crystals
National Category
Engineering and Technology Natural Sciences
Identifiers
urn:nbn:se:kth:diva-44514 (URN)10.1364/OE.19.021074 (DOI)000296065700128 ()2-s2.0-80053961154 (Scopus ID)
Funder
Swedish Research Council
Note
QC 20111114Available from: 2011-10-22 Created: 2011-10-21 Last updated: 2017-12-08Bibliographically approved
6. Mini-stop bands in single heterojunction photonic crystal waveguides
Open this publication in new window or tab >>Mini-stop bands in single heterojunction photonic crystal waveguides
2013 (English)In: AIP Advances, ISSN 2158-3226, E-ISSN 2158-3226, Vol. 3, no 3, 032136- p.Article in journal (Refereed) Published
Abstract [en]

Spectral characteristics of mini-stop bands (MSB) in line-defect photonic crystal (PhC) waveguides and in heterostructure PhC waveguides having one abrupt interface are investigated. Tunability of the MSB position by air-fill factor heterostructure PhC waveguides is utilized to demonstrate different filter functions, at optical communication wavelengths, ranging from resonance-like to wide band pass filters with high transmission. The narrowest filter realized has a resonance-like transmission peak with a full width at half maximum of 3.4 nm. These devices could be attractive for coarse wavelength selection (pass and drop) and for sensing applications.

Keyword
High transmission, Optical communication wavelength, Photonic crystal (phc) waveguide, Photonic crystal waveguide, Sensing applications, Spectral characteristics, Transmission peaks, Wavelength selection
National Category
Other Engineering and Technologies
Identifiers
urn:nbn:se:kth:diva-101686 (URN)10.1063/1.4798304 (DOI)000316951200036 ()2-s2.0-84875869441 (Scopus ID)
Funder
Swedish Research Council
Note

QC 20130508. Updated from submitted to published.

Available from: 2012-08-31 Created: 2012-08-31 Last updated: 2017-12-07Bibliographically approved
7. Effect of hole shapes on the reliability of deeply-etched InP-based photonic crystal devices
Open this publication in new window or tab >>Effect of hole shapes on the reliability of deeply-etched InP-based photonic crystal devices
2012 (English)In: Physica Status Solidi. C, Current topics in solid state physics, ISSN 1610-1634, E-ISSN 1610-1642, Vol. 9, no 7, 1670-1673 p.Article in journal (Refereed) Published
Abstract [en]

We present systematic evaluation of the optical transmission characteristics of a set of photonic crystal waveguides (PhCWs) fabricated by two schemes. An optimized hole-reshaping process to obtain cylindrical holes was applied in one scheme and a comparison is made with as-etched PhCWs. The spectral characteristics of the transmission mini- stopband (MSB) in identical waveguides show that the reliability, in terms of spectral position and shape, of fabricated PhCWs using the hole reshaping process is significantly improved in comparison to the as-etched waveguides. The obtained MSB characteristics are attractive for coarse WDM filtering and wavelength selective mirrors.

Keyword
Dry etching, Mass transport, Material reflow, Mini-stopband, Photonics crystals, Reliability, Waveguide
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-100451 (URN)10.1002/pssc.201100670 (DOI)000306479300042 ()2-s2.0-84864023322 (Scopus ID)
Conference
16th International Semiconducting and Insulating Materials Conference (SIMC-XVI) Location: Royal Inst Technol (KTH), Stockholm, Sweden Date: JUN 19-23, 2011
Note
QC 20120808Available from: 2012-08-08 Created: 2012-08-08 Last updated: 2017-12-07Bibliographically approved

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