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Optically controlled dielectric properties of single-walled carbon nanotubes for terahertz wave applications
KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Micro and Nanosystems.ORCID iD: 0000-0003-0368-1668
KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Micro and Nanosystems.ORCID iD: 0000-0002-6260-2694
ITMO University.ORCID iD: 0000-0003-4948-2023
ITMO University.ORCID iD: 0000-0002-5799-3379
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2018 (English)In: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 10, no 26, p. 12291-12296Article in journal (Refereed) Published
Abstract [en]

Materials with tunable dielectric properties are valuable for a wide range of electronic devices, but are often lossy at terahertz frequencies. Here we experimentally report the tuning of the dielectric properties of single-walled carbon nanotubes under light illumination. The effect is demonstrated by measurements of impedance variations at low frequency as well as complex dielectric constant variations in the wide frequency range of 0.1-1 THz by time domain spectroscopy. We show that the dielectric constant is significantly modified for varying light intensities. The effect is also practically applied to phase shifters based on dielectric rod waveguides, loaded with carbon nanotube layers. The carbon nanotubes are used as tunable impedance surface controlled by light illumination, in the frequency range of 75-500 GHz. These results suggest that the effect of dielectric constant tuning with light, accompanied by low transmission losses of the carbon nanotube layer in such an ultra-wide band, may open up new directions for the design and fabrication of novel Terahertz and optoelectronic devices.

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2018. Vol. 10, no 26, p. 12291-12296
Keywords [en]
Requency-Range, Millimeter, Conductivity, Technology, Guides
National Category
Nano Technology
Identifiers
URN: urn:nbn:se:kth:diva-230899DOI: 10.1039/C8NR03740JISI: 000438246000006PubMedID: 29926050Scopus ID: 2-s2.0-85049850363OAI: oai:DiVA.org:kth-230899DiVA, id: diva2:1222486
Funder
EU, Horizon 2020, 675683EU, Horizon 2020, 616846
Note

QC 20180625

Available from: 2018-06-21 Created: 2018-06-21 Last updated: 2022-11-30Bibliographically approved
In thesis
1. Tunable Nanomaterials and their Applications for Terahertz Devices: Carbon Nanotubes and Silver Nanowires
Open this publication in new window or tab >>Tunable Nanomaterials and their Applications for Terahertz Devices: Carbon Nanotubes and Silver Nanowires
2021 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The interest in terahertz (THz) technologies is growing in academia and industry. The design of electronic components at THz frequencies is relevant to application areas such as telecommunication, radar, material spectroscopy, and medical imaging and diagnosis. Even though high-performance THz instrumentation becomes more available, the systems are not commonly found outside of the laboratory environment. Researchers have recently demonstrated a platform based on dielectric rod waveguides (DRWs) that is suitable for integrating THz electronics. The electromagnetic waves propagate inside a low-loss dielectric structure, a concept similar to optical fibres. DRWs have seen many advances for THz electronics in recent years. However, the platform still lacks essential active and passive components for building complete systems. 

This thesis investigates ways to integrate tunable nanomaterials to dielectric waveguides in order to design novel terahertz devices. First, silicon rectangular DRWs are investigated at 75 GHz to 500 GHz frequencies. In particular, the interface with the measurement instrumentation and the tapered transitions to hollow metallic waveguides are considered by electromagnetic simulations. Additionally, ways to implement phase shifters and attenuators are explored using thin layers of nanomaterials that are modelled by an impedance surface in the simulations. 

Second, several nanomaterials are studied by optical spectrophotometry, Raman spectroscopy, and terahertz time-domain and frequency- domain spectroscopy. Thin layers of silver nanowires are fabricated with increasing densities, ranging from individual nanowires to nanowire networks at the percolation threshold, to thick semi-continuous layers. This technique allows the manufacturing of optically transparent samples with a tunable THz conductivity. Additionally, thin layers of single-walled carbon nanotubes are investigated. Their dielectric properties are shown to be tunable by light illumination, supported by measurements at low frequencies and in the terahertz range. 

Finally, tunable THz devices based on dielectric waveguides are designed, manufactured, and characterized. Thin layers of carbon nanotubes are integrated with DRWs and used as a surface impedance to modify the wave propagation in the waveguide. The presented phase shifters are tunable by light with wideband operation at sub-THz and potentially higher frequencies, and further device improvements are proposed. 

Abstract [sv]

Intresset för terahertz (THz) -teknologi ökar både i den akademiska världen och inom industrin. Design av elektroniska komponenter i THz-frekvenser är relevanta för applikationsområden som telekommunikation, radar, materialspektroskopi och medicinsk bildbehandling och diagnostik. Även om högpresterande THz-instrumentering blir mer tillgängligt finns systemen ofta inte utanför laboratoriemiljöer. Forskare har nyligen demonstrerat en plattform baserad på dielektriska vågledare (DRWs) som är lämplig för att integrera THz-elektronik. De elektromagnetiska vågorna sprids inuti en lågförlustdielektrisk struktur, ett koncept som liknar den optiska fibern. DRW har sett många framsteg för THz-elektronik på senare år. Plattformen saknar dock fortfarande väsentliga aktiva och passiva komponenter för att bygga kompletta system. 

Denna avhandling undersöker olika sätt att integrera avstämbara nanomaterial till dielektriska vågledare för att designa nya terahertzenheter. Först undersöks rektangulära kisel-DRWs vid frekvenserna 75 GHz till 500 GHz. I synnerhet används elektromagnetiska simuleringar för att efterlikna gränssnittet mellan mätinstrumentet och de avsmalnande övergångarna till de ihåliga metalliska vågledarna. Dessutom utforskas sätt för att implementera  fasväxlare och dämpare med hjäp av tunna lager av nanometrial som modelleras av en impedansyta i simuleringarna. 

Sedan studeras även flera nanomaterial genom optisk spektrofotometri, Ramanspektroskopi och terahertztidsdomän- och frekvensdomänspektroskopi. Tunna lager av silvernanotrådar tillverkas med ökande densiteter, allt från enskilda nanotrådar till nanotrådsnät vid perkolationströskeln, till tjockare halvkontinuerliga lager. Denna teknik möjliggör tillverkning av optiskt transparenta prover med en avstämbar THz-konduktivitet. Dessutom undersöks tunna lager av enkelväggiga kolnanorör. Deras dielektriska egenskaper påvisas vara avstämbara med belysning, vilket även stöds av mätningar vid låga frekvenser och i terahertz-omfånget. 

Slutligen designas, tillverkas och karakteriseras inställbara THz-enheter baserade på dielektriska vågledare. Tunna lager av kolnanorör integreras med DRW och används som ytimpedans för att ändra vågutbredningen i vågledaren. De presenterade fasskiftarna kan ställas in med hjälp av ljus med bredbandsoperationer vid sub-THz och potentiellt högre frekvenser, även ytterligare enhetsoptimeringar föreslås.

Place, publisher, year, edition, pages
Stockholm, Sweden: KTH Royal Institute of Technology, 2021. p. 61
Series
TRITA-EECS-AVL ; 2021:33
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-293982 (URN)978-91-7873-878-6 (ISBN)
Public defence
2021-06-07, MST Conference Room, Malvinas väg 10, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20210518

Available from: 2021-05-18 Created: 2021-05-11 Last updated: 2022-06-25Bibliographically approved

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Smirnov, SergueiAnoshkin, Ilya V.Lioubtchenko, Dmitri V.Oberhammer, Joachim

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