New paper about structured THz radiation: Imaging with Airy beam

New paper by Rusnė Ivaškevičiūtė-Povilauskienė et. al just published in Light Science and Applications journal by Nature publishing group entitled ”Terahertz structured light: nonparaxial Airy imaging using silicon diffractive optics”. The work demonstrates the structured nonparaxial THz light in the form of Airy, Bessel, and Gaussian beams generated in a compact way using exclusively silicon diffractive optics prepared by femtosecond laser ablation technology. The structured THz light consistently outperforms the conventional one in resolution and contrast.

The findings open new frontiers of structured light applications in imaging and inverse scattering problems. Imaging of stacked graphene layers with THz Airy beam revealed potential to be applied for inspection of 2D materials quality.

The article is freely available under Open Access license and can be reached through the DOI address: https://doi.org/10.1038/s41377-022-01007-z


International Workshop on Nitride Semiconductors (IWN)

Head of laboratory Dr. Irmantas Kašalynas and PhD student Justinas Jorudas represented THz Photonics laboratory at International Workshop on Nitride Semiconductors (IWN) which took place in Berlin, Germany from 10th till 14th of October. Our lab presented scientific results in 1 oral and 3 poster presentations.

Head of laboratory Dr. Irmantas Kašalynas gives a talk at IWN meeting,

New study on formation and drift of space-charge domains with velocity of sound in n-type GaN

New paper by Roman Balagula et al. under the title ”Space-charge domains in n-type GaN epilayers under pulsed electric field” is published in the Applied Physics Letters.

The experimental work investigates the formation and drift of space-charge domains with velocity of sound in n-type GaN. The findings defines the constraints
for the design of GaN-based power electronic devices.

The paper can be reached through this DOI: https://doi.org/10.1063/5.0098951

THz Atelier participates at the IRMMW-THz 2022 conference in Delft, the Netherlands

From 28th of August till 2nd of September the THz Photonics laboratory is going to the 47th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz)! Our all lab is going to take part in this massive scientific event. This year we discuss very interesting scientific results in 4 oral and 6 poster presentations (10 papers in total). Let’s meet there: https://www.irmmw-thz2022.tudelft.nl/program.html

Dissipative Parametric Gain in a GaAs/AlGaAs Superlattice in PHYSICAL REVIEW LETTERS

New study is published in the journal “Physical Review Letters” from American Physical Society in the field of parametric generation of EM oscillations in GHz-THz frequency range. The work reports on the first observation of the dissipative parametric generation in a subcritically doped GaAs/AlGaAs superlattice (SL) subjected to a DC bias and a microwave pump. It enforces excitation of slow electrostatic waves in the SL that provide a significant enhancement of the gain coefficient.

The findings foresee the development of a miniature solid-state parametric generators of GHz-THz frequencies operating at room temperature.

Sketch of the parametric generation in the SL device.

DOI: 10.1103/PhysRevLett.128.236802

High-Frequency and High-Power Performance of n-Type GaN Epilayers with Low Electron Density Grown on Native Substrate

The article by Roman M Balagula et al. just published in the journal MDPI Materials. The study is aimed towards the high frequency response properties of the n-type GaN epilayers on a native stubstrates. The results indicate new practical possibilities of the GaN material controlled by an external electric field for the development of novel devices for high-power and high-frequency applications.

The work was supported by European Social Fund (project No 09.3.3-LMT-K-
712-19-0184) under grant agreement with the Research Council of Lithuania (LMT), the National Science Centre (Grant No. UMO-2017/27/L/ST7/03283) and the National Center for Research and Development (Grant No. WPC/20/DefeGaN/2018 and No. TECHMATSTRATEG-III/0003/2019/EnerGaN).

The article is published as a open access and can be accessed freely via DOI: https://doi.org/10.3390/ma15062066

Development of Quaternary InAlGaN Barrier Layer for High Electron Mobility Transistor Structures

Work by J. Jorudas et al. was recently published in the MDPI Materials journal reporting about the development of high electron mobility transistor structures based on quaternary lattice matched InAlGaN barrier layer.

The thorough study on the morphological, optical and electrical properties of the layers is accomplished aiming towards application for microwave power and terahertz plasmonic devices.

The paper is open access and is available through the link: https://doi.org/10.3390/ma15031118

The work was supported by the Research Council of Lithuania under the “TERAGANWIRE” project (Grant No. S-LL-19-1), by the National Science Center of Poland (Grant No. 2017/27/L/ST7/03283), by “International Research Agendas” program of the Foundation for Polish Science co-financed by the EU under the European Regional Development Fund (Nos. MAB/2018/9), and partially supported by the Polish National Center for Research and Development through projects No. WPC/20/DefeGaN/2018 and No. TECHMATSTRATEG-III/0003/2019.

New work published concerning advantages of optical modulation in terahertz imaging for study of graphene layers

The newest study was published in Journal of Applied Physics by Rusnė Ivaškevičiūtė-Povilauskienė et al. about the advantages of optical modulation in terahertz imaging for study of graphene layers.

It was demonstrated that optical modulation together with simultaneous terahertz (THz) imaging application enables an increase in contrast by an order of magnitude, thereby illustrating the technique as a convenient contactless tool for characterization of graphene deposited on high-resistivity silicon substrates.

The technique is applied in the development and investigation of graphene-based optical diffractive elements for THz imaging systems.

The work achieved funding from Horizon 2020 program under Grant No. 823728 (DiSetCom) as well as by the Academy of Finland Flagship Programme “Photonics Research and Innovation (PREIN)” (Decision No. 320165).

The paper is open access and can be easily reached through the DOI: https://doi.org/10.1063/5.0074772