Category: sci. papers

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IRMMW-THz 2023

This week the lab staff is visiting Montreal, Canada, for 48th International Conference on Infrared , Millimeter, and Terahertz Waves. It is indeed the main event in the field of terahertz research. This year Terahertz Photonics Laboratory contributed 8 talks in various THz research fields.

Here are the list of presentations and the presenting authors:

Nonparaxial Imaging Using Terahertz Structured Light by Gintaras Valušis et al.

Terahertz And DC Conductivity Of Pyrolyzed Photoresist Films by Justinas Jorudas et al.

This Study Explores The Use Of Passive And Flexible Optics Elements To Achieve THz Beam Profile Engineering For Imaging Applications Via Mechanical Bending by Linas Minkevičius et al.

THz Detection Optimization Of Antenna Coupled AlGaN/GaN High Electron Mobility Transistors by Maxim Moscotin et al.

A Design And Performance Of A Low-cost THz Imaging System Using InP Gunn Diode Emitter, Paraffin Wax Optics And Commercially Available GaAs HEMTs by Linas Minkevičius et al.

Coherent Thermal Emission From Circular N-GaN Surface Relief Gratings 100% by Vytautas Janonis et al.

Two- And Four-step Phase Shifting Methods For Terahertz Holography by Rusnė Ivaskevičiūtė-Povilauskienė et al.

Polarization Selective Dual Frequency Metasurface-based Resonant Thermal Terahertz Emitters On N-GaAs/GaAs by Ignas Grigelionis et al.

The link to conference webpage: https://www.irmmw-thz.org/conference/

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Coexistence of Bloch and Parametric Mechanisms of High-Frequency Gain in Doped Superlattices

New open access article is published in the journal Nanomaterials (MDPI) by Vladislovas Čižas, Natalia Alexeeva, Kirill N. Alekseev and Gintaras Valušis. Theoretical study dives into the physical mechanisms of high-frequency gain in a doped semiconductor superlattice

The findings of the research contributes to the advancement of new miniature GHz–THz frequency generators, amplifiers, and dividers operating at room temperature.

The research was partially funded by the Marius Jakulis Jason Foundation and the Research Council of Lithuania (No 01.2.2-LMT-K-718-03-0096).

The paper can be reached through this DOI: . https://doi.org/10.3390/nano13131993

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Electro-optical modulation of terahertz beam by drifting space-charge domains in n-GaN epilayers

The research article by Roman B. Balagula, Liudvikas Subačius, Paweł Prystawko, and Irmantas Kašalynas is published in Journal of Applied Physics, AIP Publishing. The work entitled “Electro-optical modulation of terahertz beam by drifting space-charge domains in n-GaN epilayers” investigates the transmission modulation of THz field in GaN semiconductor as a response to space-charge domains under near-to-breakdown electrical field conditions.

Traces of charge current density j, the electro-optic modulation of THz beam transmission ΔTeo, and the sample specific resistance, Edc/j, found as a ratio between measurements of applied electric field and current density traces.

The open access research article is available through https://doi.org/10.1063/5.0152661

The work was supported by the Research Council of Lithuania through the “Hybrid plasmonic components for THz range (T-HP)” Project (Grant No. DOTSUT-184) funded by the European Regional Development Fund according to the supported activity “Research Projects Implemented by World-class Researcher Groups” under the Measure No. 01.2.2-LMT-K-718-03-0096. The work at Warsaw was supported by the National Center for Research and Development (Grant No. TECHMATSTRATEG-III/0003/2019/EnerGaN).

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Narrowband Thermal Terahertz Emission of Ti/Au Metasurface on Homoepitaxial GaAs

New work by I. Grigelionis et al. was published in the scientific journal Sensors from MDPI publisher. Authors report on the experimental evidence of thermal terahertz emission tailored by magnetic polariton excitations in entirely GaAs-based structures equipped with metasurfaces. Thermal emission was measured at 390 C temperature in the range from 0.7 THz to 1.3 THz, depending on the size of the square metacells.

The magnetic polariton resonance quality factors obtained at elevated temperatures (Q ~ 3.3 to 5.2) are very similar to those of MIM structures as well as to 2D plasmon resonance quality at cryogenic temperatures.

The open access paper can be reached through https://doi.org/10.3390/s23104600

This research has received funding from the Research Council of Lithuania (LMTLT), agreement No. S-MIP-22-76.

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A Review: Semiconductor Characterization by Terahertz Excitation Spectroscopy

A comprehensive review written by Arūnas Krotkus, Ignas Nevinskas and Ričardas Norkus on the terahertz excitation spectroscopy and it’s applications is recently published in the journal “Materials” by MDPI Publisher. The experimental technique known as the THz excitation spectroscopy is used as a contactless method to study the band structure and investigate the ultrafast processes of various technologically important materials. A recent decade of investigations with the THz excitation spectroscopy method is reviewed in this paper.

The review is available as an open access publication through this DOI: https://doi.org/10.3390/ma16072859


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The 2023 terahertz science and technology roadmap

New roadmap for THz science and technology is just published in the Journal of Physics D: Applied Physics by IOP Publishing. Among the number of distinguished authors one can find Gintaras Valušis who have significantly contributed to the publication. Congratulations!

The roadmap is a collection of sections addressing the particular aspects of latest THz technology developments. It is indeed the excellent source to get the insights to the future of THz science.

The publication under open access license can be accessed trough this DOI: https://doi.org/10.1088/1361-6463/acbe4c

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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


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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

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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

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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