Lithuanian Journal of Physics article / Lietuvos fizikos žurnalo straipsnis

BRIDGING THE TERAHERTZ GAP USING SOLID-STATE DEVICES
Dalius Seliuta^a, Linas Minkevičius^a,c, Ignas Grigelionis^a, Alvydas Lisauskas^a,b, Dovilė Čibiraitė-Lukenskienė^a,b, Kęstutis Ikamas^a,b, Sergey Orlov^a, Rusnė Ivaškevičiūtė-Povilauskienė^a, Justinas Jorudas^a, Vytautas Janonis^a, Irmantas Kašalynas^a,b, Simonas Driukas^a, Vladislovas Čižas^a,c, Kirill N. Alekseev^a, and Gintaras Valušis^a
^aDepartment of Optoelectronics, Center for Physical Sciences and Technology, Saulėtekio 3, 10257 Vilnius, Lithuania
^bInstitute of Applied Electrodynamics and Telecommunications, Faculty of Physics, Vilnius University,
Saulėtekio 3, 10257 Vilnius, Lithuania
^cInstitute of Photonics and Nanotechnology, Faculty of Physics, Vilnius University, Saulėtekio 3,
10257 Vilnius, Lithuania
Email: gintaras.valusis@ff.vu.lt

Received 7 December 2025; accepted 8 December 2025

Terahertz (THz) frequencies nestled between the microwave and infrared ranges in the electromagnetic spectrum radiation remain one of the most attractive research topics. A particular attention is given to the issues related to the development of solid-state-based room-temperature high-power, stable and portable terahertz emitters and detectors as well as user-friendly THz imaging and spectroscopy. At the dawn of this research, four decades ago, academician Juras Požela [J. Požela and V. Jucienė, Physics of High-Speed Transistors (Vilnius, Mokslas, 1985)] considered possible physical mechanisms – hot electrons, plasma effects, Josephson junctions, masers, etc. – that can successfully be employed to cover the THz frequencies using solid-state physics approaches. In this work, we briefly overview the recent achievements and advances illustrating an incredibly high precision of the scientific predictions given by Acad. Juras Požela based on his wide erudition, deeply sensitive intuition and great insights, gifted feeling of scientific trends and evolution. The paper presents a structured snapshot of the modern devices with highlights in their physics behind the operation and main parameters and includes contemporary topics in THz science and technology related to electrically pumped GaN-based sources and quantum semiconductor structures such as resonant tunnelling diodes, quantum cascade lasers, and quantum semiconductor superlattices. Possible challenges in further development of the described approaches and devices are illuminated.
Keywords: terahertz, hot electrons, Gunn effect, plasma waves, field-effect transistors, thermal emitters, quantum structures, Josephson junctions

TERAHERCŲ DAŽNIŲ RUOŽO APRĖPTIS NAUDOJANT KIETOJO KŪNO PRIETAISUS
Dalius Seliuta^a, Linas Minkevičius^a,c, Ignas Grigelionis^a, Alvydas Lisauskas^a,b, Dovilė Čibiraitė-Lukenskienė^a,b, Kęstutis Ikamas^a,b, Sergey Orlov^a, Rusnė Ivaškevičiūtė-Povilauskienė^a, Justinas Jorudas^a, Vytautas Janonis^a, Irmantas Kašalynas^a,b, Simonas Driukas^a, Vladislovas Čižas^a,c, Kirill N. Alekseev^a, Gintaras Valušis^a

^aFizinių ir technologijos mokslų centro Optoelektronikos skyrius, Vilnius, Lietuva
^bVilniaus universiteto Fizikos fakulteto Taikomosios elektrodinamikos ir telekomunikacijų institutas, Vilnius, Lietuva
^cVilniaus universiteto Fizikos fakulteto Fotonikos ir nanotechnologijų institutas, Vilnius, Lietuva

Darbe trumpai apžvelgiami naujausi moksliniai pasiekimai ir pažanga, iliustruojantys neįtikėtiną akad. Juro Poželos dar 1985 m. pateiktų mokslinių prognozių tikslumą, pagrįstą jo plačia erudicija, jautria intuicija ir puikiomis įžvalgomis bei įstabiu mokslo tendencijų ir jų evoliucijos pojūčiu. Straipsnyje pateikiama struktūrizuota šiuolaikinių prietaisų apžvalga, pabrėžiant jų veikimo fiziką ir pagrindinius parametrus, taip pat aptariamos šiuolaikinės terahercų mokslo ir technologijų temos, susijusios su elektriškai kaupinamais GaN šaltiniais bei kvantinių puslaidininkinių elementų, prietaisų ir darinių, tokių kaip rezonansiniai tuneliniai diodai, kvantiniai kaskadiniai lazeriai ir kvantinių puslaidininkinių supergardelės, tyrimai. Aptariami galimi iššūkiai, susiję su aprašytų prietaisų tolesniu vystymu ir plėtra.

References / Nuorodos

[1] J. Požela and V. Jucienė, Physics of High-speed Transistors (Vilnius, Mokslas, 1985) [in Russian],
https://doi.org/10.1007/978-1-4899-1242-8
[2] M. Dyakonov and M.S. Shur, Shallow water analogy for a ballistic field effect transitor: New mechanism of plasma wave generation by dc current, Phys. Rev. Lett. 71, 2465–2468 (1993),
https://doi.org/10.1103/PhysRevLett.71.2465
[3] J. Faist, F. Cappaso, D.L. Sivco, C. Sirtori, A.L. Hutchinson, and A.Y. Cho, Quantum cascade laser, Science 264, 553–556 (1994),
https://doi.org/10.1126/science.264.5158.553
[4] R. Köhler, A. Tredicucci, F. Beltram, H.E. Beere, E.H. Linfeld, A.G. Davies, D.A. Ritchie, R.C. Iotti, and F. Rossi, Terahertz semiconductor heterostructure laser, Nature (London) 417, 156–159 (2002),
https://doi.org/10.1038/417156a
[5] A. Acharyya and J.P. Banerjee, Prospects of IMPATT devices based on wide bandgap semiconductors as potential terahertz source, Appl. Nanosci. 4, 1 (2014),
https://doi.org/10.1007/s13204-012-0172-y
[6] H. Eisele and G.I. Haddad, Two-terminal millimeter-wave sources, in: Proceedings of the Topical Symposium on Millimeter Waves (IEEE, 1997),
https://doi.org/10.1109/TSMW.1997.702438
[7] R.V. Mickevičius, J. Pozela, and A. Reklaitis, Theoretical investigation of impact-ionized plasma instability in GaAs, in: Proceedings of the 8th International Conference on Infrared and Millimeter Waves (IEEE, 1983),
https://doi.org/10.1109/IRMM.1983.9126429
[8] A. Namajūnas, A. Tamaševičius, G. Mykolaitis, S. Bumelienė and J. Požela, Microplasma noise stimulated by microwave electric field, Acta Phys. Pol. A 107, 369 (2005),
https://doi.org/10.12693/APhysPolA.107.369
[9] K.J. Chen, O. Häberlen, A. Lidow, C.I. Tsai, T. Ueda, and Y. Uemoto, GaN-on-Si power technology: devices and applications, IEEE Trans. Electon. Dev. 64, 779 (2017),
https://doi.org/10.1109/TED.2017.2657579
[10] Y. Dai, Y. Li, L. Gao, J. Zuo, B. Zhang, C. Chen, Z. Wang, and W. Zhao, AlGaN/GaN bilateral IMPATT device by two-dimensional electron gas for terahertz application, J. Appl. Phys. 135, 154502 (2024),
https://doi.org/10.1063/5.0196188
[11] E. Alekseev and D. Pavlidis, Large-signal microwave performance of GaN-based NDR diode oscillators fundamental frequency in the range of 0.3–0.4 THz with reliable characteristics, Solid State Electron. 44, 941–947 (2000),
https://doi.org/10.1016/S0038-1101(00)00011-3
[12] A. Iñiguez-de-la-Torre, I. Iñiguez-de-la-Torre, J. Mateos, T. Gonzalez, P. Sangare, M. Faucher, B. Grimbert, V. Brandli, G. Ducournau, and C. Gaquiere, Searching for THz Gunn oscillations in GaN planar nanodiodes, J. Appl. Phys. 111, 113705 (2012),
https://doi.org/10.1063/1.4724350
[13] A.S. Hajo, O. Yilmazoglu, A. Dadgar, F. Küppers, and T. Kusserow, Reliable GaN-based THz Gunn diodes with side-contact and field-plate technologies, IEEE Access 8, 84116 (2020),
https://doi.org/10.1109/ACCESS.2020.2991309
[14] S. Ašmontas, Study of electron heating by nonuniform electric fields in n-Si, Phys. Status Solidi A 31, 409–415 (1975),
https://doi.org/10.1002/pssa.2210310208
[15] S. Ašmontas, J. Požela, and K. Repšas, Investigation of I–V characteristics of Ge and Si asymmetrically necked samples, Liet. Fiz. Rinkinys 15, 249–258 (1975)
[16] A. Sužiedėlis, S. Ašmontas, J. Gradauskas, G. Valušis, and H.G. Roskos, Giga- and terahertz frequency band detector based on an asymmetrically-necked n–n+-GaAs planar structure, J. Appl. Phys. 93, 3034–3038, (2003),
https://doi.org/10.1063/1.1536024
[17] D. Seliuta, I. Kašalynas, V. Tamošiunas, S. Balakauskas, Z. Martūnas, S. Ašmontas, G. Valušis, A. Lisauskas, H.G. Roskos, and K. Köhler, Silicon lens-coupled bow-tie InGaAs-based broadband terahertz sensor operating at room temperature, Electron. Lett. 42, 825–827 (2006),
https://doi.org/10.1049/el:20061224
[18] I. Kašalynas, R. Venckevičius, D. Seliuta, I. Grigelionis, and G. Valušis, InGaAs-based bow-tie diode for spectroscopic terahertz imaging, J. Appl. Phys. 110, 114505 (2011),
https://doi.org/10.1063/1.3658017
[19] I. Kašalynas, R. Venckevičius, and G. Valušis, Continuous wave spectroscopic terahertz imaging with InGaAs-based bow-tie diodes at room temperature, IEEE Sensors, 13, 50–54 (2013),
https://doi.org/10.1109/JSEN.2012.2223459
[20] S. Ašmontas, M. Anbinderis, A. Čerškus, J. Gradauskas, A. Sužiedėlis, A. Šilėnas, E. Širmulis, and V. Umansky, Gated bow-tie diode for microwave to sub-terahertz detection, Sensors 20, 829 (2020),
https://doi.org/10.3390/s20030829
[21] I. Kašalynas, D. Seliuta, R. Simniškis, V. Tamošiunas, K. Köhler, and G. Valušis, Terahertz imaging with bow-tie InGaAs-based diode with broken symmetry, Electron. Lett. 45, 833–835 (2009),
https://doi.org/10.1049/el.2009.0336
[22] L. Minkevičius, V. Tamošiunas, I. Kašalynas, D. Seliuta, G. Valušis, A. Lisauskas, S. Boppel, H.G. Roskos, and K. Köhler, Terahertz heterodyne imaging with InGaAs-based bow-tie diodes, Appl. Phys. Lett. 99, 131101 (2011),
https://doi.org/10.1063/1.3641907
[23] J. Jorudas, D. Seliuta, L. Minkevičius, V. Janonis, L. Subačius, D. Pashnev, S. Pralgauskaitė, J. Matukas, K. Ikamas, A. Lisauskas, E. Šermukšnis, A. Šimukovič, J. Liberis, V. Kovalevskij, and I. Kašalynas, Terahertz bow-tie diode based on asymmetrically shaped AlGaN/GaN heterostructures, Lith. J. Phys. 63, 191–201 (2023),
https://doi.org/10.3952/physics.2023.63.4.1
[24] L. Minkevičius, V. Tamošiūnas, K. Madeikis, B. Voisiat, I. Kašalynas, and G. Valušis, On-chip integration of laser-ablated zone plates for detection enhancement of InGaAs bow-tie terahertz detectors, Electron. Lett. 50, 1367–1369 (2014),
https://doi.org/10.1049/el.2014.1893
[25] R. Ivaškevičiūtė-Povilauskienė, P. Kizevičius, E. Nacius, D. Jokubauskis, K. Ikamas, A. Lisauskas, N. Alexeeva, I. Matulaitienė, V. Jukna, S. Orlov, L. Minkevičius and G. Valušis, Terahertz structured light: nonparaxial Airy imaging using silicon diffractive optics, Light Sci. Appl. 11, 326, 13 (2022),
https://doi.org/10.1038/s41377-022-01007-z
[26] S. Orlov, K. Stanaitis, P. Kizevičius, P. Šlevas, E. Nacius, L. Minkevičius, and G. Valušis, Single-pixel terahertz imaging with enhanced edge detection using angular momentum of structured light, APL Photon. 10, 050805 (2025),
https://doi.org/10.1063/5.0255550
[27] S. Orlov, R. Ivaškevičiūtė-Povilauskienė, K. Mundrys, P. Kizevičius, E. Nacius, D. Jokubauskis, K. Ikamas, A. Lisauskas, L. Minkevičius, and G. Valušis, Light engineering and silicon diffractive optics assisted nonparaxial terahertz imaging, Laser Photonics Rev. 18, 2301197 (2024),
https://doi.org/10.1002/lpor.202301197
[28] T. Ando, A.B. Fowler, and F. Stern, Rev. Electronic properties of two-dimensional systems, Mod. Phys. 54, 437 (1982),
https://doi.org/10.1103/RevModPhys.54.437
[29] J. Požela and B. Pamplin, Plasma and Current Instabilities in Semiconductors, International Series in the Science of the Solid State (Elsevier Science, Burlington, 1981),
https://doi.org/10.1016/C2013-0-05933-6
[30] S.J. Allen Jr., D.C. Tsui, and R.A. Logan, Observation of the two-dimensional plasmon in silicon inversion layers, Phys. Rev. Lett. 38, 980 (1977),
https://doi.org/10.1103/PhysRevLett.38.980
[31] G. Valušis, A. Lisauskas, H. Yuan, W. Knap, and H.G. Roskos, Roadmap of terahertz imaging 2021, Sensors 21, 4092 (2021),
https://doi.org/10.3390/s21124092
[32] M. Dyakonov and M.S. Shur, Detection, mixing and frequency multiplication of terahertz radiation by two-dimentional electronic fluid, IEEE Trans. Electron Devices 43, 380–387 (1996),
https://doi.org/10.1109/16.485650
[33] A. Lisauskas, U. Pfeiffer, E. Öjefors, P.H. Bolívar, D. Glaab, and H.G. Roskos, Rational design of high-responsivity detectors of terahertz radiation based on distributed self-mixing in silicon field-effect transistors, J. Appl. Phys. 105, 114511 (2009),
https://doi.org/10.1063/1.3140611
[34] E. Javadi, D.B. But, K. Ikamas, J. Zdanevičius, W. Knap, and A. Lisauskas, Sensitivity of field-effect transistor-based terahertz detectors, Sensors 21, 2909 (2021),
https://doi.org/10.3390/s21092909
[35] R. Al Hadi, H. Sherry, J. Grzyb, Y. Zhao, W. Forster, H.M. Keller, A. Cathelin, A. Kaiser, and U.R. Pfeiffer, A 1 k-pixel video camera for 0.7–1.1 THz imaging applications in 65-nm CMOS, IEEE J. Solid-State Circuits 47, 2999–3012 (2012),
https://doi.org/10.1109/JSSC.2012.2217851
[36] J. Holstein, N.K. North, M.D. Horbury, S. Kondawar, I. Kundu, M. Salih, A. Krysl, L. Li, E.H. Linfield, J.R. Freeman, A. Valavanis, A. Lisauskas, and H.G. Roskos, 8 × 8 patch-antenna-coupled TeraFET detector array for terahertz quantum-cascade-laser applications, IEEE Trans. THz Sci. Technol. 99, 1–11 (2024),
https://doi.org/10.1109/TTHZ.2024.3438429
[37] A. Soltani, F. Kuschewski, M. Bonmann, A. Generalov, A. Vorobiev, F. Ludwig, M.M. Wiecha, D. Čibiraitė, F. Walla, S. Winnerl, S.C. Kehr, L.M. Eng, J. Stake, and H.G. Roskos, Direct nanoscopic observation of plasma waves in the channel of a graphene field-effect transistor, Light Sci. Appl. 9, 97 (2020),
https://doi.org/10.1038/s41377-020-0321-0
[38] S. Regensburger, M. Mittendorff, S. Winnerl, H. Lu, A.C. Gossard, and S. Preu, Broadband THz detection from 0.1 to 22 THz with large area field-effect transistors, Opt. Express 16, 20733–20741 (2015),
https://doi.org/10.1364/oe.23.020732
[39] J. Schneider, Stimulated emission of radiation by relativistic electrons in a magnetic field, Phys. Rev. Lett. 2, 504 (1959),
https://doi.org/10.1103/PhysRevLett.2.504
[40] P.A. Wolff, Proposal for a cyclotron resonance maser in InSb, Physics (N.Y.) 1, 147 (1964),
https://doi.org/10.1103/PhysicsPhysiqueFizika.1.147
[41] E. Gornik, Recombination radiation from impact-ionized shallow donors in 𝑛-type InSb, Phys. Rev. Lett. 29, 595 (1972),
https://doi.org/10.1103/PhysRevLett.29.595
[42] S. Komiyama, T. Kurosawa, and T. Masumi, Streaming motion of carriers in crossed electric and magnetic fields, in: Hot-Electron Transport in Semiconductors, Topics in Applied Physics, Vol. 58, ed. L. Reggiani (Springer-Verlag,1985) pp. 177–199,
https://doi.org/10.1007/3-540-13321-6_6
[43] Yu. Ivanov and Yu. Vasiljev, Stimulated Landau level emission in p-Ge, Sov. Tech. Phys. Lett. 9, 264 (1983)
[44] E. Gornik and G. Strasser, Landau level laser, Nat. Photon. 15, 875 (2021),
https://doi.org/10.1038/s41566-021-00879-8
[45] D.B. But, M. Mittendorff, C. Consejo, F. Teppe, N.N. Mikhailov, S.A. Dvoretskii, C. Faugeras, S. Winnerl, M. Helm, W. Knap, M. Potemski, and M. Orlita, Suppressed Auger scattering and tunable light emission of Landau-quantized massless Kane electrons, Nat. Photonics 13, 783–787 (2019),
https://doi.org/10.1038/s41566-019-0496-1
[46] J. Pan, Z. Wang, Y. Meng, X. Fu, Y. Shen, and Q. Liu, Photonic Landau levels in an astigmatic frequency-degenerate laser, Commun. Phys. 8, 111 (2025),
https://doi.org/10.1038/s42005-025-02013-4
[47] B.D. Josephson, Possible new effects in superconducting tunneling, Phys. Lett. 1, 251–253 (1962),
https://doi.org/10.1016/0031-9163(62)91369-0
[48] U. Welp, K. Kadowaki, and R. Kleiner, Superconducting emitters of THz radiation, Nat. Photon. 7, 702–710 (2013),
https://doi.org/10.1038/nphoton.2013.216
[49] T. Van Duzer, and C.W. Turner, Principles of Superconductive Devices and Circuits (Elsevier, 1981),
https://doi.org/10.1088/0031-9112/33/2/040
[50] L. Ozyuzer, A.E. Koshelev, C. Kurter, N. Gopalsami, Q. Li, M. Tachiki, K. Kadowaki, T. Yamamoto, H. Minami, H. Yamaguchi, T. Tachiki, K.E. Gray, W.-K. Kwok, and U. Welp, Emission of coherent THz radiation from superconductors, Science 318, 1291–1293 (2007),
https://doi.org/10.1126/science.1149802
[51] I. Kakeya and H. Wang, Terahertz-wave emission from Bi2212 intrinsic Josephson junctions: A review on recent progress, Supercond. Sci. Technol. 29, 073001 (2016),
https://doi.org/10.1088/0953-2048/29/7/073001
[52] M. Zhang, Sh. Nakagawa, Y. Enomoto, Y. Kuzumi, R. Kikuchi, Y. Yamauchi, T. Hattori, R. A. Klemm, K. Kadowaki, T. Kashiwagi, and K. Delfanazari, Tunable terahertz source on a chip with decade-long stability using layered-superconductor elliptical microcavities, Phys. Rev. Appl. 24, 054012 (2025),
https://doi.org/10.1103/pwlx-4sjf
[53] D.T. Young and J.C. Irvin, Millimeter frequency conversion using Au-n-type GaAs Schottky barrier epitaxial diodes with a novel contacting technique, Proc. IEEE 53, 2130–2131 (1965),
https://doi.org/10.1109/PROC.1965.4511
[54] W. Bishop, K. McKinney, R. Mattauch, T. Crowe, and G. Green, A novel whiskerless Schottky diode for millimeter and submillimeter wave application, in: IEEE MTT-S International Microwave Symposium Digest, Vol. 2 (IEEE, 1987) pp. 607–610,
https://doi.org/10.1109/MWSYM.1987.1132483
[55] W. Bishop, E. Meiburg, R. Mattauch, T. Crowe, and L. Poli, A micron-thickness, planar Schottky diode chip for terahertz applications with theoretical minimum parasitic capacitance, in: IEEE MTT-S International Microwave Symposium Digest, Vol. 3, (IEEE, 1990) pp. 1305–1308,
https://doi.org/10.1109/MWSYM.1990.99818
[56] D.W. Porterfield, High-efficiency terahertz frequency triplers, in: Proceedings of 2007 IEEE/MTT-S International Microwave Symposium (IEEE, 2007) pp. 337–340,
https://doi.org/10.1109/MWSYM.2007.380439
[57] P.H. Siegel, R.P. Smith, S.C. Martin, and M.C. Gaidis, THz GaAs monolithic membrane-diode mixer, IEEE Trans. Microw. Theory Techn. 47, 596–604 (1999),
https://doi.org/10.1109/22.763161
[58] J.C. Pearson, B.J. Drouin, A. Maestrini, I. Mehdi, J. Ward, R.H. Lin, S. Yu, J.J. Gill, B. Thomas, C. Lee, G. Chattopadhyay, E. Schlecht, F.W. Maiwald, P.F. Goldsmith, and P. Siegel, Demonstration of a room temperature 2.48–2.75 THz coherent spectroscopy source, Rev. Sci. Instrum. 82, 093105 (2011),
https://doi.org/10.1063/1.3617420
[59] A. Maestrini, J.S. Ward, C. Tripon-Canseliet, J.J. Gill, C. Lee, H. Javadi, G. Chattopadhyay, and I. Mehdi, In-phase power-combined frequency triplers at 300 GHz, IEEE Microwave Wireless Compon. Lett. 18, 218–220 (2008),
https://doi.org/10.1109/LMWC.2008.916820
[60] A. Maestrini, J.S. Ward, J.J. Gill, C. Lee, B. Thomas, R.H. Lin, G. Chattopadhyay, and I. Mehdi, A frequency-multiplied source with more than 1 mW of power across the 840–900 GHz band, IEEE-MTT 58, 1925–1932 (2010),
https://doi.org/10.1109/TMTT.2010.2050171
[61] S. Liang, X. Song, L. Zhang, Y. Lv, Y. Wang, B. Wei, Y. Guo, G. Gu, B. Wang, S. Cai, and Z. Feng, A 177–183 GHz high-power GaN-based frequency doubler with over 200 mW output power, IEEE Electron Device Lett. 41, 669–672 (2020),
https://doi.org/10.1109/LED.2020.2981939
[62] G. Di Gioia, E. Frayssinet, M. Samnouni, V. Chinni, P. Mondal, J. Treuttel, X. Wallart, M. Zegaoui, G. Ducournau, Y. Roelens, Y. Cordier, and M. Zaknoune, High breakdown voltage GaN Schottky diodes for THz frequency multipliers, J. Electron. Mater. 52, 5249–5255 (2023),
https://doi.org/10.1007/s11664-023-10499-3
[63] T. Inoue, M. De Zoysa, T. Asano, and S. Noda, Realization of narrowband thermal emission with optical nanostructures, Optica 2, 27–35 (2015),
https://doi.org/10.1364/OPTICA.2.000027
[64] J. Siegel, S. Kim, M. Fortman, C. Wan, M.A. Kats, P.W. Hon, L. Sweatlock, M.S. Jang, and M.S.V.W. Brar, Electrostatic steering of thermal emission with active metasurface control of delocalized modes, Nat. Commun. 15, 3376 (2024),
https://doi.org/10.5281/zenodo.10615359
https://doi.org/10.1038/s41467-024-47229-0
[65] J. Meléndez, A.J. de Castro, F. López, and J. Meneses, Spectrally selective gas cell for electrooptical infrared compact multigas sensor, Sens. Actuators A 47, 417–421 (1995),
https://doi.org/10.1016/0924-4247(94)00933-9
[66] J. Hodgkinson and R.P. Tatam, Optical gas sensing: A review, Meas. Sci. Technol. 24, 012004 (2013),
https://doi.org/10.1088/0957-0233/24/1/012004
[67] V. Rinnerbauer, Y.X. Yeng, W.R. Chan, J.J. Senkevich, J.D. Joannopoulos, M. Soljačić, and I. Celanovic, High-temperature stability and selective thermal emission of polycrystalline tantalum photonic crystals, Opt. Express 21, 11482–11491 (2013),
https://doi.org/10.1364/OE.21.011482
[68] S. Maruyama, T. Kashiwa, H. Yugami, and M. Esashi, Thermal radiation from two-dimensionally confined modes in microcavities, Appl. Phys. Lett. 79, 1393–1395 (2001),
https://doi.org/10.1063/1.1397759
[69] J. Požela, E. Širmulis, K. Požela, A. Šilėnas, and V. Jucienė, New type of 5–22 THz radiation sources based on semiconductor resonant reflectors, Phys. Status Solidi C 9, 1696–1698 (2012),
https://doi.org/10.1002/pssc.201100641
[70] J.-J.J.-J. Greffet, R. Carminati, K. Joulain, J.-P.J.-P. Mulet, S. Mainguy, and Y. Chen, Coherent emission of light by thermal sources, Nature 416, 61–64 (2002),
https://doi.org/10.1038/416061a
[71] M. Geiser, G. Scalari, F. Castellano, M. Beck, and J. Faist, Room temperature terahertz polariton emitter, Appl. Phys. Lett. 101, 141118 (2012),
https://doi.org/10.1063/1.4757611
[72] V. Janonis, S. Tumėnas, P. Prystawko, J. Kacperski, and I. Kašalynas, Investigation of n-type gallium nitride grating for applications in coherent thermal sources, Appl. Phys. Lett. 116, 112103 (2020),
https://doi.org/10.1063/1.5143220
[73] K. Požela, E. Širmulis, I. Kašalynas, A. Šilėnas, emission from GaAs and AlGaAs, Appl. Phys. Lett. 105, 091501 (2014),
https://doi.org/10.1063/1.4894539
[74] V. Janonis, R.M. Balagula, I. Grigelionis, P. Prystawko, and I. Kašalynas, Spatial coherence of hybrid surface plasmon-phonon-polaritons in shallow n-GaN surface-relief gratings, Opt. Express 29, 13839–13851 (2021),
https://doi.org/10.1364/OE.423397
[75] F. Alves, B. Kearney, D. Grbovic, and G. Karunasiri, Narrowband terahertz emitters using metamaterial films, Opt. Express 20, 21025–21032 (2012),
https://doi.org/10.1364/OE.20.021025
[76] I. Grigelionis, V. Čižas, M. Karaliūnas, V. Jakštas, K. Ikamas, A. Urbanowicz, M. Treideris, A. Bičiūnas, D. Jokubauskis, R. Butkutė, and L. Minkevičius, Narrowband thermal terahertz emission from homoepitaxial GaAs structures coupled with Ti/Au metasurface, Sensors 23, 4600 (2023),
https://doi.org/10.3390/s23104600
[77] V. Čižas, I. Grigelionis, K. Ikamas, V. Jakštas, B. Škėlaitė, D. Jokubauskis, A. Bičiūnas, A. Urbanowicz, M. Treideris, R. Butkutė, and L. Minkevičius, Polarization selective dual frequency metasurface-based resonant thermal terahertz emitters on n-GaAs/GaAs, in: Proceedings of 2023 48th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) (IEEE, 2023) pp. 1–2,
https://doi.org/10.1109/IRMMW-THz57677.2023.10299004
[78] B. Škėlaitė, V. Cižas, K. Ikamas, V. Jakštas, D. Jokubauskis, A. Bičiūnas, A. Urbanowicz, M. Treideris, R. Butkutė, L. Minkevičius, and I. Grigelionis, Comparison of spectral properties of semiconductor structures equipped with metallic (Ti/Au) or n-type GaAs metasurfaces, in: Proceedings of 67th International Open Readings Conference for Students of Physics and Natural Sciences (Vilnius University Press, 2024) p. 167,
https://doi.org/10.15388/Proceedings.2024.46
[79] V. Janonis, D. Pashnev, I. Grigelionis, V.V. Korotyeyev, R.M. Balagula, L. Minkevičius, J. Jorudas, N.V. Alexeeva, L. Subačius, G. Valušis, and I. Kašalynas, Electrically-pumped THz emitters based on plasma waves excitation in III-nitride structures, Proc. SPIE 11499, 8 (2020),
https://doi.org/10.1117/12.2569261
[80] J.J. Ibanes, M.H. Balgos, R. Jaculbia, A. Salvador, A. Somintac, E. Estacio, C.T. Que, S. Tsuzuki, K. Yamamoto, and M. Tan, Terahertz emission from GaAs-AlGaAs core-shell nanowires on Si (100) substrate: Effects of applied magnetic field and excitation wavelength, Appl. Phys. Lett. 102, 063101 (2013),
https://doi.org/10.1063/1.4791570
[81] V. Jakštas, I. Grigelionis, V. Janonis, G. Valušis, I. Kašalynas, G. Seniutinas, S. Juodkazis, P. Prystawko, and M. Leszczyński, Electrically driven terahertz radiation of 2DEG plasmons in AlGaN/GaN structures at 110 K temperature, Appl. Phys. Lett. 110, 202101 (2017),
https://doi.org/10.1063/1.4983286
[82] V.A. Shalygin, M.D. Moldavskaya, M. Ya. Vinnichenko, K.V. Maremyanin, A.A. Artemyev, V.Yu. Panevin, L.E. Vorobjev, D.A. Firsov, V.V. Korotyeyev, A.V. Sakharov, E.E. Zavarin, D.S. Arteev, W.V. Lundin, A.F. Tsatsulnikov, S. Suihkonen, and C. Kauppinen, Selective terahertz emission due to electrically excited 2D plasmons in AlGaN/GaN heterostructure, J. Appl. Phys. 126(18), 183104 (2019),
https://doi.org/10.1063/1.5118771
[83] D. Pashnev, V.V. Korotyeyev, J. Jorudas, T. Kaplas, V. Janonis, A. Urbanowicz, and I. Kašalynas, Experimental evidence of temperature dependent effective mass in AlGaN/GaN heterostructures observed via THz spectroscopy of 2D plasmons, Appl. Phys. Lett. 117, 162101 (2020),
https://doi.org/10.1063/5.0022600
[84] S. Chen, S. Duan, Y. Zou, S. Zhou, J. Wu, B. Jin, H. Zhu, W. Che, and Q. Xue, A 2DEG‐based GaN‐on‐Si terahertz modulator with multi‐mode switchable control, Adv. Opt. Mater. 12, 2401873 (2024),
https://doi.org/10.1002/adom.202401873
[85] K.R. Dzhikirba, A. Shuvaev, D. Khudaiberdiev, I.V. Kukushkin, and V.M. Muravev, Demonstration of the plasmonic THz phase shifter at room temperature, Appl. Phys. Lett. 123, 052104 (2023),
https://doi.org/10.1063/5.0160612
[86] P. Sai, V.V. Korotyeyev, M. Dub, M. Słowikowski, M. Filipiak, D.B. But, Yu. Ivonyak, M. Sakowicz, Yu.M. Lyaschuk, S.M. Kukhtaruk, G. Cywiński, and W. Knap, Electrical tuning of terahertz plasmonic crystal phases, Phys. Rev. X 13, 041003 (2023),
https://doi.org/10.1103/PhysRevX.13.041003
[87] J. Kolodzey and J.P. Gupta, Terahertz emitters based on intracenter transitions in semiconductors, Proc. SPIE 8846, 88460E (2013),
https://doi.org/10.1117/12.2024447
[88] V.A. Shalygin, L.E. Vorobjev, D.A. Firsov, V. Yu. Panevin, A.N. Sofronov, G.A. Melentyev, A.V. Antonov, V.I. Gavrilenko, A.V. Andrianov, A.O. Zakharyin, S. Suihkonen, P.T. Törma, M. Ali, and H. Lipsanen, Impurity breakdown and terahertz luminescence in n-GaN epilayers under external electric field, J. Appl. Phys. 106, 123523 (2009),
https://doi.org/10.1063/1.3272019
[89] I. Grigelionis, V. Jakštas, V. Janonis, I. Kašalynas, P. Prystawko, P. Kruszewski, and M. Leszczynski, Terahertz electroluminescence of shallow impurities in AlGaN/GaN heterostructures at temperatures above 80 K, Phys. Status Solidi B 255, 1700421 (2018),
https://doi.org/10.1002/pssb.201700421
[90] I. Grigelionis, J. Jorudas, V. Jakštas, V. Janonis, I. Kašalynas, P. Prystawko, P. Kruszewski, and M. Leszczyński, Terahertz electroluminescence of shallow impurities in AlGaN/GaN heterostructures at 20 K and 110 K temperature, Mater. Sci. Semicond. Process 93, 280–283 (2019),
https://doi.org/10.1016/j.mssp.2019.01.005
[91] T. Low, A. Chaves, J.D. Caldwell, A. Kumar, N.X. Fang, P. Avouris, T.F. Heinz, F. Guinea, L. Martin-Moreno, and F. Koppens, Polaritons in layered two-dimensional materials, Nat. Mater. 16, 182–194 (2017),
https://doi.org/10.1038/nmat4792
[92] J.D. Caldwell, L. Lindsay, V. Giannini, I. Vurgaftman, T.L. Reinecke, S.A. Maier, and O. J. Glembocki, Low-loss, infrared and terahertz nanophotonics using surface phonon polaritons, Nanophotonics 4, 44–68 (2015),
https://doi.org/10.1515/nanoph-2014-0003
[93] V. Janonis, S. Tumėnas, P. Prystawko, J. Kacperski, and I. Kašalynas, Investigation of n-type gallium nitride grating for applications in coherent thermal sources, Appl. Phys. Lett. 116, 112103 (2020),
https://doi.org/10.1063/1.5143220
[94] C. Walther, M. Fischer, G. Scalari, R. Terazzi, Ni. Hoyler, and J. Faist, Quantum cascade lasers operating from 1.2 to 1.6 THz, Appl. Phys. Lett. 91, 131122 (2007),
https://doi.org/10.1063/1.2793177
[95] M.S. Vitiello and P. De Natale, Terahertz quantum cascade lasers as enabling quantum technology, Adv. Quantum Tech. 5, 2100082 (2022),
https://doi.org/10.1002/qute.202100082
[96] A. Khalatpour, A.K. Paulsen, C. Deimert, Z.R. Wasilewski, and Q. Hu, High-power portable terahertz laser systems, Nat. Photon. 15, 16–20 (2021),
https://doi.org/10.1038/s41566-020-00707-5
[97] A. Khalatpour, M.C. Tam, S.J. Addamane, J. Reno, Z. Wasilewski, and Q. Hu, Enhanced operating temperature in terahertz quantum cascade lasers based on direct phonon depopulation, Appl. Phys. Lett. 122, 161101 (2023),
https://doi.org/10.1063/5.0144705
[98] M. Shahili, S.J. Addamane, A.D. Kim, Ch.A. Curwen, J.H. Kawamura, and B.S. Williams, Continuous-wave GaAs/AlGaAs quantum cascade laser at 5.7 THz, Nanophotonics 13, 1735–1743 (2024),
https://doi.org/10.1515/nanoph-2023-0726
[99] M. Asada and S. Suzuki, Terahertz emitter using resonant-tunneling diode and applications, Sensors 21, 1384 (2021),
https://doi.org/10.3390/s21041384
[100] T. Maekawa, H. Kanaya, S. Suzuki, and M. Asada, Oscillation up to 1.92 THz in resonant tunneling diode by reduced conduction loss, Appl. Phys. Express 9, 024101 (2016),
https://doi.org/10.7567/APEX.9.024101
[101] K. Kasagi, S. Suzuki, and M. Asada, Large-scale array of resonant-tunneling-diode terahertz oscillators for high output power at 1 THz, J. Appl. Phys. 125, 151601 (2019),
https://doi.org/10.1063/1.5051007
[102] S. Kitagawa, M. Mizuno, Sh. Saito, K. Ogino, S. Suzuki, and M. Asada, Frequency-tunable resonant-tunneling-diode terahertz oscillators applied to absorbance measurement, J. Appl. Phys. 56, 058002 (2017),
https://doi.org/10.7567/JJAP.56.058002
[103] L. Esaki and R. Tsu, Superlattice and negative differential conductivity in semiconductors, IBM J. Res. Dev. 14, 61 (1970),
https://doi.org/10.1147/rd.141.0061
[104] E.L. Ivchenko and G.E. Pikus, Superlattices and Other Heterostructures: Symmetry and Optical Phenomena, Springer Series in Solid-State Sciences, vol. 110 (Springer Berlin Heidelberg, Berlin, Heidelberg, 1997),
https://doi.org/10.1007/978-3-642-60650-2
[105] K.F. Renk, B.I. Stahl, A. Rogl, T. Janzen, D.G. Pavel’ev, Yu.I. Koshurinov, V. Ustinov, and A. Zhukov, Subterahertz superlattice parametric oscillator, Phys. Rev. Lett. 95, 126801 (2005),
https://doi.org/10.1103/PhysRevLett.95.126801
[106] P.G. Savvidis, B. Kolasa, G. Lee, and S.J. Allen, Resonant crossover of terahertz loss to the gain of a Bloch oscillating InAs/AlSb superlattice, Phys. Rev. Lett. 92, 196802 (2004),
https://doi.org/10.1103/PhysRevLett.92.196802
[107] T. Hyart, N.V. Alexeeva, J. Mattas, and K.N. Alekseev, Terahertz Bloch oscillator with a modulated bias, Phys. Rev. Lett. 102, 140405 (2009),
https://doi.org/10.1103/PhysRevLett.102.140405
[108] T. Hyart, K.N. Alekseev, and E.V. Thuneberg, Bloch gain in dc-ac-driven semiconductor superlattices in the absence of electric domains, Phys. Rev. B 77, 165330 (2008),
https://doi.org/10.1103/PhysRevB.77.165330
[109] V. Čižas, L. Subačius, N.V. Alexeeva, D. Seliuta, T. Hyart, K. Köhler, K.N. Alekseev, and G. Valušis, Observation of the dissipative parametric gain in a GaAs/AlGaAs superlattice, Phys. Rev. Lett. 128, 236802 (2022),
https://doi.org/10.48550/arXiv.2111.07715
https://doi.org/10.1103/PhysRevLett.128.236802
[110] T. Hyart, A.V. Shorokhov, and K.N. Alekseev, Theory of parametric amplification in superlattices, Phys. Rev. Lett. 98, 220404 (2007),
https://doi.org/10.1103/PhysRevLett.98.220404
[111] V. Čižas, N. Alexeeva, K.N. Alekseev, and G. Valušis, Coexistence of Bloch and parametric mechanisms of high-frequency gain in doped superlattices, Nanomaterials 13, 1993 (2023),
https://doi.org/10.3390/nano13131993
[112] V. Čižas, N. Alexeeva, K. Alekseev, and G. Valušis, Sum-frequency generation and amplification processes in semiconductor superlattices, Lith. J. Phys 63, 148 (2023),
https://doi.org/10.3952/physics.2023.63.3.5