# Narrowband Thermal Terahertz Emission from Homoepitaxial GaAs Structures Coupled with Ti/Au Metasurface

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## Abstract

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## 1. Introduction

## 2. Materials and Methods

## 3. Results

## 4. Discussion

## 5. Conclusions

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Acknowledgments

## Conflicts of Interest

## References

- Ferguson, B.; Zhang, X.C. Materials for terahertz science and technology. Nat. Mater.
**2002**, 1, 26. [Google Scholar] [CrossRef] - Mittleman, D.M. Twenty years of terahertz imaging. Opt. Express
**2018**, 26, 9417–9431. [Google Scholar] [CrossRef] - Valušis, G.; Lisauskas, A.; Yuan, H.; Knap, W.; Roskos, H.G. Roadmap of Terahertz Imaging 2021. Sensors
**2021**, 21, 92. [Google Scholar] [CrossRef] - Jepsen, P.; Cooke, D.; Koch, M. Terahertz spectroscopy and imaging—Modern techniques and applications. Laser Photonics Rev.
**2011**, 5, 124–166. [Google Scholar] [CrossRef] - Bauer, M.; Venckevičius, R.; Kašalynas, I.; Boppel, S.; Mundt, M.; Minkevičius, L.; Lisauskas, A.; Valušis, G.; Krozer, V.; Roskos, H.G. Antenna-coupled field-effect transistors for multi-spectral terahertz imaging up to 4.25 THz. Opt. Express
**2014**, 22, 19235–19241. [Google Scholar] [CrossRef] - Kašalynas, I.; Venckevičius, R.; Minkevičius, L.; Sešek, A.; Wahaia, F.; Tamošiūnas, V.; Voisiat, B.; Seliuta, D.; Valušis, G.; Švigelj, A.; et al. Spectroscopic Terahertz Imaging at Room Temperature Employing Microbolometer Terahertz Sensors and Its Application to the Study of Carcinoma Tissues. Sensors
**2016**, 16, 432. [Google Scholar] [CrossRef] - Tamošiūnas, V.; Minkevičius, L.; Bučius, I.; Jokubauskis, D.; Redeckas, K.; Valušis, G. Design and Performance of Extraordinary Low-Cost Compact Terahertz Imaging System Based on Electronic Components and Paraffin Wax Optics. Sensors
**2022**, 22, 8485. [Google Scholar] [CrossRef] - Siemion, A. Terahertz Diffractive Optics—Smart Control over Radiation. J. Infrared Millim. Terahertz Waves
**2019**, 40, 477–499. [Google Scholar] [CrossRef] - Minkevičius, L.; Tamošiūnas, V.; Kojelis, M.; Ža̧sinas, E.; Bukauskas, V.; Šetkus, A.; Butkutė, R.; Kašalynas, I.; Valušis, G. Influence of Field Effects on the Performance of InGaAs-Based Terahertz Radiation Detectors. J. Infrared Millim. Terahertz Waves
**2017**, 38, 689–707. [Google Scholar] [CrossRef] - Ivaškevičiūtė-Povilauskienė, R.; Kizevičius, P.; Nacius, E.; Jokubauskis, D.; Ikamas, K.; Lisauskas, A.; Alexeeva, N.; Matulaitienė, I.; Jukna, V.; Orlov, S.; et al. Terahertz structured light: Nonparaxial Airy imaging using silicon diffractive optics. Light Sci. Appl.
**2022**, 11, 326. [Google Scholar] [CrossRef] - Jokubauskis, D.; Minkevičius, L.; Karaliūnas, M.; Indrišiūnas, S.; Kašalynas, I.; Račiukaitis, G.; Valušis, G. Fibonacci terahertz imaging by silicon diffractive optics. Opt. Lett.
**2018**, 43, 2795. [Google Scholar] [CrossRef] - Han, Z.; Takida, Y.; Ohno, S.; Minamide, H. Terahertz Fresnel-zone-plate thin-film lens based on a high-transmittance double-layer metamaterial phase shifter. Opt. Express
**2022**, 30, 18730. [Google Scholar] [CrossRef] - Jain, R.; Hillger, P.; Ashna, E.; Grzyb, J.; Pfeiffer, U.R. A 64-Pixel 0.42-THz Source SoC with Spatial Modulation Diversity for Computational Imaging. IEEE J. Solid-State Circuits
**2020**, 55, 3281–3293. [Google Scholar] [CrossRef] - Asada, M.; Suzuki, S. Terahertz Emitter Using Resonant-Tunneling Diode and Applications. Sensors
**2021**, 21, 1384. [Google Scholar] [CrossRef] - Lewis, R. A review of terahertz sources. J. Phys. D Appl. Phys.
**2014**, 47, 374001. [Google Scholar] [CrossRef] - Ikamas, K.; But, D.B.; Cesiul, A.; Kołaciński, C.; Lisauskas, T.; Knap, W.; Lisauskas, A. All-Electronic Emitter-Detector Pairs for 250 GHz in Silicon. Sensors
**2021**, 21, 5795. [Google Scholar] [CrossRef] - Maestrini, A.; Ward, J.; Chattopadhyay, G.; Schlecht, E.; Mehdi, I. Terahertz Sources Based on Frequency Multiplication and Their Applications. Frequenz
**2008**, 62, 118–122. [Google Scholar] [CrossRef] - Papaioannou, E.T.; Beigang, R. THz spintronic emitters: A review on achievements and future challenges. Nanophotonics
**2021**, 10, 1243–1257. [Google Scholar] [CrossRef] - Chen, X.; Wang, H.; Liu, H.; Wang, C.; Wei, G.; Fang, C.; Wang, H.; Geng, C.; Liu, S.; Li, P.; et al. Generation and Control of Terahertz Spin Currents in Topology-Induced 2D Ferromagnetic Fe3GeTe2|Bi2Te3 Heterostructures. Adv. Mater.
**2022**, 34, 2106172. [Google Scholar] [CrossRef] - Huang, Y.D.; Yu, Y.; Qin, H.; Sun, J.D.; Zhang, Z.P.; Li, X.X.; Huang, J.J.; Cai, Y. Plasmonic terahertz modulator based on a grating-coupled two-dimensional electron system. Appl. Phys. Lett.
**2016**, 109, 201110. [Google Scholar] [CrossRef] - Hirakawa, K.; Yamanaka, K.; Grayson, M.; Tsui, D.C. Far-infrared emission spectroscopy of hot two-dimensional plasmons in Al0.3Ga0.7As/GaAs heterojunctions. Appl. Phys. Lett.
**1995**, 67, 2326–2328. [Google Scholar] [CrossRef] - Shalygin, V.A.; Moldavskaya, M.D.; Vinnichenko, M.Y.; Maremyanin, K.V.; Artemyev, A.A.; Panevin, V.Y.; Vorobjev, L.E.; Firsov, D.A.; Korotyeyev, V.V.; Sakharov, A.V.; et al. Selective terahertz emission due to electrically excited 2D plasmons in AlGaN/GaN heterostructure. J. Appl. Phys.
**2019**, 126, 183104. [Google Scholar] [CrossRef] - Zhang, X.; Xu, Q.; Xia, L.; Li, Y.; Gu, J.; Tian, Z.; Ouyang, C.; Han, J.; Zhang, W. Terahertz surface plasmonic waves: A review. Adv. Photonics
**2020**, 2, 014001. [Google Scholar] [CrossRef] - Alves, F.; Kearney, B.; Grbovic, D.; Karunasiri, G. Narrowband terahertz emitters using metamaterial films. Opt. Express
**2012**, 20, 21025–21032. [Google Scholar] [CrossRef] - Puscasu, I.; Schaich, W.L. Narrow-band, tunable infrared emission from arrays of microstrip patches. Appl. Phys. Lett.
**2008**, 92, 233102. [Google Scholar] [CrossRef] - Askenazi, B.; Vasanelli, A.; Todorov, Y.; Sakat, E.; Greffet, J.J.; Beaudoin, G.; Sagnes, I.; Sirtori, C. Midinfrared Ultrastrong Light–Matter Coupling for THz Thermal Emission. ACS Photonics
**2017**, 4, 2550–2555. [Google Scholar] [CrossRef] - Ohtani, K.; Turčinková, D.; Bonzon, C.; Benea-Chelmus, I.C.; Beck, M.; Faist, J.; Justen, M.; Graf, U.U.; Mertens, M.; Stutzki, J. High performance 4.7 THz GaAs quantum cascade lasers based on four quantum wells. New J. Phys.
**2016**, 18, 123004. [Google Scholar] [CrossRef] - Arlauskas, A.; Krotkus, A. THz excitation spectra of AIIIBV semiconductors. Semicond. Sci. Technol.
**2012**, 27, 115015. [Google Scholar] [CrossRef] - Pashnev, D.; Korotyeyev, V.V.; Jorudas, J.; Kaplas, T.; Janonis, V.; Urbanowicz, A.; Kašalynas, I. Experimental evidence of temperature dependent effective mass in AlGaN/GaN heterostructures observed via THz spectroscopy of 2D plasmons. Appl. Phys. Lett.
**2020**, 117, 162101. [Google Scholar] [CrossRef] - Fu, C.J.; Zhang, Z.M.; Tanner, D.B. Planar heterogeneous structures for coherent emission of radiation. Opt. Lett.
**2005**, 30, 1873–1875. [Google Scholar] [CrossRef] - Lam, V.D.; Kim, J.B.; Lee, S.J.; Lee, Y.P.; Rhee, J.Y. Dependence of the magnetic-resonance frequency on the cut-wire width of cut-wire pair medium. Opt. Express
**2007**, 15, 16651–16656. [Google Scholar] [CrossRef] - Lee, B.J.; Wang, L.P.; Zhang, Z.M. Coherent thermal emission by excitation of magnetic polaritons between periodic strips and a metallic film. Opt. Express
**2008**, 16, 11328–11336. [Google Scholar] [CrossRef] - Li, T.; Li, J.Q.; Wang, F.M.; Wang, Q.J.; Liu, H.; Zhu, S.N.; Zhu, Y.Y. Exploring magnetic plasmon polaritons in optical transmission through hole arrays perforated in trilayer structures. Appl. Phys. Lett.
**2007**, 90, 251112. [Google Scholar] [CrossRef] - Li, T.; Wang, S.M.; Liu, H.; Li, J.Q.; Wang, F.M.; Zhu, S.N.; Zhang, X. Dispersion of magnetic plasmon polaritons in perforated trilayer metamaterials. J. Appl. Phys.
**2008**, 103, 023104. [Google Scholar] [CrossRef] - Guo, Y.; Shuai, Y.; Zhao, J. Tailoring radiative properties with magnetic polaritons in deep gratings and slit arrays based on structural transformation. J. Quant. Spectrosc. Radiat. Transf.
**2020**, 242, 106788. [Google Scholar] [CrossRef] - Jin, W.; Li, W.; Orenstein, M.; Fan, S. Inverse design of lightweight broadband reflector for relativistic lightsail propulsion. ACS Photonics
**2020**, 7, 2350–2355. [Google Scholar] [CrossRef] - Yao, H.; Snyder, P.G.; Woollam, J.A. Temperature dependence of optical properties of GaAs. J. Appl. Phys.
**1991**, 70, 3261–3267. [Google Scholar] [CrossRef] - Zhou, J.; Economon, E.N.; Koschny, T.; Soukoulis, C.M. Unifying approach to left-handed material design. Opt. Lett.
**2006**, 31, 3620–3622. [Google Scholar] [CrossRef] - Yu, C.; Zhu, H.; Wang, F.; Chang, G.; Zhu, H.; Chen, J.; Chen, P.; Tang, Z.; Lu, W.; Shen, C.; et al. Highly efficient power extraction in terahertz quantum cascade laser via a grating coupler. Appl. Phys. Lett.
**2018**, 113, 121114. [Google Scholar] [CrossRef] - Feiginov, M.; Kanaya, H.; Suzuki, S.; Asada, M. Operation of resonant-tunneling diodes with strong back injection from the collector at frequencies up to 1.46 THz. Appl. Phys. Lett.
**2014**, 104, 243509. [Google Scholar] [CrossRef]

**Figure 1.**(

**a**) Resonant frequency dependency on the period and side length of the metacell. One may note that the resonant frequency is independent of metacell period. This effect exposes the magnetic polariton nature of the observed processes. Emission in the interval from 0.3 THz to 3 THz is available by varying the metacell side length. (

**b**) Power at the resonant frequency dependency on the period and side length of the metacell. One may note that the period has significant control over the power of the thermal metacell emitter at the resonant frequency, determining the importance of proper period selection for the creation of an efficient thermal metamaterial-based emitter. The positions of the white dots represent the parameters of the fabricated thermal emitters.

**Figure 2.**GaAs-based MP excitations sustaining structure that consists of the n-GaAs substrate layer (W), undoped GaAs spacer layer (d), and periodic TiAu metasurface defined by geometrical parameters: the side length $\left(l\right)$ of the square, the period $\left(L\right)$ of metasurface, and metasurface layer height $\left(h\right)$. The inset shows the photo of $l=39$ μm metasurface acquired with the microscope KH-7700 from Hirox (

**a**). The absolute value of simulated magnetic field x component distributions for the first (

**b**) and the third (

**c**) MP harmonics under the square metacell. Arrows denote the direction of the flow of the currents inducing the magnetic field. The blue dash-dotted lines represent metalized surface contours.

**Figure 3.**Resonant frequency dependency on the metacell angle fabrication quality, described as the radius of the rounded corners. A small resonant frequency increase is visible with an increase in the radius. Upper left inset depicts spectral dependencies on the rounded corner angle. One may additionally note a small increase in the absorption with a radius increase. Bottom left inset depicts boundary sweep variations being square ($R=0\phantom{\rule{3.33333pt}{0ex}}\mathsf{\mu}$m), circle $(R=l/2)$, and one of the variations ($R=5\phantom{\rule{3.33333pt}{0ex}}\mathsf{\mu}$m), results of which are highlighted by a black point on the main graph and black bold line on the upper left inset.

**Figure 4.**(

**a**) Reflectance spectra of GaAs-based metasurfaces with different square metacell side lengths (l) at room temperature. Inset: the THz-TDS setup used for reflection measurements. (

**b**) GaAs-based metasurface thermo-emission spectra at 390 °C temperature for different square metacell lengths. Inset: the setup of Fourier spectrometer used for emission spectra measurements.

**Figure 5.**The dependencies of emitted radiation of first MP harmonics on sample rotation angle off the optical axis. Symbols connected with dashed lines denote the different rotation angles: circles—0 deg; squares—8 deg; triangles—23 deg. The solid curve represents the spectrum simulated using the RCWA method. Inset demonstrates the sample orientation during the experiment.

**Figure 6.**Map of reflection resonant frequency dependence on a rectangular metacell side length calculated by RCWA. Symbols denote the resonant frequencies obtained from experimental reflection (diamonds) and emission (circles) results. The solid curves represent theoretically calculated MPs resonant frequency dependence on single metasurface element side length; n denotes the number of the harmonic. The inset shows the $LC$ equivalent circuit used to calculate the theoretical curves.

**Table 1.**Resonant frequency peak values of MPs versus different metacell side lengths estimated in four methods: calculated using the RCWA method, experimentally measured in reflectance configuration, experimentally measured in emission configuration, and calculated using an $LC$ equivalent circuit.

Size, μm | RCWA | Reflectance | Emission | $\mathit{LC}$ |
---|---|---|---|---|

1st harmonic | ||||

42 | 0.74 | 0.74 | 0.71 | 0.76 |

39 | 0.78 | 0.82 | 0.77 | 0.82 |

38 | 0.78 | 0.85 | 0.79 | 0.84 |

26 | 1.13 | 1.32 | 1.22 | 1.23 |

3rd harmonic | ||||

42 | 2.18 | 2.32 | 2.11 | 2.27 |

39 | 2.27 | 2.43 | 2.32 | 2.45 |

38 | 2.31 | 2.51 | 2.32 | 2.52 |

26 | 3.27 | – | – | 3.69 |

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**MDPI and ACS Style**

Grigelionis, I.; Čižas, V.; Karaliūnas, M.; Jakštas, V.; Ikamas, K.; Urbanowicz, A.; Treideris, M.; Bičiūnas, A.; Jokubauskis, D.; Butkutė, R.;
et al. Narrowband Thermal Terahertz Emission from Homoepitaxial GaAs Structures Coupled with Ti/Au Metasurface. *Sensors* **2023**, *23*, 4600.
https://doi.org/10.3390/s23104600

**AMA Style**

Grigelionis I, Čižas V, Karaliūnas M, Jakštas V, Ikamas K, Urbanowicz A, Treideris M, Bičiūnas A, Jokubauskis D, Butkutė R,
et al. Narrowband Thermal Terahertz Emission from Homoepitaxial GaAs Structures Coupled with Ti/Au Metasurface. *Sensors*. 2023; 23(10):4600.
https://doi.org/10.3390/s23104600

**Chicago/Turabian Style**

Grigelionis, Ignas, Vladislovas Čižas, Mindaugas Karaliūnas, Vytautas Jakštas, Kȩstutis Ikamas, Andrzej Urbanowicz, Marius Treideris, Andrius Bičiūnas, Domas Jokubauskis, Renata Butkutė,
and et al. 2023. "Narrowband Thermal Terahertz Emission from Homoepitaxial GaAs Structures Coupled with Ti/Au Metasurface" *Sensors* 23, no. 10: 4600.
https://doi.org/10.3390/s23104600