CC BY
5Towards closing "terahertz gap" of quantum cascade lasers
A.A. Dubinov1*, D.V. Ushakov2, A.A. Afonenko2, R.A. Khabibullin3
1-Institute for Physics of Microstructures RAS, GSP-105, 603950, Nizhny Novgorod, Russia 2- Belarusian State University, 4 Nezavisimosti Av., 220030, Minsk, Belarus 3- VG. Mokerov Institute of Ultra-High Frequency Semiconductor Electronics RAS, 7/5 Nagornyy Pr., 117105
Moscow, Russia
Over the two decades of their existence, quantum cascade lasers in the terahertz frequency range (THz QCLs) have come a long way from cryogenic devices with relatively low output powers to powerful THz sources with thermoelectric cooling based on Peltier elements [1]. However, there is a frequency range of the "terahertz gap" (6-10.5 THz), where QCLs do not work due to strong phonon absorption in the arsenide-based heterostructures (AllnGaAs) from which they are made.
Heterostructures with GalnP/AlGalnP quantum wells (QWs) are a promising active medium for solving the problem of creating QCLs with an operating frequency range of 6-7 THz, due to their higher optical phonon energies compared to arsenides. For the first time, the temperature dependences of gain and absorption at frequencies of 6.3-6.9 THz were calculated for a QCL based on GalnP/AlGalnP with 2 QWs in a cascade and a double metal waveguide. It has been shown that the maximum operating temperature of such a QCL can reach 108 K [2].
In addition, we have shown that the capabilities of GaAs/AlGaAs QW heterostructures are wider than previously thought. The possibility of creating such a GaAs/AlGaAs QCL design (with suppression of non-radiative recombination) with a double metal waveguide, which provides lasing with a frequency greater than 6 THz at temperatures above 77 K, was investigated. For this purpose, a band QCL design with a lasing frequency of 5.7-6.3 THz and active region based on 4 GaAs/Alo.i4Gao.86As QWs [3].
Also we propose to use HgCdTe as an alternative material for THz QCLs thanks to a lower phonon energy than in arsenide-based semiconductors. HgCdTe-based QCLs operating with a target frequency of 8.3 THz have been theoretically investigated using the balance equation method. We have analyzed the temperature dependence of the peak gain and predicted the maximum operating temperatures of 170 K and 225 K for three- and two-well designs, respectively [4,5].
The results of these studies open the way to the creation of QCLs for operation in the GaAs phonon absorption band, which is inaccessible to existing arsenide-based QCLs.
The work was supported by the Russian Science Foundation, grant # 23-19-00436, https://rscf.ru/project/23 -19-00436/.
[1] A. Khalatpour, A.K. Paulsen, C. Deimert, Z.R. Wasilewski, Q. Hu, High-power portable terahertz laser systems, Nat. Photonics, 15, 1620 (2021).
[2] D.V. Ushakov, A.A. Afonenko, R.A. Khabibullin, M.A. Fadeev, A.A. Dubinov, Phosphides-based terahertz quantum-cascade laser. Phys. Stat. Solidi RRL, 18, 2300392 (2024).
[3] D.V. Ushakov, A.A. Afonenko, An.A. Afonenko, R.A. Khabibullin, M.A. Fadeev, V.I. Gavrilenko, A.A. Dubinov, Feasibility of GaAs/AlGaAs quantum cascade laser operating above 6 THz. J. Appl. Phys., 135, 133108 (2024).
[4] D. Ushakov, A. Afonenko, R. Khabibullin, D. Ponomarev, V. Aleshkin, S. Morozov, A. Dubinov, HgCdTe-based quantum cascade lasers operating in the GaAs phonon Reststrahlen band predicted by the balance equation method. Opt. Exp., 28, 25371-25382 (2020).
[5] A.A. Dubinov, D.V. Ushakov, A.A. Afonenko, R.A. Khabibullin, M.A. Fadeev, S.V. Morozov, Thin active region HgCdTe-based quantum cascade laser with quasi-relativistic dispersion law. Opt. Lett., 47, 5048-5051 (2022).
