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4The 30th International Conference on Advanced Laser Technologies ALT'23
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LM-I-22
THz quantum cascade lasers with resonant two-photon design
R.A. Khabibullin1'2'3*. D.V. Ushakov4, A.A. Afonenko4, D.S. Ponomarev1, M.A. Ladugin2, A.A. Marmalyuk2, S.V. Morozov5, V.I. Gavrilenko5
1- V.G. Mokerov Institute of ultra-high frequency semiconductor electronics of RAS, Moscow, Russia 2- Moscow Institute of Physics and Technology, Dolgoprudny, Russia 3- Ioffe Institute, St. Petersburg, Russia 4- Belarusian State University, Minsk, Belarus 5- Institute for Physics of Microstructures of RAS, Nizhny Novgorod, Russia
khabibullin@isvch. ru
The scheme of laser transitions of the proposed two-photon design is based on five electron levels. This design works due to electron tunneling from the injector level 1' to the upper laser level 5, two sequential laser transitions (5 - 4 and 4 - 3) with an energy of 14.9 meV (3.6 THz) and depletion of the lower laser level 3 due to tunneling to the extractor level 2 and resonant emission of an optical phonon. In this case, the "intermediate" level 4 simultaneously plays the role of the lower laser level for the first optical transition and the upper laser level for the second optical transition. The operating voltage on one active module is close to the sum of two radiation energies and the energy of a longitudinal optical phonon 2-hro-mz + hroLO.
An optimized two-photon design was developed using the balanced equation method [1,2] and grown by MOVPE technique with 10 p,m active region thickness. The fabricated QCLs with Au-Au double metal waveguide based on grown structures show an excellent growth robustness, as all MOVPE-grown structures (6 wafers) demonstrate laser generation. The maximum operation temperatures of fabricated lasers are equal to 90-100 K. The light-current characteristics have two shoulders in the experimental curves (see Fig. 1), which corresponds to the two-photon nature of the proposed design. The fabricated QCLs have a lasing frequency of 3.6 THz (see Fig. 2), which completely coincides with the target frequency. At high currents the generation shifts to 3.7 THz. This effect can be explained by increasing the energy separation between lasing levels 5-4 (the first THz photon) at high electric fields.
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Fig. 1. Pulsed current-voltage and light-current characteristics of MOVPE-grown THz QCLs with two-photon design.
3,60 3,62 3,64 3,66 3,68 3,70 3,72 3,74 3,76
Frequency, THz
Fig. 2. Emission spectra of MOVPE-grown THz QCLs with two-photon design.
This study was partially supported by the Russian Science Foundation project no. 21-72-30020 and the Ministry of Science and Higher Education of the Russian Federation in the scope of the government assignment (Agreement 075-03-2023-106 13.01.2023).
[1] D. V. Ushakov, A. A. Afonenko, A. A. Dubinov, V. I. Gavrilenko, O. Yu. Volkov, N. V. Shchavruk, D. S. Ponomarev, R. A. Khabibullin, "Balance-equation method for simulating terahertz quantum-cascade lasers using a wave-function basis with reduced dipole moments of tunnelcoupled states," Quantum Electronics, vol. 49, pp. 913-918, (2019).
[2] 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. Express, vol. 28, pp. 25371-25382, (2020).
