CC BY
14THz-I-5
Long wavelength stimulated emission in HgTe/CdHgTe quantum well heterostructures
A. Dubinov1,2, V. Gavrilenko1,3, V. Rumyantsev1,3, M. Fadeev1,4, V. Utochkin1, V. Aleshkin1,3, N. Mikhailov5,6, S. Morozov1,2, Z. Krasilnik1,2, C. Sirtori7
institute for Physics of Microstructures RAS, Semiconductor physics department, Nizhny Novgorod, Russian Federation
2Lobachevsky State University, Radiophysics department, Nizhny Novgorod, Russian Federation 3Lobachevsky State University, Advanced School of General and Applied Physics, Nizhny Novgorod, Russian Federation
4L2C, UMR CNRS 5221, Montpellier University, Terahertz Spectroscopy Group, Montpellier, France
5A.V. Rzhanov Institute of Semiconductor Physics, Siberian Branch of Russian Academy of Sciences, Lab #15, Novosibirsk, Russian Federation
6Novosibirsk State University, Physics department, Novosibirsk, Russian Federation 7Laboratoire de Physique de l'Ecole Normale Supérieure, Physique Quantique et Dispositifs QUAD, Paris, France
The development of compact semiconductor far-infrared sources is an important problem of modern physics of semiconductors. Promising candidates are lasers based on HgTe/HgCdTe heterostructures with quantum wells (QWs). HgCdTe has low enough phonon frequencies to enter 5 - 12 THz region, currently unavailable for quantum cascade lasers (QCLs) and allows bandgap tuning down to less than 10 meV (2 THz).
Stimulated emission (SE) under optical pumping was obtained in HgTe/HgCdTe quantum well (QW) heterostructures in the spectral range up to 25 pm for dielectric waveguide and up to 31 pm for "Reststrahlen band mode localization". It was shown that longer pumping wavelengths provide better performance. Under near-IR pumping (Xexc ~ 2.3 pm), we observed quenching of SE from HgTe/CdHgTe QW laser structures as the pumping increased beyond the SE threshold. We attribute this effect to the excessive "heating" of non-equilibrium charge carriers leading to activation of Auger processes (which have a threshold with respect to carrier energy). Switching to mid-IR (Xexc ~ 10.6 pm using CO2-laser) pumping allowed to avoid the SE quenching and resulted into much better output characteristics of the laser structures in the wavelength range from 14 to 20 pm. At shorter wavelengths X ~ 10 pm the excitation threshold power was shown to be as low as 120 W/cm2 and the SE was obtained even at CW excitation (Xexc ~ 0.9 pm). Under low-power cw QCL pumping (Xexc ~ 8 pm) photoluminescence signal was found in HgTe/CdHgTe heterostructures up to 20 pm. These results suggest that it is possible to achieve SE under cw pumping at the wavelengths above 10 pm at higher pumping intensity. HgCdTe heterostructures prove to be a promising candidate for far-IR lasers and optical converters from mid-IR QCLs to far-IR region.
This work was financially supported by the Russian Foundation of the Basic Research (#18-5216013).
