Lasing from HgCdTe microdisc cavities is demonstrated at wavelengths as long as 22 — 25 μm. The optical threshold and operation temperature are far from being limited by intrinsic recombination processes. The employed ion etching technology appears to introduce additional defects in the vicinity of the microdiscs, degrading figures of merit as the height of the cavity increases. However, a watt-level mid-infrared pumping source should suffice for lasing in microdiscs with moderate height and ~100 μm diameter.

Гетероструктуры с квантовыми ямами на основе твердых растворов HgCdTe в последнее время рассматриваются как перспективный материал для приложений среднего инфракрасного диапазона, в частности, для создания лазеров. В данной работе исследовано влияние процессов фотолитографии с различными масками и ионного травления на оптические свойства мезаструктур с микродисковыми, микрокольцевыми и гребенчатыми резонаторами, сформированных на основе гетероструктур с квантовыми ямами HgCdTe/CdHgTe. Показана возможность использования предлагаемой технологии для изготовления лазеров диапазона окна прозрачности атмосферы 3 – 5 мкм, работающих при термоэлектрическом охлаждении.

Thanks to the industry of infrared (IR) detectors the quality of Hg(Cd)Te/CdHgTe heterostructures is approaching the quality of their A3B5 counterparts. Hg(Cd)Te/CdHgTe quantum wells (QWs) deliver a widely (from 0 to over 1200 meV) variable bandgap, while maintaining the ability to tailor the carrier energy spectrum. We show that in the long-wavelength part of mid-IR Hg(Cd)Te/CdHgTe QWs offer the quasi-relativistic carrier dispersion law that suppresses the Auger recombination, enabling stimulated emission (SE) up to 31 µm, and laser generation up to 24 µm in the temperature range from 10 to 80 K. The record wavelength of 31 µm (inaccessible for existing cascade lasers) is achieved by a peculiar design of the structure utilizing the reflection of the waveguide mode from the substrate near the Reststrahlen band of GaAs. In the atmospheric transparency window of 3–5 µm, we were able to mitigate not only bulk-like Auger recombination but also QW-specific thresholdless Auger processes associated with non-radiative transitions into barriers. As a result, optically pumped laser action on whispering gallery modes was achieved in the vicinity of 4 µm up to 230 K.

Amplified interband emission within the 14–24 μm range is investigated in HgCdTe-based quantum wells under optical pumping. Carrier lifetimes are shown to be marginally limited only by Shockley–Read–Hall recombination, fully realizing the advantage of relativistic energy spectra of 2D HgCdTe in terms of suppressing the Auger processes. By carefully optimizing the waveguides and mitigating carrier heating, we achieve amplification thresholds as low as 1.5–2 W/cm2 at a pulse duration of 20–500 μs. With last generation quantum cascade lasers used for optical pumping, we estimate that continuous-wave HgCdTe lasers can operate in the very long-wavelength range (15–30 μm) and beyond.

Various designs of dielectric waveguides made of heterostructures with CdHgTe quantum wells grown by molecular beam epitaxy have been studied to generate stimulated emission in the 15–30 μm wavelength range. The reduction of radiation losses in optimized structures has made it possible to reduce the threshold intensity of the generation of stimulated emission to ~100 W/cm 2 . Modernized growth technology has ensured the reduction of the residual cadmium content in HgCdTe quantum wells to 2.5%, which has allowed us to increase the threshold energy of Auger recombination, as well as the maximum temperature for the observation of stimulated emission at interband transitions above 100 K. The results obtained are prerequisites for the implementation of coherent radiation sources exceeding in characteristics of lead–tin chalcogenide lasers used in the 15–30 μm spectral range.

Due to their widely tunable bandgap, HgCdTe heterostructures with quantum wells are a promising material system for semiconductor lasers in the entire mid-infrared range. Recently, Auger-suppressed structures allowed interband stimulated emission (SE) in the atmospheric transparency window 3–5 μm well above 200 K, while previously it was limited to temperatures below 175 K. In contrast to earlier works focused on ridge or vertical emitting HgCdTe lasers, here we demonstrate a whispering gallery mode microdisk (d = 50 μm) laser operating under optical pumping at ∼4 μm in the temperature range attainable by the thermoelectric cooling. Above 200 K, the emission spectrum consists of multiple 0.37-meV-wide peaks associated with the modes of the disk resonator. Laser generation is achieved up to 230 K, which is 40 K lower than the quenching temperature of SE in the unprocessed macroscopic sample. We associate the difference with the optical losses introduced by the inclined walls of the disk.

Thin HgCdTe/CdHgTe quantum wells (QWs) grown on alternative GaAs (013) substrates have been recently proposed as a material for coherent emitters in the mid-IR region. In this work, we develop a technological process for the fabrication of ridge microresonators in waveguide heterostructures with multiple HgCdTe QWs via photolithography and ion etching. We process two samples with different ridge heights and analyze their emission spectra measured under optical excitation. The width of the emission spectra dropped by an order of magnitude compared to the nonprocessed as-grown structure, allowing one to conclude that lasing at 9.2-7.1 µm takes place within the 8-120 K temperature range. However, both samples demonstrated faster temperature quenching of lasing than that of the single-pass stimulated emission from the nonprocessed structure, as well as a drop in the carrier lifetimes. These figures of merit are likely to be compromised not by the Q factor of the cavities, but due to defects induced during the etching process. Finally, the implications for HgCdTe-based lasers for the 3-5 µm transparency window and longer wavelengths (beyond 20 µm) are discussed.

The first results on the study of photoluminescence and lasers radiation spectra of a CdHgTe solid solution-based quantum well structure with microdisk cavities of different diameters are demonstrated. It is shown that the presence of cavities contributes to an increase in the maximum operating temperature of generation compared to the unprocessed structure.

Photoluminescence and laser emission spectra of CdHgTe solid-solution quantum-well structures with microdisk cavities of different diameters are demonstrated. The presence of a cavity is shown to contribute to an increase in the maximum operating temperature of generation as compared to the unprocessed structure.

Heterostructures with thin Hg(Cd)Te/CdHgTe quantum wells (QWs) are attractive for the development of mid-infrared interband lasers. Of particular interest are room-temperature operating emitters for the short-wavelength infrared range (SWIR, typically defined as 1.7–3 μm). In this work, we report on the observation of stimulated emission (SE) in the 2.65–2.75 µm wavelength range at room temperature in an optically pumped HgCdTe QW laser heterostructure. We study a series of three samples with lengths ranging from 2.5 to 7 mm and discuss the effects related to the non-uniformity of the excitation beam profile. SE threshold intensity and the magnitude of pump-induced carrier heating are found to be effectively dependent on the chip size, which should be accounted for in possible designs of HgCdTe-based optical converters. We also pay attention to the problem of active medium engineering in order to push the SE wavelength towards the 3–5 µm atmospheric window and to lower the SE threshold.

Long-wavelength stimulated emission (SE) is studied in optically pumped HgCdTe quantum well heterostructures with dielectric waveguides. Continuous temperature tuning of the wavelength from 27 to 18 μm is achieved in structures with optimized waveguides. Above 27 μm, SE clamps at 31 μm wavelength, where mode leaking is reduced due to the Reststrahlen effect in the GaAs substrate. The operating temperature is mainly limited by the activation of Auger recombination in quasi-equilibrium conditions, while at low temperatures, we expect that lowering initial carrier heating would enhance the gain considerably. We conclude that exploiting the Reststrahlen effect should allow one to achieve continuous wavelength tuning around 30 μm and operating wavelengths up to 40 μm with technologically attainable epistructure thickness.

In recent years, narrow gap heterostructures with Hg1-xCdxTe/CdyHg1-yTe quantum wells have been actively studied both in connection with the topic of topological insulators and from the point of view of their application in optoelectronics in the terahertz domain. In this work, we study the photoconductivity and photoluminescence spectra of structure with a band gap of 40 meV. In addition to interband transitions, the features of the spectra associated with the resonance states of acceptors have been identified. The possibilities of using the structures under study to develop interband emitters at a wavelength of ~30 μm, which is inaccessible to existing quantum-cascade lasers, are discussed. Keywords: narrow-gap semiconductors, HgCdTe, resonance states, acceptors, photoluminescence.

Mercury vacancies, acting as double acceptors, are the dominant point defects in ternary HgCdTe alloys. Though HgCdTe is one of the leading materials in infrared optoelectronics, the energy spectra of the vacancies are still a matter of some debate. This work investigated the rates at which holes are captured to a singly ionized mercury vacancy via acoustic phonon emission in narrow-gap Hg1−xCdxTe with technologically relevant x~0.22. Combined with the calculated rates of intracenter transitions, the data allow one to predict the most pronounced optical transitions in the emission spectrum of a double-charged acceptor. The results are sustained by the photoluminescence spectroscopy in the terahertz domain, allowing one to identify the emission band that is related to neutral vacancies.

In recent years, narrow gap heterostructures with Hg1-xCdxTe/CdyHg1-yTe quantum wells have been actively studied both in connection with the topic of topological insulators and from the point of view of their application in optoelectronics in the terahertz domain. In this work, we study the photoconductivity and photoluminescence spectra of structure with a band gap of 40 meV. In addition to interband transitions, the features of the spectra associated with the resonance states of acceptors have been identified. The possibilities of using the structures under study to develop interband emitters at a wavelength of ~ 30 μm, which is inaccessible to existing quantum-cascade lasers, are discussed.

HgCdTe-based heterostructures with quantum wells (QWs) are a promising material for semiconductor lasers in the atmospheric transparency window (3–5 μm) thanks to the possibility of suppressing Auger recombination due to the no-parabolic law of carrier dispersion. In this work, we analyze the thresholds of stimulated emission (SE) under optical pumping from heterostructures with a different number of QWs in the active region of the structure. Total losses in structures are determined from the comparison of thresholds for the different number of QWs in the active region. It is shown that, thanks to the increased modal gain, a higher number of QWs results in lower threshold pumping intensity and, consequently, higher temperature of SE. These results indicate that improvements to the modal gain can result in a moderate uplift in the temperature of SE from mid-infrared HgCdTe-based heterostructures. On the other hand, at a high enough QW count threshold, the intensity no longer depends on the number of the QWs and is determined by the transparency concentration of a single QW.

The generation of the second-harmonic radiation of a gyrotron with an operating frequency of 263 GHz due to second-order lattice nonlinearity in iron-doped indium-phosphide crystals is experimentally demonstrated. It is shown that second-harmonic radiation can be used in the magnetospectroscopy of semiconductor nanostructures. The possibility of generating the difference frequency in these crystals excited by two mid-IR sources with close wavelengths is discussed.

Abstract. Temperature-driven photoconductivity spectra are studied in HgCdTe thin films and quantum well (QW) heterostructures grown by molecular beam epitaxy (MBE). It is shown that the absorption edge steepness in narrow gap HgCdTe epilayers approaches the fundamental limit. The corresponding Urbach energy is 1.5 to 4 meV at 4.2 to 77 K, which is an order of magnitude lower than values reported previously, indicating a significant progress in the quality of structures grown by MBE. Auger-suppressed multi-QW heterostructures that can be used for development of long-wavelength lasers/detectors are shown to have the comparable steepness of the absorption edge. The corresponding “Urbach” energy is much less than the threshold energy of the Auger recombination, which means that furthering the operating wavelengths beyond 20  μm is feasible for optoelectronic devices based on HgCdTe structures.

We consider the GaAsP/AlGaAs/GaAs laser design with two different quantum wells for simultaneous generation of ${{\rm{TE}}_0}$ and ${{\rm{TM}}_0}$ modes having different frequencies in near-IR range. We theoretically investigate the possibility of effective difference frequency generation in the 7.5-8 and 10.5-11 THz regions in the laser design proposed. Resonant increase of second-order susceptibility in AlGaAs in these ranges provides sufficient generation efficiency. We demonstrate an output power-conversion factor for the difference frequencies in the 7.5-8 THz range to be up to ${{4 {-} 8}}\;{{\rm{MW}}^{- 1}}$ at room temperature in such a laser.

HgTe/CdHgTe quantum well (QW) heterostructures have attracted a lot of interest recently due to insights they provided towards the physics of topological insulators and massless Dirac fermions. Our work focuses on HgCdTe QWs with the energy spectrum close to the graphene-like relativistic dispersion that is supposed to suppress the non-radiative Auger recombination. We combine various methods such as photoconductivity, photoluminescence and magneto-optical measurements as well as transmission electron microscopy to retrofit growth parameters in multi-QW waveguide structures, designed for long wavelengths lasing in the range of 10–22 μm. The results reveal that the attainable operating temperatures and wavelengths are strongly dependent on Cd content in the QW, since it alters the dominating recombination mechanism of the carriers.

An express technique for characterizing narrow-gap waveguide heterostructures with the HgCdTe/CdHgTe quantum wells is proposed, which is based on an analysis of their room-temperature luminescence response. Advantages and constraints of this characterization technique are discussed in comparison with methods for more detailed diagnostics that entail photoluminescence and photoconductivity measurements in a wide temperature range.