Roles of Elements of a Heterostructure Based on the Topological Phase of Hg1 – xCdxTe in the Effect of PT-Symmetric Terahertz Photoconductivity

JETP Letters - It is demonstrated that the PT-symmetric terahertz photoconductivity observed in heterostructures based on thick Hg1 – xCdxTe films in the topological phase is due to the...     

Photothermal Ionization Spectroscopy of Mercury Vacancies in HgCdTe Epitaxial Films

JETP Letters - The terahertz photoconductivity of narrow-gap Hg1 – xCdxTe alloys that originates from shallow double acceptors formed by mercury vacancies is investigated. The discrete...     

Unveiling Talbot Effect under Fresnel Diffraction at a Fork-Shaped Grating

The near-field effect of diffraction image self-reproduction or self-imaging of a periodic grating illuminated by quasi-monochromatic wave is well-known as the Talbot effect. Introducing a dislocation to a periodic structure provides a fork-shaped modulation of the phase/amplitude, which produces discrete diffraction pattern in a far-field consisting of optical vortices. In this paper, Fresnel diffraction at amplitude fork-shaped grating is theoretically and experimentally studied. The coexistence of spatial ordering and local violation of translational symmetry of the structure manifests itself in a strict diffraction pattern consisting of optical vortices in the far-field, which is shown to be accompanied by formation of a spatially ordered intensity distribution in the near-field, reminiscent the Talbot carpets for periodic structures. These results demonstrate the first evidence of Talbot effect occurred under light diffraction at fork-shaped gratings, being promising for deep understanding of near-field singular optics phenomena.     

Cage‐like Fe,Na‐Germsesquioxanes: Structure,Magnetism, and Catalytic Activity

A series of four unprecedented heterometallic metallagermsesquioxanes were synthesized. Their cage‐like architectures have a unique type of molecular topology consisting of the hexairon oxo {Fe₆O₁₉} core surrounded in a triangular manner by three cyclic germoxanolates [PhGe(O)O]₅. This structural organization induces antiferromagnetic interactions between the Fe^III ions through the oxygen atoms. Evaluated for this first time in catalysis, these compounds showed a high catalytic activity in the oxidation of alkanes and the oxidative formation of benzamides from alcohols.     

Emission spectra of terahertz quantum cascade laser

We calculated energy levels, wave functions, and energies of radiative transitions in terahertz quantum cascade lasers based on GaAs/Al_0.15Ga_0.85As heterostructures. Current-voltage characteristics and current dependences of laser radiation intensity were measured, and the maximum operating temperatures reaching 85 K were determined. Radiation spectra of quantum cascade lasers were measured for different temperatures, and the effect of intensity “pumping” from low-frequency modes to high-frequency modes was found to happen in the case of an increase in the current and time delay of the signal capture, which is explained by heating of the sample during a pulse of the current. Application of the lasers for registration of impurity photoconductivity signals in semiconductor heterostructures was demonstrated.