The PT -symmetric photoconductivity has been detected for the first time in microwave-irradiated heterostructures based on thick Hg 1 − x Cd x Te films with the CdTe content x corresponding to the topological phase although the magnetic field symmetry ( T symmetry) and the symmetry in the positions of potential contact pairs ( P symmetry) are not conserved separately. The microwave photoconductivity in similar heterostructures based on the trivial Hg 1 − x Cd x Te phase is both P - and T -symmetric.

Positive photoconductivity stimulated by microwave radiation has been observed in Hg 1 – x Cd x Te thick films being in the topological phase at x < 0.16. The effect amplitude is significant at the liquid helium temperatures, and rapidly decreases with the temperature rising. A mechanism for the positive photoconductivity appearance in the topological phase films is suggested.

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 photoexcitation of charge carriers in the film bulk. At the same time, the place of localization of the effect is the topological film–trivial buffer layer heterointerface. The model describing such a spatial separation of the source of nonequilibrium charge carriers and the effect localization is discussed.

In this paper, we report on observation of a new effect—asymmetric in a magnetic field photoconductivity stimulated by radiofrequency pulses in heterostructures based on thick Hg1−xCdxTe films with composition x < 0.16 corresponding to the topological phase. At certain values of the excitation frequency, the photoconductivity may even change sign when the magnetic field is reversed. Possible mechanisms responsible for the effect appearance are discussed.

Modern space-based telescopes operating in the terahertz (THz) spectral range require highly reflecting and cryogenically cooled optics ensuring extremely low noise. The idea of using high-temperature superconductor YBa2Cu3O7-delta as a telescope's mirror coating for providing low dissipation and high reflectivity of the surface for the subTHz frequency band has been explored. We are presenting here some results of measurements of the reflection losses in YBa2Cu3O7-delta at cryogenic and room temperatures (4.2-300 K) in the frequency band 0.166-0.23 THz. High-accuracy measurements of the absolute value of reflectivity have been performed with the help of the resonance technique. The measured reflection losses in the given frequency band were below 1%. For the same frequency range, these values are well above the reflection losses in normal metals such as copper or aluminum, which are normally used to covermirrors of telescopes. We, therefore, conclude that the use of high-T-c superconductors YBa2Cu3O7-delta as a highly reflecting coating for the THz telescope's mirror is not advisable.

In this article, photoconductivity spectra were studied by Fourier-transform spectroscopy in a solid solution of Pb1–xSnxTe(In)) at low temperatures. It is shown that quenching of persistent photoconductivity in Pb1–xSnxTe(In) by radio pulses of very high frequency (100–200 MHz) can be used to obtain spectra using a Fourier-transform spectrometer. In the spectra, the interband absorption band was observed, and the temperature dependence of its red cut-off boundary was determined.

We present results of an experimental study concentrated on performance optimization of highly sensitive Pb 1-x Sn x Te(In) terahertz photodetectors perspective for applications in the terahertz astronomy. The optimization was reached trough variation of the regime of persistent photoconductivity quenching by radio-frequency pulses. It is demonstrated that the quenching effectiveness rises rapidly with decreasing the radio-frequency in a quenching pulse. In certain regimes, the quenching boosts the photoresponse after the end of the radio-frequency pulse. Possible mechanisms of the radio-frequency quenching of the terahertz persistent photoconductivity in Pb 1-x Sn x Te(In) are discussed.

We report on first results obtained with the use of a new setup for direct passive measurements of the low temperature terahertz emissivity of different materials - metals, superconductors, and others. The setup allows estimating the level of noise originating from the thermal radiation of mirrors in terahertz space missions. This setup also makes it possible to develop the passive terahertz emissivity spectroscopy of different materials.

We report on the physical principles of operation of a passive terahertz imager based on Pb1-xSnxTe(In). First results on construction of such an imager are presented.

Doping of the lead telluride and related alloys with the group III impurities results in appearance of the unique physical features of a material, such as persistent photoresponse, enhanced responsive quantum efficiency (up to 100 photoelectrons/incident photon), radiation hardness and many others. We present the physical principles of operation of the photodetecting devices based on the group III-doped IV-VI including the possibilities of a fast quenching of the persistent photoresponse, construction of the focal-plane array, new readout technique, and others. The advantages of infrared photodetecting systems based on the group III-doped IV-VI in comparison with the modern photodetectors are summarized. The spectra of the persistent photoresponse have not been measured so far because of the difficulties with screening the background radiation. We report on the observation of strong persistent photoconductivity in Pb0.75Sn0.25Te(In) under the action of monochromatic submillimeter radiation at wavelengths of 176 and 241 microns. The sample temperature was 4.2 K, the background radiation was completely screened out. The sample was initially in the semiinsulating state providing dark resistance of more than 100 GOhm. The responsivity of the photodetector is by several orders of magnitude higher than in the state of the art Ge(Ga). The red cut-off wavelength exceeds the upper limit of 220 microns observed so far for the quantum photodetectors in the uniaxially stressed Ge(Ga). It is possible that the photoconductivity spectrum of Pb1-xSnxTe(In) covers all the submillimeter wavelength range.

Doping of the lead telluride and related alloys with the group III impurities results in appearance of the unique physical features of a material, such as persistent photoresponse, enhanced responsive quantum efficiency (up to 100 photoelectrons/incident photon), radiation hardness and many others. We present the physical principles of operation of the photodetecting devices based on the group III-doped IV-VI including the possibilities of a fast quenching of the persistent photoresponse, construction of the focal-plane array, new readout technique, and others. The advantages of infrared photodetecting systems based on the group III-doped IV-VI in comparison with the modern photodetectors are summarized. The spectra of the persistent photoresponse have not been measured so far because of the difficulties with screening the background radiation. We report on the observation of strong persistent photoconductivity in Pb0.75Sn0.25Te(In) under the action of monochromatic submillimeter radiation at wavelengths of 176 and 241 microns. The sample temperature was 4.2 K, the background radiation was completely screened out. The sample was initially in the semiinsulating state providing dark resistance of more than 100 GOhm. The responsivity of the photodetector is by several orders of magnitude higher than in the state of the art Ge(Ga). The red cut-off wavelength exceeds the upper limit of 220 microns observed so far for the quantum photodetectors in the uniaxially stressed Ge(Ga). It is possible that the photoconductivity spectrum of Pb1-xSnxTe(In)covers all the submillimeter wavelength range.

Doping of the lead telluride and related alloys with the group III impurities results in appearance of the unique physical features of a material, such as persistent photoresponse, enhanced responsive quantum efficiency (up to 100 photoelectrons/incident photon), radiation hardness and many others. We present the physical principles of operation of the photodetecting devices based on the group III-doped IV-VI including the possibilities of a fast quenching of the persistent photoresponse, construction of the focal-plane array, new readout technique, and others. The advantages of infrared photodetecting systems based on the group III-doped IV-VI in comparison with the modern photodetectors are summarized. The spectra of the persistent photoresponse have not been measured so far because of the difficulties with screening the background radiation. We report on the observation of strong persistent photoconductivity in Pb 0.75 Sn 0.25 Te(In) under the action of monochromatic submillimeter radiation at wavelengths of 176 and 241 microns. The sample temperature was 4.2 K, the background radiation was completely screened out. The sample was initially in the semiinsulating state providing dark resistance of more than 100 GOhm. The responsivity of the photodetector is by several orders of magnitude higher than in the state of the art Ge(Ga). The red cut-off wavelength exceeds the upper limit of 220 microns observed so far for the quantum photodetectors in the uniaxially stressed Ge(Ga). It is possible that the photoconductivity spectrum of Pb 1-x Sn x Te(In)covers all the submillimeter wavelength range.

Doping of the lead telluride and related alloys with the group III impurities results in appearance of the unique physical features of a material, such as persistent photoresponse, enhanced responsive quantum efficiency (up to 100 photoelectrons/incident photon), high radiation hardness and many others. We present the physical principles of operation of the photodetecting devices based on the group III-doped IV-VI including the possibilities of a fast quenching of the persistent photoresponse, construction of the focal-plane array, and others. We report on the performance of lead telluride-based single direct detectors. The optical NEP as low as 6*10 -20 W/Hz 1/2 at T=1.57 K has been demonstrated at the wavelength of 350 m. The advantages of terahertz photodetecting systems based on the group III-doped IV-VI are summarized.