Experimental demonstration of ghost imaging with speckled light in long-wavelength infrared range

Infrared imaging with a single-pixel camera can achieve radiometric accuracy not currently available with multi-pixel thermal cameras. One of the actively investigated single-pixel camera technology is ghost imaging. We propose an optical design to experimentally demonstrate classical ghost imaging in the long-wave infrared frequency range with speckled light without using a spatial light modulator. We obtained an example low-quality ghost image and then used the cross-correlation function to identify and explain the main difficulties in ghost imaging with a thermal camera.

Graphene-based tunable broadband polarizer for infrared frequency

This paper proposes the tunable graphene-assisted polarizer structure which is working on the infrared frequency range. The tunable polarizer has been designed by a three-layered structure of silica, graphene, and gold. The polarizer behavior of the structure is analyzed for the frequency range of 3 to 12 THz. The tunability of the structure is analyzed for the different values of fermi energy which is tunable parameter of single-layer graphene sheet. Polarizer response is derived in terms of different performance parameters such as reflectance, phase variation, phase difference, polarization conversion rate, and effective refractive indices. Graphene-based polarizer structure is investigated for the co-polarization and cross-polarization input incident conditions to check linear to circular polarization conversion. It also shows an effective refractive index response to check the metasurface behavior of the polarizer for 3 to 12 THz range. We have observed that the polarization amplitude becomes stronger for the higher Fermi energy value of the graphene sheet. The reflection amplitude is achieved up to 90%. Results of the proposed polarizer structure can be used to design the various electro-optical structure which operates in the lower THz range.

Sub-diffractional cavity modes of terahertz hyperbolic phonon polaritons in tin oxide

Hyperbolic phonon polaritons have recently attracted considerable attention in nanophotonics mostly due to their intrinsic strong electromagnetic field confinement, ultraslow polariton group velocities, and long lifetimes. Here we introduce tin oxide (SnO2) nanobelts as a photonic platform for the transport of surface and volume phonon polaritons in the mid- to far-infrared frequency range. This report brings a comprehensive description of the polaritonic properties of SnO2 as a nanometer-sized dielectric and also as an engineered material in the form of a waveguide. By combining accelerator-based IR-THz sources (synchrotron and free-electron laser) with s-SNOM, we employed nanoscale far-infrared hyper-spectral-imaging to uncover a Fabry–Perot cavity mechanism in SnO2 nanobelts via direct detection of phonon-polariton standing waves. Our experimental findings are accurately supported by notable convergence between theory and numerical simulations. Thus, the SnO2 is confirmed as a natural hyperbolic material with unique photonic properties essential for future applications involving subdiffractional light traffic and detection in the far-infrared range.

МОДЕЛИРОВАНИЕ И РАСЧЕТ СПЕКТРА ФОТОЛЮМИНЕСЦЕНЦИИ ГЕТЕРОСТРУКТУРЫ С КВАНТОВОЙ ЯМОЙ НА ПРИМЕРЕ ALGaAS/GaAS

This research aims to improve the available means for characterizing the emission properties of quantum well heterostructures by modeling and calculating the absorption and photoluminescence spectra using the GaAs/AlGaAs heterostructure as an example. Research is conducted based on multilayer heterostructures and heterostructures with quantum wells to develop detectors and emitting elements in the infrared frequency range, pulsed solid-state generators in the millimeter and submillimeter-wave ranges. The study of radiating properties of heterostructures with a quantum well on A3B5 compounds has become widespread [1-3]. It is possible to control the heterostructure's emission frequency by selecting the optimal composition of the wideband semiconductor layer, the level and type of its doping, the doping region, and the quantum well layer width, which is of applied importance for the development of optoelectronic devices. Technologies for manufacturing such heterostructures are labor-intensive, time-consuming, and expensive processes, which contribute to developing methods for modeling and calculating the characteristic frequencies of radiation and absorption of radiation. Based on such calculations, radiating elements of the submicronic wavelength range can be developed based on heterostructures with a quantum well on the A3B5 type compounds. [4]

МОДЕЛИРОВАНИЕ И РАСЧЕТ СПЕКТРА ФОТОЛЮМИНЕСЦЕНЦИИ ГЕТЕРОСТРУКТУРЫ С КВАНТОВОЙ ЯМОЙ НА ПРИМЕРЕ ALGaAS/GaAS

This research aims to improve the available means for characterizing the emission properties of quantum well heterostructures by modeling and calculating the absorption and photoluminescence spectra using the GaAs/AlGaAs heterostructure as an example. Research is conducted based on multilayer heterostructures and heterostructures with quantum wells to develop detectors and emitting elements in the infrared frequency range, pulsed solid-state generators in the millimeter and submillimeter-wave ranges. The study of radiating properties of heterostructures with a quantum well on A3B5 compounds has become widespread [1-3]. It is possible to control the heterostructure's emission frequency by selecting the optimal composition of the wideband semiconductor layer, the level and type of its doping, the doping region, and the quantum well layer width, which is of applied importance for the development of optoelectronic devices. Technologies for manufacturing such heterostructures are labor-intensive, time-consuming, and expensive processes, which contribute to developing methods for modeling and calculating the characteristic frequencies of radiation and absorption of radiation. Based on such calculations, radiating elements of the submicronic wavelength range can be developed based on heterostructures with a quantum well on the A3B5 type compounds. [4]

A test of the ability of current bulk optical models to represent the radiative properties of cirrus cloud across the mid- and far-infrared

Measurements of mid- to far-infrared nadir radiances obtained from the UK Facility for Airborne Atmospheric Measurements (FAAM) BAe 146 aircraft during the Cirrus Coupled Cloud-Radiation Experiment (CIRCCREX) are used to assess the performance of various ice cloud bulk optical property models. Through use of a minimization approach, we find that the simulations can reproduce the observed spectra in the mid-infrared to within measurement uncertainty, but they are unable to simultaneously match the observations over the far-infrared frequency range. When both mid- and far-infrared observations are used to minimize residuals, first-order estimates of the spectral flux differences between the best-performing simulations and observations indicate a compensation effect between the mid- and far-infrared such that the absolute broadband difference is < 0.7 W m−2. However, simply matching the spectra using the mid-infrared (far-infrared) observations in isolation leads to substantially larger discrepancies, with absolute differences reaching ∼ 1.8 (3.1) W m−2. These results show that simulations using these microphysical models may give a broadly correct integrated longwave radiative impact but that this masks spectral errors, with implicit consequences for the vertical distribution of atmospheric heating. They also imply that retrievals using these models applied to mid-infrared radiances in isolation will select cirrus optical properties that are inconsistent with far-infrared radiances. As such, the results highlight the potential benefit of more extensive far-infrared observations for the assessment and, where necessary, the improvement of current ice bulk optical models.

Temperature-dependent optical and vibrational properties of PtSe2 thin films

PtSe2 has received substantial research attention because of its intriguing physical properties and potential practical applications. In this paper, we investigated the optical properties of bilayer and multilayer PtSe2 thin films through spectroscopic ellipsometry over a spectral range of 0.73–6.42 eV and at temperatures between 4.5 and 500 K. At room temperature, the spectra of refractive index exhibited several anomalous dispersion features below 1000 nm and approached a constant value in the near-infrared frequency range. The thermo-optic coefficients of bilayer and multilayer PtSe2 thin films were (4.31 ± 0.04) × 10−4/K and (–9.20 ± 0.03) × 10−4/K at a wavelength of 1200 nm. Analysis of the optical absorption spectrum at room temperature confirmed that bilayer PtSe2 thin films had an indirect band gap of approximately 0.75 ± 0.01 eV, whereas multilayer PtSe2 thin films exhibited semimetal behavior. The band gap of bilayer PtSe2 thin films increased to 0.83 ± 0.01 eV at 4.5 K because of the suppression of electron–phonon interactions. Furthermore, the frequency shifts of Raman-active Eg and A1g phonon modes of both thin films in the temperature range between 10 and 500 K accorded with the predictions of the anharmonic model. These results provide basic information for the technological development of PtSe2-based optoelectronic and photonic devices at various temperatures.