We propose a terahertz (THz) plasmonic photoconductive antenna (PCA) with a record height of its metal electrodes of h = 100 nm and a high aspect ratio of h / p = 0.5 ( p is the period of the plasmonic grating) that can be used as a source is THz pulsed spectroscopic and imaging systems. We experimentally demonstrate that the power of the THz radiation generated by the proposed plasmonic PCA is two orders of magnitude higher than that of an equivalent ordinary PCA without a plasmonic grating. Current–voltage measurements of the thus developed plasmonic PCA under femtosecond laser excitation show that the photocurrent of the PCA increases 15-fold, up to i _p ≈ 1.2 mA. To reduce the leakage currents of the PCA, we propose a fabrication technology that is based on the etching of windows in a thin Si_3N_4 passivation dielectric layer deposited on the photoconductor surface, which makes it possible to reduce the dark current to i _d ≈ 5 μA.

Using methods of infrared, terahertz, and submillimeter spectroscopy, experimental transmission and reflection spectra of α-lactose monohydrate have been obtained at room temperature in the frequency range from 5 to 5000 cm^–1. The experimental spectra of dense pressed tablets and powdered samples have been analyzed in terms of the model of a classical oscillator. Certain parameters of absorption bands of the resonant and quasi-relaxation types are markers by which components can be selected in heterogeneous pharmacological and organic preparations using the methods of coherent submillimeter and pulsed terahertz spectroscopy.

Методами широкополосной диэлектрической спектроскопии изучено влияние замещения ионов Fe 3+ на ионы Sc 3+ в системе твердых растворов семейства перовскита Pb(Fe 1−x Scx) 2/3 W 1/3 O 3 на функцию диэлектрического отклика в диапазоне частот от 120 Hz до 100 THz (4 • 10 −9 −3 • 10 3 сm −1). Полученные экспериментальные данные проанализированы в рамках многопараметрических моделей дисперсии. Обсуждается эволюция дисперсионных параметров полос поглощения от степени катионного замещения в B-позиции базиса перовскита ABO 3. Работа выполнена при финансовой поддержке Российского фонда фундаментальных исследований, грант № 16-02-00223, синтез керамик и проведение измерений в низкочастотном диапазоне финансировались по проекту № 3.1099.2017/ПЧ гос. задания Министерства образования и науки РФ.

We report on the experimental study of the photoconductive antennas (PCAs) - detectors based on superlattice heterostructures (SLS) InGaAs/InAs/InAlAs with different types of elastic stresses in their functional layers. By using our laboratory time-domain THz spectrometer we measured and compared the detected THz signals, noise characteristics, and signal-to-noise ratios of the developed bow-tie PCA-detectors at different average probe power. We showed that the SLS-based PCA-detector with elastic stresses of both compression and tension in the layers demonstrates increased THz detection bandwidth compared to that for the SLS-based PCA-detector with only compression stresses in the SLS layers in the whole range of the optical probe power. We thus demonstrate that modification of the SLS via introduction of the elastic strain in the crystalline lattice of its layers could become an efficient approach to enhance the PCA-detectors performance leading to implementation of these PCAs to the spectroscopic THz setups.

2 Институт электронной физики НАН Украины 88017, Ужгород, ул. Университетская, 21 ИССЛЕДОВАНИЕ ДОЛГОЖИВУЩИХ ПРОДУКТОВ ДЕЛЕНИЯ 181 Та Представлены результаты теоретических и экспериментальных исследований долгоживущих радиоактивных продуктов деления атома 181 Та. Ключевые слова: деление ядер, гамма-спектроскопия, 181 Та.