Abstract: Методом субмиллиметровой спектроскопии с высоким временным разрешением при Т = 4.2 К измерена концентрационная зависимость полосы преобразования гетеродинного детектирования гетероструктур AlGaAs/GaAs с двумерным электронным газом. С увеличением концентрации двумерных электронов ns = (1.6–6.6) · 1011см-2 ширина полосы преобразования f3dB уменьшается от 245 до 145 МГц. В исследованной области концентраций наблюдается зависимость f3dB , обусловленная рассеянием электронов на деформационном потенциале акустических фононов и пьезоэлектрическим рассеянием.

Abstract: We describe a novel GaAs/AlGaAs double-quantumwell device for the infrared photon detection, called ChargeSensitive Infrared Phototransistor (CSIP). The principle of CSIP detector is the photo-excitation of an intersubband transition in a QW as an charge integrating gate and the signal ampli<ef><ac><81>cation by another QW as a channel with very high gain, which provides us with extremely high responsivity (104 – 106 A/W). It has been demonstrated that the CSIP designed for the mid-infrared wavelength (14.7 μm) has an excellent sensitivity; the noise equivalent power (NEP) of 7 × 10-19 W/ with the quantum effciency of ~ 2%. Advantages of the CSIP against the other highly sensitive detectors are, huge dynamic range of > 106, low output impedance of 103 – 104 Ohms, and relatively high operation temperature (> 2 K). We discuss possible applications of the CSIP to FIR photon detection covering 35 – 60 μm waveband, which is a gap uncovered with presently available photoconductors.

Abstract: We present a new photon number resolving detector (PNR), the Parallel Nanowire Detector (PND), which uses spatial multiplexing on a subwavelength scale to provide a single electrical output proportional to the photon number. The basic structure of the PND is the parallel connection of several NbN superconducting nanowires (100 nm-wide, few nm-thick), folded in a meander pattern. Electrical and optical equivalents of the device were developed in order to gain insight on its working principle. PNDs were fabricated on 3-4 nm thick NbN films grown on sapphire (substrate temperature TS=900C) or MgO (TS=400C) substrates by reactive magnetron sputtering in an Ar/N2 gas mixture. The device performance was characterized in terms of speed and sensitivity. The photoresponse shows a full width at half maximum (FWHM) as low as 660ps. PNDs showed counting performance at 80 MHz repetition rate. Building the histograms of the photoresponse peak, no multiplication noise buildup is observable and a one photon quantum efficiency can be estimated to be QE=3% (at 700 nm wavelength and 4.2 K temperature). The PND significantly outperforms existing PNR detectors in terms of simplicity, sensitivity, speed, and multiplication noise.

Abstract: We report on low noise terahertz mixers(1.4–1.9THz) developed for the heterodyne spectrometer onboard the Herschel Space Observatory. The mixers employ double slot antenna integrated superconducting hot-electron bolometers (HEBs) made of thin NbN films. The mixer performance was characterized in terms of detection sensitivity across the entire rf band by using a Fourier transform spectrometer (from 0.5to2.5THz, with 30GHz resolution) and also by measuring the mixernoise temperature at a limited number of discrete frequencies. The lowest mixernoise temperature recorded was 750K [double sideband (DSB)] at 1.6THz and 950KDSB at 1.9THz local oscillator (LO) frequencies. Averaged across the intermediate frequency band of 2.4–4.8GHz, the mixernoise temperature was 1100KDSB at 1.6THz and 1450KDSB at 1.9THz LO frequencies. The HEB heterodyne receiver stability has been analyzed and compared to the HEB stability in the direct detection mode. The optimal local oscillator power was determined and found to be in a 200–500nW range.

Abstract: The advantageous properties of terahertz waves, such as their transmission through objects opaque to visible light, are attracting attention for imaging applications. A promising approach for achieving high spatial resolution is the use of near-field imaging. Although this method has been well established in the visible and microwave regions, it is challenging to perform in the terahertz region. In the terahertz techniques investigated to date, detectors have been located remotely from the probe, which degrades sensitivity, and the influence of far-field waves is unavoidable. Here we present a new integrated detection device for terahertz near-field imaging in which all the necessary detection components — an aperture, a probe and a terahertz detector — are integrated on one semiconductor chip, which is cryogenically cooled. This scheme allows highly sensitive, high-resolution detection of the evanescent field alone and promises new capabilities for high-resolution terahertz imaging.