Ryzhii, V., Otsuji, T., Ryzhii, M., Leiman, V. G., Fedorov, G., Goltzman, G. N., et al. (2016). Two-dimensional plasmons in lateral carbon nanotube network structures and their effect on the terahertz radiation detection. J. Appl. Phys., 120(4), 044501 (1 to 13).
Abstract: We consider the carrier transport and plasmonic phenomena in the lateral carbon nanotube (CNT) networks forming the device channel with asymmetric electrodes. One electrode is the Ohmic contact to the CNT network and the other contact is the Schottky contact. These structures can serve as detectors of the terahertz (THz) radiation. We develop the device model for collective response of the lateral CNT networks which comprise a mixture of randomly oriented semiconductor CNTs (s-CNTs) and quasi-metal CNTs (m-CNTs). The proposed model includes the concept of the collective two-dimensional (2D) plasmons in relatively dense networks of randomly oriented CNTs (CNT “felt”) and predicts the detector responsivity spectral characteristics exhibiting sharp resonant peaks at the signal frequencies corresponding to the 2D plasmonic resonances. The detection mechanism is the rectification of the ac current due the nonlinearity of the Schottky contact current-voltage characteristics under the conditions of a strong enhancement of the potential drop at this contact associated with the plasmon excitation. The detector responsivity depends on the fractions of the s- and m-CNTs. The burning of the near-contact regions of the m-CNTs or destruction of these CNTs leads to a marked increase in the responsivity in agreement with our experimental data. The resonant THz detectors with sufficiently dense lateral CNT networks can compete and surpass other THz detectors using plasmonic effects at room temperatures.
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Iomdina, E. N., Seliverstov, S. V., Teplyakova, K. O., Jani, E. V., Pozdniakova, V. V., Polyakova, O. N., et al. (2021). Terahertz scanning of the rabbit cornea with experimental UVB-induced damage: in vivo assessment of hydration and its verification. J. Biomed. Opt., 26(4).
Abstract: SIGNIFICANCE: Water content plays a vital role in the normally functioning visual system; even a minor disruption in the water balance may be harmful. Today, no direct method exists for corneal hydration assessment, while it could be instrumental in early diagnosis and control of a variety of eye diseases. The use of terahertz (THz) radiation, which is highly sensitive to water content, appears to be very promising. AIM: To find out how THz scanning parameters of corneal tissue measured by an experimental setup, specially developed for in vivo contactless estimations of corneal reflectivity coefficient (RC), are related to pathological changes in the cornea caused by B-band ultraviolet (UVB) exposure. APPROACH: The setup was tested on rabbit eyes in vivo. Prior to the course of UVB irradiation and 1, 5, and 30 days after it, a series of examinations of the corneal state was made. At the same time points, corneal hydration was assessed by measuring RC. RESULTS: The obtained data confirmed the negative impact of UVB irradiation course on the intensity of tear production and on the corneal thickness and optical parameters. A significant (1.8 times) increase in RC on the 5th day after the irradiation course, followed by a slight decrease on the 30th day after it was revealed. The RC increase measured 5 days after the UVB irradiation course generally corresponded to the increase (by a factor of 1.3) of tear production. RC increase occurred with the corneal edema, which was manifested by corneal thickening (by 18.2% in the middle area and 17.6% in corneal periphery) and an increased volume of corneal tissue (by 17.6%). CONCLUSIONS: Our results demonstrate that the proposed approach can be used for in vivo contactless estimation of the reflectivity of rabbit cornea in the THz range and, thereby, of cornea hydration.
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Iomdina, E. N., Goltsman, G. N., Seliverstov, S. V., Sianosyan, A. A., Teplyakova, K. O., & Rusova, A. A. (2016). Study of transmittance and reflectance spectra of the cornea and the sclera in the THz frequency range. J. Biomed. Opt., 21(9), 97002 (1 to 5).
Abstract: An adequate water balance (hydration extent) is one of the basic factors of normal eye function, including its external shells: the cornea and the sclera. Adequate control of corneal and scleral hydration is very important for early diagnosis of a variety of eye diseases, stating indications for and contraindications against keratorefractive surgeries and the choice of contact lens correction solutions. THz systems of creating images in reflected beams are likely to become ideal instruments of noninvasive control of corneal and scleral hydration degrees. This paper reports on the results of a study involving transmittance and reflectance spectra for the cornea and the sclera of rabbit and human eyes, as well as those of the rabbit eye, in the frequency range of 0.13 to 0.32 THz. The dependence of the reflectance coefficient of these tissues on water mass percentage content was determined. The experiments were performed on three corneas, three rabbit scleras, two rabbit eyes, and three human scleras. The preliminary results demonstrate that the proposed technique, based on the use of a continuous THz radiation, may be utilized to create a device for noninvasive control of corneal and scleral hydration, which has clear potential of broad practical application.
Keywords: BWO, IMPATT diode, Schottky diode, medicine, animals, cornea, physiology, humans, rabbits, sclera diagnostic imaging, physiology
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Ozhegov, R. V., Okunev, O. V., Gol’tsman, G. N., Filippenko, L. V., & Koshelets, V. P. (2009). Noise equivalent temperature difference of a superconducting integrated terahertz receiver. J. Commun. Technol. Electron., 54(6), 716–720.
Abstract: The dependence of the noise equivalent temperature difference (NETD) of a superconducting integrated receiver (SIR) on the receiver noise temperature and the inputsignal level has been investigated. An unprecedented NETD of 13±2 mK has been measured at a SIR noise temperature of 200 K, intermediate-frequency bandwidth of 4 GHz, and time constant of 1 s. With a decrease in the input signal, an improvement in the NETD is observed. This effect is explained by a reduction in the influence of the instabilities of the receiver power supply and the amplification circuit that occur when the input signal is decreased.
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Nikogosyan, A. S., Martirosyan, R. M., Hakhoumian, A. A., Makaryan, A. H., Tadevosyan, V. R., Goltsman, G. N., et al. (2019). Effect of absorption on the efficiency of terahertz radiation generation in the metal waveguide partially filled with nonlinear crystal LiNbO3, DAST or ZnTe. J. Contemp. Phys., 54(1), 97–104.
Abstract: The influence of terahertz (THz) radiation absorption on the efficiency of generation of coherent THz radiation in the system ‘nonlinear-optical crystal partially filling the cross section of a rectangular metal waveguide’ has been investigated. The efficiency of the nonlinear frequency conversion of optical laser radiation to the THz range depends on the loss in the system and the fulfillment of the phase-matching (FM) condition in a nonlinear crystal. The method of partially filling of a metal waveguide with a nonlinear optical crystal is used to ensure phase matching. The phase matching is achieved by numerical determination of the thickness of the nonlinear crystal, that is the degree of partial filling of the waveguide. The attenuation of THz radiation caused by losses both in the metal walls of the waveguide and in the crystal was studied, taking into account the dimension of the cross section of the waveguide, the degree of partial filling, and the dielectric constant of the crystal. It is shown that the partial filling of the waveguide with a nonlinear crystal results in an increase in the efficiency of generation of THz radiation by an order of magnitude, owing to the decrease in absorption.
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Milostnaya, I., Korneev, A., Tarkhov, M., Divochiy, A., Minaeva, O., Seleznev, V., et al. (2008). Superconducting single photon nanowire detectors development for IR and THz applications. J. Low Temp. Phys., 151(1-2), 591–596.
Abstract: We present our progress in the development of superconducting single-photon detectors (SSPDs) based on meander-shaped nanowires made from few-nm-thick superconducting films. The SSPDs are operated at a temperature of 2–4.2 K (well below T c ) being biased with a current very close to the nanowire critical current at the operation temperature. To date, the material of choice for SSPDs is niobium nitride (NbN). Developed NbN SSPDs are capable of single photon counting in the range from VIS to mid-IR (up to 6 μm) with a record low dark counts rate and record-high counting rate. The use of a material with a low transition temperature should shift the detectors sensitivity towards longer wavelengths. We present state-of-the art NbN SSPDs as well as the results of our recent approach to expand the developed SSPD technology by the use of superconducting materials with lower T c , such as molybdenum rhenium (MoRe). MoRe SSPDs first were made and tested; a single photon response was obtained.
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de Lara, D. P., Ejrnaes, M., Casaburi, A., Lisitskiy, M., Cristiano, R., Pagano, S., et al. (2008). Feasibility investigation of NbN nanowires as detector in time-of-flight mass spectrometers for macromolecules of interest in biology (proteins). J. Low Temp. Phys., 151(3-4), 771–776.
Abstract: We are investigating the possibility of using NbN nanowires as detectors in time-of-flight mass spectrometers for investigation of macromolecules of interest in biology (proteins). NbN nanowires could overcome the two major drawbacks encountered so far by cryogenic detectors, namely the low working temperature in the mK region and the slow temporal response. In fact, NbN nanowires can work at 5 K and the response time is at least a factor 10–100 better than that of other cryogenic detectors. We present a feasibility study based on a numerical code to calculate the response of a NbN nanowire. The parameter space is investigated at different energies from IR to macromolecules (i.e. from eV to keV) in order to understand if larger value of film thickness and width can be used for the keV energy region. We also present preliminary experimental results of irradiation with X-ray photons of NbN to simulate the effect of macromolecules of the same energy.
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Ovchinnikov, O. V., Perepelitsa, A. S., Smirnov, M. S., Latyshev, A. N., Grevtseva, I. G., Vasiliev, R. B., et al. (2020). Luminescence of colloidal Ag2S/ZnS core/shell quantum dots capped with thioglycolic acid. J. Luminescence, 220, 117008 (1 to 7).
Abstract: The features of IR luminescence of colloidal AgS QDs passivated with thioglycolic acid (AgS/TGA) under the formation of AgS/ZnS/TGA core/shell QDs are considered. A 4.5-fold increase in the quantum yield of recombination IR luminescence within the band with a peak at 960 nm (1.29 eV), full width at half maximum of 250 nm (0.34 eV), and the Stokes shift with respect to the exciton absorption of 0.6 eV was found. The increase in the IR luminescence intensity of AgS/ZnS/TGA QDs is accompanied by an increase in the average luminescence lifetime from 2.9 ns to 14.3 ns, which is explained as “healing” of surface trap states during the formation of the ZnS shell. For the first time, the enhancement of the luminescence intensity photodegradation (hereinafter referred to as fatigue) was found during the formation of the AgS/ZnS/TGA core/shell QDs. The luminescence fatigue is irreversible. We conclude that the initial stage of photolysis of the AgS core QDs under laser irradiation plays a key role. Low-atomic photolytic clusters of silver formed on the AgS core QDs act as luminescence quenching centers and do not reveal structural transformations into AgS, provided that the clusters are not in contact with TGA.
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Goltsman, G., Korneev, A., Divochiy, A., Minaeva, O., Tarkhov, M., Kaurova, N., et al. (2009). Ultrafast superconducting single-photon detector. J. Modern Opt., 56(15), 1670–1680.
Abstract: The state-of-the-art of the NbN nanowire superconducting single-photon detector technology (SSPD) is presented. The SSPDs exhibit excellent performance at 2 K temperature: 30% quantum efficiency from visible to infrared, negligible dark count rate, single-photon sensitivity up to 5.6 µm. The recent achievements in the development of GHz counting rate devices with photon-number resolving capability is presented.
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Dauler, E., Kerman, A., Robinson, B., Yang, J., Voronov, B., Goltsman, G., et al. (2009). Photon-number-resolution with sub-30-ps timing using multi-element superconducting nanowire single photon detectors. J. Modern Opt., 56(2), 364–373.
Abstract: A photon-number-resolving detector based on a four-element superconducting nanowire single photon detector is demonstrated to have sub-30-ps resolution in measuring the arrival time of individual photons. This detector can be used to characterize the photon statistics of non-pulsed light sources and to mitigate dead-time effects in high-speed photon counting applications. Furthermore, a 25% system detection efficiency at 1550 nm was demonstrated, making the detector useful for both low-flux source characterization and high-speed photon-counting and quantum communication applications. The design, fabrication and testing of this detector are described, and a comparison between the measured and theoretical performance is presented.
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Marsili, F., Bitauld, D., Fiore, A., Gaggero, A., Leoni, R., Mattioli, F., et al. (2009). Superconducting parallel nanowire detector with photon number resolving functionality. J. Modern Opt., 56(2-3), 334–344.
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.
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Słysz, W., Wegrzecki, M., Bar, J., Grabiec, P., Górska, M., Zwiller, V., et al. (2007). Fibre-coupled, single photon detector based on NbN superconducting nanostructures for quantum communications. J. Modern Opt., 54(2-3), 315–326.
Abstract: We present a novel, two-channel, single photon receiver based on two fibre-coupled, NbN, superconducting, single photon detectors (SSPDs). The SSPDs are nanostructured superconducting meanders and are known for ultrafast and efficient detection of visible-to-infrared photons. Coupling between the NbN detector and optical fibre was achieved using a micromechanical photoresist ring placed directly over the SSPD, holding the fibre in place. With this arrangement, we obtained coupling efficiencies up to ∼30%. Our experimental results showed that the best receiver had a near-infrared system quantum efficiency of 0.33% at 4.2 K. The quantum efficiency increased exponentially with the photon energy increase, reaching a few percent level for visible-light photons. The photoresponse pulses of our devices were limited by the meander high kinetic inductance and had the rise and fall times of approximately 250 ps and 5 ns, respectively. The receiver's timing jitter was in the 37 to 58 ps range, approximately 2 to 3 times larger than in our older free-space-coupled SSPDs. We stipulate that this timing jitter is in part due to optical fibre properties. Besides quantum communications, the two-detector arrangement should also find applications in quantum correlation experiments.
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Verevkin, A., Pearlman, A., Slysz, W., Zhang, J., Currie, M., Korneev, A., et al. (2004). Ultrafast superconducting single-photon detectors for near-infrared-wavelength quantum communications. J. Modern Opt., 51(9-10), 1447–1458.
Abstract: The paper reports progress on the design and development of niobium-nitride, superconducting single-photon detectors (SSPDs) for ultrafast counting of near-infrared photons for secure quantum communications. The SSPDs operate in the quantum detection mode, based on photon-induced hotspot formation and subsequent appearance of a transient resistive barrier across an ultrathin and submicron-width superconducting stripe. The devices are fabricated from 3.5 nm thick NbN films and kept at cryogenic (liquid helium) temperatures inside a cryostat. The detector experimental quantum efficiency in the photon-counting mode reaches above 20% in the visible radiation range and up to 10% at the 1.3–1.55 μn infrared range. The dark counts are below 0.01 per second. The measured real-time counting rate is above 2 GHz and is limited by readout electronics (the intrinsic response time is below 30 ps). The SSPD jitter is below 18 ps, and the best-measured value of the noise-equivalent power (NEP) is 2 × 10−18 W/Hz1/2. at 1.3 μm. In terms of photon-counting efficiency and speed, these NbN SSPDs significantly outperform semiconductor avalanche photodiodes and photomultipliers.
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Vakhtomin, Y. B., Finkel, M. I., Antipov, S. V., Smirnov, K. V., Kaurova, N. S., Drakinskii, V. N., et al. (2003). The gain bandwidth of mixers based on the electron heating effect in an ultrathin NbN film on a Si substrate with a buffer MgO layer. J. of communications technol. & electronics, 48(6), 671–675.
Abstract: Measurements of the intermediate frequency band 900 GHz of mixers based on the electron heating effect (EHE) in 2-nm- and 3.5-nm-thick superconducting NbN films sputtered on MgO and Si substrates with buffer MgO layers are presented. A 2-nm-thick superconducting NbN film with a critical temperature of 9.2 K has been obtained for the first time using a buffer MgO layer.
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Boyarskii, D. A., Gershenzon, V. E., Gershenzon, E. M., Gol'tsman, G. N., Ptitsina, N. G., Tikhonov, V. V., et al. (1996). On the possibility of determining the microstructural parameters of an oil-bearing layer from radiophysical measurement data. J. of Communications Technology and Electronics, 41(5), 408–414.
Abstract: A method for the reconstruction of microstructural properties of an oil-bearing rock from the spectral dependence of the transmission factor of submillimeter waves is proposed.
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