Гольцман Григорий Наумович

Dark Counts Studied with Spatial Resolution, IEEE Transactions on Applied Superconductivity

2023 · ARTICLE · en

We investigate dark counts in SNSPD with spatial resolution, using nanostrip-patterned devices with 50 Ohm matched coplanar waveguide - tapers. We found that the dark counts originate from one or several points along the strip, which we call 'weak points'. We found that the dark counts originating from different points can have different dependence of the rate on the temperature, such as the point which makes the main contribution to the dark counts rate at low temperature, makes just a minor contribution or even disappears at higher temperature. We explain this in terms of different realizations of random local environments of different ‘weak points’. Then we tilt the distribution of supercurrent density with a weak perpendicular magnetic field and find that the evolution of count rates generated at different ‘weak points’ is consistent with the suggestion that these ‘weak points’ are located at the edges of the strip. All our findings agree with the picture of fluctuating vortex entry through the minima of the order parameter at the edge of the strip as the origin of dark counts in SNSPD.

Dark Counts in SNSPD Studied With Spatial Resolution

2023 в печати · ARTICLE · en

Thermal phase shift in THz silicon effective-medium waveguide

2023 в печати · ARTICLE · en

High-resistivity niobium nitride films for saturated-efficiency SMSPDs at telecom wavelengths and beyond

2023 в печати · ARTICLE · en

DIGITAL PHASE SHIFTER ARRAYS FOR BEAMFORMING IN SUB-THZ COMMUNICATIONS

2023 · CHAPTER · en

Single-particle states spectroscopy in individual carbon nanotubes with an aid of tunneling contacts

2022 · ARTICLE · en

Recent studies have demonstrated that the band structure of a carbon nanotube (CNT) depends not only on its geometry but also on various factors such as atmosphere chemical composition and dielectric environment. Systematic studies of these effects require an efficient tool for an in situ investigation of a CNT band structure. In this work, we fabricate tunneling contacts to individual semiconducting carbon nanotubes through a thin layer of alumina and perform tunneling spectroscopy measurements. We use field-effect transistor configuration with four probe contacts (two tunnel and two ohmic) and bottom gates. Bandgap values extracted from tunneling measurements match the values estimated from the diameter value within the zone-folding approximation. We also observe the splitting of Van-Hove singularities of the density of states under an axial magnetic field.

Measuring Hot-Spot Interaction Length in Single-Strip SNSPD

2022 · ARTICLE · en

Работа сверхпроводниковых однофотонных детекторов (SNSPD) основана на локальном подавлении сверхпроводящего параметра порядка при поглощении фотонов, что вызывает изменение сопротивления, которое может быть обнаружено как импульс постоянного напряжения. Экспериментальное определение размера и профиля области подавления сверхпроводящего параметра порядка (так называемого «горячего пятна») является сложной задачей. В этой работе сообщается о результатах квантовой томографии сверхпроводникового однофотонного детектора микронной длины. Высокая внутренняя эффективность обнаружения SNSPD позволила извлечь одно- и двухфотонную эффективность из зависимости скорости счета от мощности излучения и определить длину взаимодействия горячих пятен. Исследовалась серия образцов, изготовленных из пленок NbN с разным поверхностным сопротивлением и пленки MoSi с различной шириной полоски. Экспериментальные результаты подтвердили, что независимо от материала или сопротивления пленки длина взаимодействия горячих пятен совпадает с шириной полосы, что является многообещающей характеристикой для создания двухфотонного счетчика с высокой точностью.

2022 Photonics & Electromagnetics Research Symposium (PIERS)

2022 · BOOK · en

Here, we report on our recent efforts to develop of a photodetector based on single-layer graphene two-terminal device on the sapphire substrate. Our detector operates at , which corresponds to the telecom window. We have demonstrated that our detector operates under zero bias conditions at room temperature, and the signal-to-noise ratio reaches 45dB. The measured frequency bandwidth reaches 20GHz and is limited by the available experimental equipment.

Towards the Development of Ultrafast Photodetectors Based on Graphene for the Next-generation Telecommunication Systems

2022 · CHAPTER · en

Here, we report on our recent efforts to develop of a photodetector based on single-layer graphene two-terminal device on the sapphire substrate. Our detector operates at 1.55μm, which corresponds to the telecom window. We have demonstrated that our detector operates under zero bias conditions at room temperature, and the signal-to-noise ratio reaches 45dB. The measured frequency bandwidth reaches 20GHz and is limited by the available experimental equipment.

Thermal Relaxation in NbN Films on Crystalline Substrates

2022 · ARTICLE · en

Here we focus on thermal transport in NbN films, deposited on crystalline substrates. Using the noise thermometry, we found that thermal relaxation in thin NbN films at temperatures above the critical superconducting temperature is mainly restricted by the thermal boundary resistance, and it can be modified by a structural disorder on a substrate surface. In addition, for thick NbN films deposited on a sapphire substrate, we observe that thermal relaxation occurs in the diffusive phonon regime when the phonon mean free path is shorter than the film thickness. The findings can be exploited for low-temperature devices based on NbN films. © 2002-2011 IEEE.