arXiv subjects

Aleksandr S. Baburin

Publications and source records attributed to Aleksandr S. Baburin.

9 recordsLinked to original sources

arXiv2026

Superconducting single-photon detectors for integrated quantum photonics

Single-photon detection possibility is a fundamental requirement for quantum technologies, including communication, computing and sensing. To achieve scalability and practical deployment, increasing attention is being directed toward integration of detectors with photonic integrated circuits, which offer compactness and compatibility with mass production. Superconducting nanowire single-photon detectors have emerged as the leading solution, combining near-unity efficiency, high temporal performance and the ability to be embedded across a wide range of photonic material platforms. In this review we trace the development of integrated superconducting nanowire single-photon detectors from early demonstrations to recent advances, outlining the progress in device architectures, material engineering and integration strategies. We also discuss performance benchmarks, emerging alternative designs, the future opportunities and challenges for this rapidly evolving field.

physics.optics↗

arXiv2024

Tutorial on Silicon Photonics Integrated Platform Fiber Edge Coupling

Photonic integrated circuits (PICs) play a crucial role in almost every aspect of modern life, such as data storage, telecommunications, medical diagnostics, green energy, autonomous driving, agriculture, and high-performance computing. To fully harness their benefits, an efficient coupling mechanism is required to successfully launch light into waveguides from fibers. This study introduces low-loss coupling strategies and their implementation for a silicon nitride integrated platform. Here we present an overview of coupling technologies, optimized designs, and a tutorial on manufacturing techniques for inverted tapers, which enable effective coupling for both transverse-magnetic and transverse-electric modes. The optimized coupling losses for the UHNA-7 fiber and the inverted taper Si3N4 coupler reached -0.15 dB at 1550 nm per connection for single-mode waveguides with 220x1200 nm cross section. The measured coupling losses in the inverted taper coupler with a standard single-mode fiber were -1.50 dB at 1550 nm per connection for the same platform.

physics.optics↗

arXiv2024

Silicon nitride integrated photonics from visible to mid-infrared spectra

Recently, silicon nitride (Si3N4) photonic integrated circuits (PICs) are of a great interest due to their extremely low waveguides losses. The number of Si3N4 integrated photonics platform applications is constantly growing including the Internet of Things (IoT), artificial intelligence (AI), light detection and ranging (LiDAR) devices, hybrid neuromorphic and quantum computing. Their heterogeneous integration with a III-V platform leads to a new advanced large scale PICs with thousands of elements. Here, we review key trends in Si3N4 integrated circuits technology and fill an information gap in the field of state-of-the-art photonic devices operating from visible to mid-infrared spectra. A comprehensive overview of Si3N4 integrared circtuis microfabrication process details (deposition, lithography, etching, etc.) is introduced. Finally, we point out the limits and challenges of silicon nitride photonics performance in an ultrawide range providing routes and prospects for their future scaling and optimization.

physics.optics↗

arXiv2023

Sputtered NbN Films for Ultrahigh Performance Superconducting Nanowire Single-Photon Detectors

Nowadays ultrahigh performance superconducting nanowire single-photon detectors are the key elements in a variety of devices from biological research to quantum communications and computing. Accurate tuning of superconducting material properties is a powerful resource for fabricating single-photon detectors with a desired properties. Here, we report on the major theoretical relations between ultrathin niobium nitride (NbN) films properties and superconducting nanowire single-photon detectors characteristics, as well as ultrathin NbN films properties dependence on reactive magnetron sputtering recipes. Based on this study we formulate the exact requirements to ultrathin NbN films for ultrahigh performance superconducting nanowire single-photon detectors. Then, we experimentally study ultrathin NbN films properties (morphology, crystalline structure, critical temperature, sheet resistance) on silicon, sapphire, silicon dioxide and silicon nitride substrates sputtered with various recipes. We demonstrate ultrathin NbN films (obtained with more than 100 films deposition) with a wide range of critical temperature from 2.5 to 12.1 K and sheet resistance from 285 to 2000 ~$Ω$/sq, as well as investigate a sheet resistance evolution over for more than 40\% within two years. Finally, we found out that one should use ultrathin NbN films with specific critical temperature near 9 K and sheet resistance of 400 ~$Ω$/sq for ultrahigh performance SNSPD.

cond-mat.supr-con↗

arXiv2022

Low-loss silicon nitride photonic ICs for single-photon applications

Low-loss photonic integrated circuits (PICs) are the key elements in future quantum technologies, nonlinear photonics and neural networks. The low-loss photonic circuits technology targeting C-band application is well established across multi-project wafer (MPW) fabs, whereas near-infrared (NIR) PICs suitable for the state-of-the-art single-photon sources are still underdeveloped. Here, we report the labs-scale process optimization and optical characterization of low-loss tunable photonic integrated circuits for single-photon applications. We demonstrate the lowest propagation losses to the date (as low as 0.55 dB/cm at 925 nm wavelength) in single-mode silicon nitride submicron waveguides (220x550 nm). This performance is achieved due to advanced e-beam lithography and inductively coupled plasma reactive ion etching steps which yields waveguides vertical sidewalls with down to 0.85 nm sidewall roughness. These results provide a chip-scale low-loss PIC platform that could be even further improved with high quality SiO2 cladding, chemical-mechanical polishing and multistep annealing for extra-strict single-photon applications.

physics.optics↗

arXiv2022

Beyond single-crystalline metals: ultralow-loss silver films on lattice-mismatched substrates

High-quality factor plasmonic devices are crucial components in the fields of nanophotonics, quantum computing and sensing. The majority of these devices are required to be fabricated on non-lattice matched or transparent amorphous substrates. Plasmonic devices quality factor is mainly defined by ohmic losses, scattering losses at grain boundaries, and in-plane plasmonic scattering losses of a metal - substrate system. Here, we demonstrate the deposition technique to e-beam evaporate ultralow-loss silver thin films on transparent lattice-mismatched substrates. The process is based on evolutionary selection growth. The key feature of our approach is a well-defined control of deposition on a cooled substrate, self-crystallization and subsequent annealing for precise stress relaxation that promote further grains growth. We are able to deposit 100-nm thick ultraflat polycrystalline silver films with micrometer-scale grains and ultralow optical losses. Finally, we show ultra-high-quality factor plasmonic silver nanostructures on transparent lattice-mismatched substrate comparable to epitaxial silver. This can be of the great interest for high performance or single-molecule optical sensorics applications.

physics.optics↗

arXiv2022

Greatly Enhanced Emission from Spin Defects in Hexagonal Boron Nitride Enabled by a Low-Loss Plasmonic Nano-Cavity

Two-dimensional hexagonal boron nitride (hBN) has been known to host a variety of quantum emitters with properties suitable for a broad range of quantum photonic applications. Among them, the negatively charged boron vacancy (VB-) defect with optically addressable spin states has emerged recently due to its potential use in quantum sensing. Compared to spin defects in bulk crystals, VB- preserves its spin coherence properties when placed at nanometer-scale distances from the hBN surface, enabling nanometer-scale quantum sensing. On the other hand, the low quantum efficiency of VB- has hindered its use in practical applications. Several studies have reported improving the overall quantum efficiency of VB- defects using plasmonic effects; however, the overall enhancements of up to 17 times reported to date are relatively modest. In this study, we explore and demonstrate much higher emission enhancements of VB- with ultralow-loss nano-patch antenna (NPA) structures. An overall intensity enhancement of up to 250 times is observed for NPA-coupled VB- defects. Since the laser spot exceeds the area of the NPA, where the enhancement occurs, the actual enhancement provided by the NPA is calculated to be ~1685 times, representing a significant increase over the previously reported results. Importantly, the optically detected magnetic resonance (ODMR) contrast is preserved at such exceptionally strong enhancement. Our results not only establish NPA-coupled VB- defects as high-resolution magnetic field sensors operating at weak laser powers, but also provide a promising approach to obtaining single VB- defects.

physics.optics↗

arXiv2018

Quantum Engineering of Single-Crystalline Silver Thin Films

There is a demand for the manufacture of ultra low-loss metallic films with high-quality single crystals and surface for quantum optics and quantum information processing. Many researches are devoted to alternative materials, but silver is by far the most preferred low-loss material at optical and near-IR frequencies. Usually, epitaxial growth is used to deposit single-crystalline silver films, but they still suffer from losses and well-known deweting effect. Here we report the two-step approach for e-beam evaporation of atomically smooth single-crystalline metallic films. The proposed method is self-controlled by quantum size effects and is based on the step switch of film growth kinetics between two deposition steps, which allow to overcome the film-surface dewetting. Here we have used it to deposit 35-100 nm thick single-crystalline silver films with sub-100 pm surface roughness and extremely low losses. We anticipate that the proposed approach could be readily adopted for the synthesis of other low-loss single-crystalline metallic thin films.

cond-mat.mtrl-sci↗

arXiv2018

Toward theoretically limited SPP propagation length above two hundred microns on ultra-smooth silver surface

We demonstrate the optical medium for surface plasmon - polariton waves (SPP) propagation with ultra low losses corresponding to the theoretically limited values. The unique element of the optical medium is an atomically-flat single-crystalline silver thin film which provides extremely low losses. The SPP excited on the surface of such thin films (at 780 nm) is characterized by a SPP propagation length equals to 200 um, which is twice longer than previously reported experimental results and corresponds to theoretically limited values for silver films.

physics.optics↗