We investigate the temporal and spatial scales of resistance fluctuations (R-fluctuations) at the superconducting resistive transition in thin epitaxial TiN films, accessed through voltage fluctuation measurements in current-biased samples. The measured Lorentzian spectrum of the R-fluctuations identifies their correlation time, which is shown to coincide with the thermal relaxation time determined by a combination of the electron-phonon relaxation and the diffusion in reservoirs. Our data is quantitatively consistent with the model of spontaneous temperature fluctuations, the Tfluctuations, with a variance given by the textbook thermodynamic expression. We discuss the experimental indication that the T-fluctuations contribute to the broadening of the transition, in spite of vanishing in the limit of infinite sample volume. Our observations highlight important caveats in the accepted physical picture of the resistive transition.
E.M. Baeva, A.I. Kolbatova, N.A. Titova, S. Saha, A. Boltasseva, S.I. Bogdanov, V.M. Shalaev, A.V. Semenov, A. Levchenko, G.N. Goltsman, and V.S. Khrapai, preprint available on arXiv at https://arxiv.org/pdf/2202.06309
One of the main characteristics of optical imaging systems is the spatial resolution, which is restricted by the diffraction limit to approximately half the wavelength of the incident light. Along with the recently developed classical superresolution techniques, which aim at breaking the diffraction limit in classical systems, there is a class of quantum super-resolution techniques which leverage the non-classical nature of the optical signals radiated by quantum emitters, the so called antibunching super-resolution microscopy. This approach can ensure a factor of √𝑛 improvement in the spatial resolution by measuring the 𝑛 -th order autocorrelation function. The main bottleneck of the antibunching super-resolution microscopy is the time-consuming acquisition of multi-photon event histograms. We present a machine learning-assisted approach for the realization of rapid antibunching super-resolution imaging and demonstrate 12 times speed-up compared to conventional, fitting-based autocorrelation measurements. The developed framework paves the way to the practical realization of scalable quantum super-resolution imaging devices that can be compatible with various types of quantum emitters.
Z.A. Kudyshev, D. Sychev, Z.O. Martin, S.I. Bogdanov, X. Xu, A.V. Kildishev, A. Boltasseva and V.M. Shalaev, preprint available on arXiv at https://arxiv.org/abs/2107.02401
Quantum emitters coupled to plasmonic nanoantennas produce single photons at unprecedentedly high rates in ambient conditions. This enhancement of quantum emitters’ radiation rate is based on the existence of optical modes with highly sub-diffraction volumes supported by plasmonic gap-nanoantennas. Nanoantennas with gap sizes on the order of few nanometers have been typically produced using various self-assembly or random assembly techniques. Yet, the difficulty of controllably fabricate nanoantennas with the smallest mode sizes coupled to pre-characterized single emitters until now has remained a serious issue plaguing the development of quantum plasmonic devices. We demonstrate the transfer of nanodiamonds with single nitrogen-vacancy (NV) centers to an epitaxial silver substrate and their subsequent deterministic coupling to plasmonic gap nanoantennas. Through fine control of the assembled nanoantenna geometry, a dramatic shortening of the NV fluorescence lifetime was achieved. We furthermore show that by preselecting NV centers exhibiting a photostable spin contrast, a coherent spin dynamics can be measured in the coupled configuration. The demonstrated approach opens unique applications of plasmon-enhanced quantum emitters for integrated quantum information and sensing devices.
S.I. Bogdanov, O.A. Makarova, A.S. Lagutchev, D. Shah, C.-C. Chiang, S. Saha, A.S. Baburin, I.A. Ryzhikov, I.A. Rodionov, A.V. Kildishev, A. Boltasseva and V.M. Shalaev, preprint available on arXiv at http://arxiv.org/abs/1902.05996
The nanoscale magnetic field of magnons has emerged as a promising resource for coherently driving qubits such as quantum spin defects (QSD) and developing versatile probes for magnetism and other types of quantum matter. Tuning this coupling via electric field would provide a path to address the outstanding challenges of enhancing QSD-based sensing of electric fields and locally manipulating QSD qubits with minimal power. Here, we demonstrate a new approach to such electric field tuning using a ferromagnet-ferroelectric hybrid multiferroic film integrated with nitrogen-vacancy (NV) center spins. Combining NV-spin relaxometry with ferromagnetic resonance measurements, we reveal that the ferroelectric polarization controls the magnetic anisotropy, which tunes the magnon-generated fields at the NVs. Flipping the ferroelectric polarization changes NV-spin relaxation rate by 400%, which could be further enhanced by three orders of magnitude by nanopatterning the ferromagnets. Our results offer possibilities of realizing improved NV-sensing of electric fields, electric-field-tunable quantum spintronic devices, and magnon/spin probes of the multiferroic order and quantum materials.
A.B. Solanki, S.I. Bogdanov, M.M. Rahman, A. Rustagi, N.R. Dilley, T. Shen, W. Tong, P. Debashis, Z. Chen, J. Appenzeller, Y.P. Chen, V.M. Shalaev and P. Upadhyaya, Phys. Rev. Research, 4, L012025 (2022)
22. Rapid absolute sizing of deeply subwavelength dielectric nanoparticles by confocal scanning optical microscopy
Accurate sizing of individual nanoparticles is crucial for the understanding of their physical and chemical properties, and for their use in nanoscale devices. Optical sizing methods are noninvasive, rapid and versatile. However, the low optical response of weakly absorbing subwavelength dielectric nanoparticles poses a fundamental challenge for their optical metrology. We demonstrate scalable optical sizing of such nanoparticles based on confocal scanning microscopy. The method is absolutely calibrated by correlating the optical signatures in the scattered pump laser signal to the ground truth nanoparticle sizes measured by an atomic force microscope. Using an air objective with a numerical aperture of 0.9, we measured the sizes of nanodiamond particles ranging from 35 to 175 nm, with an average error of ± 12.7 nm compared to the ground truth sizes. This technique paves the way for the metrology of a wide range of weakly scattering nano-objects for applications in biomedicine, catalysis, nanotechnology and quantum optics.
S. Sahoo, H. Azzouz and S.I. Bogdanov, Appl. Phys. Lett. 118, 241105 (2021)
Rapid and deterministic nanoscale assembly of quantum emitters remains a daunting challenge for the realization of practical, on-chip quantum photonic devices. The major bottleneck is the time-consuming second-order photon autocorrelation measurements for the classification of solid-state quantum emitters into “single” and “non-single” photon sources during the quantum device assembly. We have adapted supervised machine learning algorithms to perform such classification in an efficient sub-second process based on sparse autocorrelation data. We demonstrate an ~80% fidelity of emitter classification based on datasets containing on average only one co-detection event per bin. In contrast, the conventional fitting classification method based on Levenberg-Marquardt fitting typically requires two-orders of magnitude longer collection times, and it fails entirely when applied to the same datasets. We anticipate that machine learning-based classification will provide a unique route to enable rapid and scalable assembly of quantum nanophotonic devices and can be directly extended to other quantum optical measurements, promising breakthroughs in quantum information, sensing and super-resolution microscopy.
Z.A. Kudyshev, S.I. Bogdanov, T. Isacsson, A.V. Kildishev, A. Boltasseva and V. M. Shalaev, Adv. Quant. Technol., 3, 2000067 (2020)
On-chip scalable integration represents a major challenge for practical quantum devices. One particular challenge is to implement on-chip optical readout of spins in diamond. This readout requires simultaneous application of optical and microwave fields along with an efficient collection of fluorescence. The readout is typically accomplished via bulk optics and macroscopic microwave transmission structures. We experimentally demonstrate an on-chip integrated structure for nitrogen‑vacancy (NV) spin-based applications, implemented in a single material layer with one patterning step. A nanodiamond with multiple NV centers is positioned at the end of the groove waveguide milled in a thick gold film. The gold film carries the microwave control signal while the groove waveguide acts as a fluorescence collector, partially filtering out the pump excitation. As a result, the device dimensions and fabrication complexity are substantially reduced. Our approach will foster further development of ultra-compact nanoscale quantum sensors and quantum information processing devices on a monolithic platform. NV center-based nanoscale sensors are the most promising application of the developed interface.
M. Y. Shalaginov, S. I. Bogdanov, A. S. Lagutchev, A. V. Kildishev, A. Boltasseva, and V. M. Shalaev, ACS Photonics 7, 2018 (2020)
Integrated on-demand single-photon sources are critical for the implementation of photonic quantum information processing systems. To enable practical quantum photonic devices, the emission rates of solid-state quantum emitters need to be substantially enhanced and the emitted signal must be directly coupled to an on-chip circuitry. The photon emission rate speed-up is best achieved via coupling to plasmonic antennas, while on-chip integration can be easily obtained by directly coupling emitters to photonic waveguides. The realization of practical devices requires that both the emission speed-up and efficient out-coupling are achieved in a single architecture. Here, we propose a novel platform that effectively combines on-chip compatibility with high radiative emission rates, a quantum plasmonic launcher. The proposed launchers contain single nitrogen-vacancy (NV) centers in nanodiamonds as quantum emitters that offer record-high average fluorescence lifetime shortening factors of about 7000 times. Nanodiamonds with single NV are sandwiched between two silver films that couple more than half of the emission into in-plane propagating surface plasmon polaritons. This simple, compact, and scalable architecture represents a crucial step towards the practical realization of high-speed on-chip quantum networks.
C.-C. Chiang, S. I. Bogdanov, O. A. Makarova, X. Xu, S. Saha, D. Shah, D. Wang, A. S. Lagutchev, A. V. Kildishev, A. Boltasseva, and V. M. Shalaev, Adv. Opt. Mater., 8 2000889 (2020)
18. Ultrafast quantum photonics enabled by coupling plasmonic nanocavities to strongly radiative antennas
Quantum emitters coupled to plasmonic nanostructures can act as exceptionally bright sources of single photons. Plasmonic mode volumes supported by these nanostructures can be several orders of magnitude smaller than the cubic wavelength, which leads to dramatically enhanced light-matter interactions and drastically increased photon production rates. However, when increasing the light localization further, these deeply subwavelength modes may in turn hinder the fast outcoupling of photons into the free space. Plasmonic hybrid nanostructures combining a highly confined cavity mode and a larger antenna mode circumvent this issue. We establish the fundamental limits for quantum emission enhancement in such systems and find that the best performance is achieved when the cavity and antenna modes differ significantly in size. We experimentally support this idea by photomodifying a single-photon nanopatch antenna deterministically assembled around a nanodiamond known to contain a single nitrogen-vacancy (NV) center. As a result, the cavity mode shrinks, further shortening the NV fluorescence lifetime and increasing the single-photon brightness. Our analytical and numerical simulation results provide an intuitive insight into the operation of these emitter-cavity-antenna systems and show that this approach could lead to single-photon sources with emission rates up to hundreds of THz and efficiencies close to unity.
S.I. Bogdanov, O.A. Makarova, X. Xu, Z.O. Martin, A.S. Lagutchev, M. Olinde, D. Shah, S.N. Chowdhuri, A.R. Gabidullin, I.A. Ryzhikov, I.A. Rodionov, A.V. Kildishev, S.I. Bozhevolnyi, A. Boltasseva, V.M. Shalaev and J.B. Khurgin, Optica, 7, 463 (2020)
We analyze the evolution of the normal and superconducting electronic properties in epitaxial TiN films as a function of the film thickness with high Ioffe-Regel parameter values. As the film thickness decreases, we observe an increase in the residual resistivity, which becomes dominated by diffusive surface scattering for d ≤ 20nm. At the same time, a substantial thickness-dependent reduction of the superconducting critical temperature is observed compared to the bulk TiN value. In such high-quality material films, this effect can be explained by a weak magnetic disorder residing in the surface layer. Our results suggest that surface magnetic disorder is generally present in oxidized TiN films.
N.A. Tovpeko, N.A. Titova, E.M. Baeva, A.V. Semenov, S. Saha, H. Reddy, S. Bogdanov, E.E. Marinero, V.M. Shalaev, A. Boltasseva, V.S. Khrapai, A.I. Kardakova, and G.N. Goltsman, Phys. Rev. Applied 12, 054001 (2019)
Single photons are the most suitable carriers of information for the implementation of quantum networks. Most optical quantum information scenarios require that photons be “coherent” or indistinguishable. Loss of coherence often occurs when light interacts with matter, which is needed to produce single photons and perform logical operations on them. One way to combat optical decoherence is to suppress noise in matter e.g. through cryogenic cooling. A targeted use of plasmonics (i.e. metal-based photonics) offers a different, arguably more attractive path. In this Perspective, we discuss the approach to achieve quantum optical coherence by dramatically speeding up light-matter interaction. We also outline strategies to minimize photon losses in metals.
S.I. Bogdanov, A. Boltasseva and V.M. Shalaev, Science, 364, 532 (2019)
15. Ultrabright room-temperature sub-nanosecond emission from single nitrogen-vacancy centers coupled to nano-patch antennas
Single-photon emitters are intrinsically dim because they emit photons one by one, and these photons are separated on average by the characteristic time of spontaneous decay – the fluorescence lifetime. Using plasmonic nanoantennas, it is possible to shorten this lifetime by 100 or even 1000 times, which could make the emitters brighter. However, optical absorption in most plasmonic materials is several orders of magnitude stronger than in dielectrics. As a result, the increase in brightness in plasmonic nanoantennas has been far behind what the lifetime shortening suggests: most of the emission ends up being absorbed and never makes it into the far-field. We have employed epitaxial silver films with record-low losses from our collaborators in Moscow, Russia and crystalline silver nanocubes to fabricate single-photon nanoantennas. We used photostable nitrogen-vacancy centers in diamond as single-photon emitters. The resulting sources of single photons emit tens of millions of photons per second, making them the brightest ones operating at room temperature.
S.I. Bogdanov, M.Y. Shalaginov, A.S. Lagutchev, C.-C. Chiang, D. Shah, A.S. Baburin, I.A. Ryzhikov, I.A. Rodionov, A.V. Kildishev, A. Boltasseva, and V.M. Shalaev, Nano Letters, 18, 4837 (2018)
The fluorescence of nanoscale quantum emitters is intrinsically isotropic and therefore difficult to harvest. We have fabricated a plasmonic antenna consisting of an unprocessed flat protected silver layer and a bulls-eye titania grating. Using an AFM tip, we have placed a nanodiamond containing a nitrogen-vacancy center ensemble (NVE) into the center of the antenna. As a result, we have obtained highly directional (< 10° half-angle) emission from the NVE in a broad (600-700 nm) wavelength range.
S.K.H. Andersen, S. Bogdanov, Y. Xuan, O. Makarova, M.Y. Shalaginov, A. Boltasseva, V.M. Shalaev and S. Bozhevolnyi, ACS Photonics, 5, 692 (2018)
13. Patterned multilayer metamaterial for fast and efficient photon collection from dipolar emitters
The coupling of nanoscale optical emitters to a planar hyperbolic metamaterial results in a significant Purcell enhancement in a very broad wavelength range, unlike in the case of resonant antennas. However, in this case, most of the enhanced emission is lost inside the metamaterial, leading to poor collection efficiency (< 1% for the out-of-plane dipoles). To circumvent this issue, we numerically show that a simple circular corrugation in the metamaterial layer can improve the collection efficiency by 10 to 50 times from arbitrarily oriented dipoles and in a broad wavelength range (600-800 nm).
O.A. Makarova, M.Y. Shalaginov, S. Bogdanov, U. Guler, A. Boltasseva, A.V. Kildishev and V.M. Shalaev, Optics Letters 42, 3968 (2017)
Nitrogen-vacancy centers in diamond allow for coherent spin-state manipulation at room temperature, which could bring dramatic advances to nanoscale sensing and quantum information technology. We introduce a method for the optical measurement of the spin contrast in dense nitrogen-vacancy (NV) ensembles. This method brings insight into the interplay between the spin contrast and fluorescence lifetime. We show that for improving the spin readout sensitivity in NV ensembles, one should aim at modifying the far-field radiation pattern rather than
enhancing the emission rate.
S. Bogdanov, M.Y. Shalaginov, P. Kapitanova, J. Liu, M. Ferrera, A. Lagutchev, P. Belov, J. Irudayaraj, A. Boltasseva and V. Shalaev, Physical Review B 96, 035146 (2017)
On-chip integration of quantum optical systems could be a major factor enabling photonic quantum technologies. While III-V materials have been shown to host most quantum photonic components, the issues of their intercompatibility, scalability and performance are far from being solved. Therefore, many material platforms are being examined to host the future quantum photonic computers and network nodes. We discuss the pros and cons of several platforms for realizing various elementary devices, compare the current degrees of integration achieved in each platform and review several composite platform approaches.
S. Bogdanov, M.Y. Shalaginov, A. Boltasseva and V.M. Shalaev, Optical Materials Express 7, 111 (2017)
10. Antimonide-based type-II superlattices – a superior candidate for the third generation of infarared imaging systems
Type II superlattices (T2SLs), a system of interacting multiquantum wells, were introduced by Nobel Laureate L. Esaki in the 1970s. Since then, this material system has drawn a lot of attention, especially for infrared detection and imaging. We present the current status of T2SL-based photodetectors and FPAs for imaging in different infrared regimes, from short wavelength to very long wavelength, and dual-band infrared detection and imaging, as well as the future outlook for this material system.
M. Razeghi, A. Haddadi, A.M. Hoang, G. Chen, S. Bogdanov, S.R. Darvish, F. Callewaert, P.R. Bijjam and R. McClintock, Journal of Electronic Materials 43(8), 2802 (2014)
9. Effect of sidewall surface recombination on the quantum efficiency in a Y2O3 passivated gated type-II InAs/GaSb long-infrared photodetector array
G. Chen, A.M. Hoang, S. Bogdanov, A. Haddadi, S.R. Darvish and M. Razeghi, Applied Physics Letters 103, 223501 (2013).
G. Chen, A.M. Hoang, S. Bogdanov, P.R. Bijjam, B.-M. Nguyen and M. Razeghi, Applied Physics Letters 103, 033512 (2013).
7. Surface leakage investigation via gated type-II InAs/GaSb long-wavelength infrared photodetectors
G. Chen, E.K. Huang, A.M. Hoang, S. Bogdanov, S.R. Darvish and M. Razeghi, Applied Physics Letters 101, 213501 (2012).
6. Advances in antimonide-based Type-II superlattices for infrared detection and imaging at the center for quantum devices
M. Razeghi, A. Haddadi, A.M. Hoang, E.K. Huang, G. Chen, S. Bogdanov, S.R. Darvish, F. Callewaert and R. McClintock, Infrared Physics and Technology, 59, 41 (2012).
B.M. Nguyen, G. Chen, A.M. Hoang, S. Abdollahi Pour, S. Bogdanov, and M. Razeghi, Applied Physics Letters 99, 033501 (2011).
4. Surface leakage current reduction in long wavelength infrared type-II InAs/GaSb superlattice photodiodes
S. Bogdanov, B.M. Nguyen, A.M. Hoang and M. Razeghi, Applied Physics Letters 98, 183501 (2011).
3. Minority electron unipolar photodetectors based on type II InAs/GaSb/AlSb superlattices for very long wavelength infrared detection
B.M. Nguyen, S. Bogdanov, S. Abdollahi Pour, and M. Razeghi, Applied Physics Letters 95, 183502 (2009).
2. Demonstration of high performance long wavelength infrared type II InAs/GaSb superlattice photodiode grown on GaAs substrate
S. Abdollahi Pour, B.M. Nguyen, S. Bogdanov, E.K. Huang, and M. Razeghi, Applied Physics Letters 95, 173505 (2009).
B.M. Nguyen, D. Hoffman, E.K. Huang, S. Bogdanov, P.Y. Delaunay, M. Razeghi and M.Z. Tidrow, Applied Physics Letters 94, 223506 (2009).