Nanoscale Optical Trapping: A Review

© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Optical trapping is the craft of manipulating objects with light. Decades after its first inception in 1970, the technique has become a powerful tool for ultracold-atom physics and manipulation of micron-sized particles. Yet, optical trapping of objects at the intermediate—nanoscale—range is still beyond full grasp. This matters because the nanometric realm is where several promising advances, from mastering single-molecule experiments in biology, to fabricating hybrid devices for nanoelectronics and photonics, as well as testing fundamental quantum phenomena in optomechanics, are anticipated to produce impactful breakthroughs. After a comprehensive, theoretical introduction to the phenomenon of optical trapping, this review delves into assessing the current state-of-the-art for optical manipulation of objects at the nanoscale. Emphasis is put on presenting the challenges that coalesced into driving the field to its current development, as well as discussing the outstanding barriers, which might lead to future advancements in the field

Efficient characterization of blinking quantum emitters from scarce data sets via machine learning

Single photon emitters are core building blocks of quantum technologies, with established and emerging applications ranging from quantum computing and communication to metrology and sensing. Regardless of their nature, quantum emitters universally display fluorescence intermittency or photoblinking: interaction with the environment can cause the emitters to undergo quantum jumps between on and off states that correlate with higher and lower photoemission events, respectively. Understanding and quantifying the mechanism and dynamics of photoblinking is important for both fundamental and practical reasons. However, the analysis of blinking time traces is often afflicted by data scarcity. Blinking emitters can photo-bleach and cease to fluoresce over time scales that are too short for their photodynamics to be captured by traditional statistical methods. Here, we demonstrate two approaches based on machine learning that directly address this problem. We present a multi-feature regression algorithm and a genetic algorithm that allow for the extraction of blinking on/off switching rates with >85% accuracy, and with >10x less data and >20x higher precision than traditional methods based on statistical inference. Our algorithms effectively extend the range of surveyable blinking systems and trapping dynamics to those that would otherwise be considered too short-lived to be investigated. They are therefore a powerful tool to help gain a better understanding of the physical mechanism of photoblinking, with practical benefits for applications based on quantum emitters that rely on either mitigating or harnessing the phenomenon

Effect of structure and composition of nanodiamond powders on thermal stability and oxidation kinetics

© 2018 Elsevier Ltd Oxidation has been suggested as an effective and scalable means for industrial purification of nanodiamond (ND) powders. However, conflicting accounts were reported with respect to oxidation behavior of commercial powders and the temperature range in which non-diamond phases can be removed efficiently. In this study, we investigate the effects of composition and structural characteristics of ND on the oxidation kinetics. The effect of crystal size was analyzed by directly measure the oxidation behavior of individual ND crystal in the size range 2–20 nm, probing the size-dependence of the oxidation kinetics at the lower end of the nanoscale. This study also leads to the first experimental data on the minimum size at which ND crystals become thermodynamically unstable and cease to exist as well as the minimum size of a luminescent ND still hosting an optically active nitrogen-vacancy (NV) center

Photoinduced blinking in a solid-state quantum system

© 2017 American Physical Society. Solid-state single-photon emitters (SPEs) are one of the prime components of many quantum nanophotonics devices. In this work, we report on an unusual, photoinduced blinking phenomenon of SPEs in gallium nitride. This is shown to be due to the modification in the transition kinetics of the emitter, via the introduction of additional laser-activated states. We investigate and characterize the blinking effect on the brightness of the source and the statistics of the emitted photons. Combining second-order correlation and fluorescence trajectory measurements, we determine the photodynamics of the trap states and characterize power-dependent decay rates and characteristic "off"-time blinking. Our work sheds light into understanding solid-state quantum system dynamics and, specifically, power-induced blinking phenomena in SPEs

High-Resolution Optical Imaging and Sensing Using Quantum Emitters in Hexagonal Boron-Nitride

Super-resolution microscopy has allowed optical imaging to reach resolutions well beyond the limit imposed by the diffraction of light. The advancement of super-resolution techniques is often an application-driven endeavor. However, progress in material science plays a central role too, as it allows for the synthesis and engineering of nanomaterials with the unique chemical and physical properties required to realize super-resolution imaging strategies. This aspect is the focus of this review. We show that quantum emitters in two-dimensional hexagonal boron nitride are proving to be excellent candidate systems for the realization of advanced high-resolution imaging techniques, and spin-based quantum sensing applications

Silver Columnar Thin-Film-Based Half-Wavelength Antennas for Bright Directional Emission from Nanodiamond Nitrogen-Vacancy Centers

© 2019 American Physical Society. Nitrogen-vacancy (N-V) centers in nanodiamond (ND) are a promising single-photon-source candidate for quantum technology. However, the poor N-V emission rate and low outcoupling of light significantly hinder their effective use in practical implementations. To overcome this limit, we place NDs hosting N-V centers on silver columnar thin films (CTFs) and measure an increase in emission by an order of magnitude. The CTFs consist of silver nanocolumns the length of which is chosen to be half the wavelength of the emitted light. The silver nanocolumns act as efficient optical antennas that couple to the N-V centers via the optical near field and outcouple the excitation energy of the N-V centers effectively into the optical far field. A large distribution of radiated powers from different NDs is observed. Computer simulations show this distribution to arise from the different orientations of the emitting dipoles with respect to the columnar axis. We also report that further structuring of the silver CTF into gratings yields higher photon emission

Non-intrusive tunable resonant microwave cavity for optical detected magnetic resonance of NV centres in nanodiamonds

Optically detected magnetic resonance (ODMR) in nanodiamond nitrogen-vacancy (NV) centres is usually achieved by applying a microwave field delivered by micron-size wires, strips or antennas directly positioned in very close proximity (∼ μm) of the nanodiamond crystals. The microwave field couples evanescently with the ground state spin transition of the NV centre (2.87 GHz at zero magnetic field), which results in a reduction of the centre photoluminescence. We propose an alternative approach based on the construction of a dielectric resonator. We show that such a resonator allows for the efficient detection of NV spins in nanodiamonds without the constraints associated to the laborious positioning of the microwave antenna next to the nanodiamonds, providing therefore improved flexibility. The resonator is based on a tunable Transverse Electric Mode in a dielectric-loaded cavity, and we demonstrate that the resonator can detect single NV centre spins in nanodiamonds using less microwave power than alternative techniques in a non-intrusive manner. This method can achieve higher precision measurement of ODMR of paramagnetic defects spin transition in the micro to millimetre-wave frequency domain. Our approach would permit the tracking of NV centres in biological solutions rather than simply on the surface, which is desirable in light of the recently proposed applications of using nanodiamonds containing NV centres for spin labelling in biological systems with single spin and single particle resolution. © 2013 Copyright SPIE

Asymmetric Gravitational Lenses in TeVeS and Application to the Bullet Cluster

Aims: We explore the lensing properties of asymmetric matter density distributions in Bekenstein's Tensor-Vector-Scalar theory (TeVeS). Methods: Using an iterative Fourier-based solver for the resulting non-linear scalar field equation, we numerically calculate the total gravitational potential and derive the corresponding TeVeS lensing maps. Results: Considering variations on rather small scales, we show that the lensing properties significantly depend on the lens's extent along the line of sight. Furthermore, all simulated TeVeS convergence maps strongly track the dominant baryonic components, non-linear effects, being capable of counteracting this trend, turn out to be very small. Setting up a toy model for the cluster merger 1E0657-558, we infer that TeVeS cannot explain observations without assuming an additional dark mass component in both cluster centers, which is in accordance with previous work.Comment: LaTex, 14 pages, 10 figures, references added, 2 figures removed, minor text changes to fit accepted version (A&A