arXiv subjects

Igor Aharonovich

Publications and source records attributed to Igor Aharonovich.

At least 145 records · Page 8Linked to original sources

arXiv2018

Very Large and Reversible Stark Shift Tuning of Single Emitters in Layered Hexagonal Boron Nitride

Combining solid state single photon emitters (SPE) with nanophotonic platforms is a key goal in integrated quantum photonics. In order to realize functionality in potentially scalable elements, suitable SPEs have to be bright, stable, and widely tunable at room temperature. In this work we show that selected SPEs embedded in a few layer hexagonal boron nitride (hBN) meet these demands. In order to show the wide tunability of these SPEs we employ an AFM with a conductive tip to apply an electrostatic field to individual hBN emitters sandwiched between the tip and an indium tin oxide coated glass slide. A very large and reversible Stark shift of $(5.5 \pm 3)\,$nm at a zero field wavelength of $670\,$nm was induced by applying just $20\,$V, which exceeds the typical resonance linewidths of nanodielectric and even nanoplasmonic resonators. Our results are important to further understand the physical origin of SPEs in hBN as well as for practical quantum photonic applications where wide spectral tuning and on/off resonance switching are required.

cond-mat.mes-hall↗

arXiv2018

Effects of microstructure and growth conditions on quantum emitters in Gallium Nitride

Single-photon emitters in gallium nitride (GaN) are gaining interest as attractive quantum systems due to the well-established techniques for growth and nanofabrication of the host material, as well as its remarkable chemical stability and optoelectronic properties. We investigate the nature of such single-photon emitters in GaN with a systematic analysis of various samples produced under different growth conditions. We explore the effect that intrinsic structural defects (dislocations and stacking faults), doping and crystal orientation in GaN have on the formation of quantum emitters. We investigate the relationship between the position of the emitters (determined via spectroscopy and photoluminescence measurements) and the location of threading dislocations (characterised both via atomic force microscopy and cathodoluminescence). We find that quantum emitters do not correlate with stacking faults or dislocations; instead, they are more likely to originate from point defects or impurities whose density is modulated by the local extended defect density.

physics.app-ph↗

arXiv2018

Anti-Stokes excitation of solid-state quantum emitters for nanoscale thermometry

Color centers in solids are the fundamental constituents of a plethora of applications such as lasers, light emitting diodes and sensors, as well as the foundation of advanced quantum information and communication technologies. Their photoluminescence properties are usually studied under Stokes excitation, in which the emitted photons are at a lower energy than the excitation ones. In this work, we explore the opposite Anti-Stokes process, where excitation is performed with lower energy photons. We report that the process is sufficiently efficient to excite even a single quantum system, namely the germanium-vacancy center in diamond. Consequently, we leverage the temperature-dependent, phonon-assisted mechanism to realize an all-optical nanoscale thermometry scheme that outperforms any homologous optical method employed to date. Our results frame a promising approach for exploring fundamental light-matter interactions in isolated quantum systems, and harness it towards the realization of practical nanoscale thermometry and sensing.

physics.app-ph↗

arXiv2018

Fabrication of photonic nanostructures from hexagonal boron nitride

Growing interest in devices based on layered van der Waals (vdW) materials is motivating the development of new nanofabrication methods. Hexagonal boron nitride (hBN) is one of the most promising materials for studies of quantum photonics and polaritonics. Here, we report in detail on a promising nanofabrication processes used to fabricate several hBN photonic devices using a hybrid electron beam induced etching (EBIE) and reactive ion etching (RIE) technique. We highlight the shortcomings and benefits of RIE and EBIE and demonstrate the utility of the hybrid approach for the fabrication of suspended and supported device structures with nanoscale features and highly vertical sidewalls. Functionality of the fabricated devices is proven by measurements of high quality cavity optical modes (Q~1500). Our nanofabrication approach constitutes an advance towards an integrated, monolithic quantum photonics platform based on hBN and other layered vdW materials.

physics.app-ph↗

arXiv2018

A random laser based on diamond nanoneedles

Random lasers use radiative gain and multiple scatterers in disordered media to generate light amplification. In this study, we demonstrate a random laser based on diamond nanoneedles that act as scatterers in combination with fluorescent dye molecules that serve as a gain medium. Random lasers realized using diamond possess high spectral radiance with angle-free emission and thresholds of 0.16 mJ. The emission dependence on the pillar diameter and density is investigated, and optimum lasing conditions are measured for pillars with spacing and density of 336 nm and ~ 2.9x10^10 cm-2. Our results expand the application space of diamond as a material platform for practical, compact photonic devices and sensing applications.

physics.optics↗

arXiv2018

Internal nanostructure diagnosis with hyperbolic phonon polaritons in hexagonal boron nitride

Imaging materials and inner structures with resolution below the diffraction limit has become of fundamental importance in recent years for a wide variety of applications. In this work, we report sub-diffractive internal structure diagnosis of hexagonal boron nitride by exciting and imaging hyperbolic phonon polaritons. Based on their unique propagation properties, we are able to accurately locate defects in the crystal interior with nanometer resolution. The precise location, size and geometry of the concealed defects is reconstructed by analyzing the polariton wavelength, reflection coefficient and their dispersion. We have also studied the evolution of polariton reflection, transmission and scattering as a function of defect size and photon frequency. The nondestructive high-precision polaritonic structure diagnosis technique introduced here can be also applied to other hyperbolic or waveguide systems, and may be deployed in the next-generation bio-medical imaging, sensing and fine structure analysis.

cond-mat.mes-hall↗

arXiv2018

Enhanced Emission from WSe2 Monolayers Coupled to Circular Bragg Gratings

Two-dimensional transition-metal dichalcogenides (TMDC) are of great interest for on-chip nanophotonics due to their unique optoelectronic properties. Here, we propose and realize coupling of tungsten diselenide (WSe2) monolayers to circular Bragg grating structures to achieve enhanced emission. The interaction between WSe2 and the resonant mode of the structure results in Purcell-enhanced emission, while the symmetric geometrical structure improves the directionality of the out-coupling stream of emitted photons. Furthermore, this hybrid structure produces a record high contrast of the spin valley readout (> 40%) revealed by the polarization resolved photoluminescence (PL) measurements. Our results are promising for on-chip integration of TMDC monolayers with optical resonators for nanophotonic circuits.

physics.optics↗

arXiv2018

Bottom up engineering of near-identical quantum emitters in atomically thin materials

Quantum technologies require robust and photostable single photon emitters (SPEs) that can be reliably engineered. Hexagonal boron nitride (hBN) has recently emerged as a promising candidate host to bright and optically stable SPEs operating at room temperature. However, the emission wavelength of the fluorescent defects in hBN has, to date, been shown to be uncontrolled. The emitters usually display a large spread of zero phonon line (ZPL) energies spanning over a broad spectral range (hundreds of nanometers), which hinders the potential development of hBN-based devices and applications. We demonstrate bottom-up, chemical vapor deposition growth of large-area, few layer hBN that hosts large quantities of SPEs: 100 per 10x10 μm2. Remarkably, more than 85 percent of the emitters have a ZPL at (580{\pm}10)nm, a distribution which is over an order of magnitude narrower than previously reported. Exploiting the high density and uniformity of the emitters, we demonstrate electrical modulation and tuning of the ZPL emission wavelength by up to 15 nm. Our results constitute a definite advancement towards the practical deployment of hBN single photon emitters in scalable quantum photonic and hybrid optoelectronic devices based on 2D materials.

physics.app-ph↗

arXiv2018

Effects of high energy electron irradiation on quantum emitters in hexagonal boron nitride

Hexagonal Boron Nitride (hBN) mono and multilayers are promising hosts for room temperature single photon emitters (SPEs). In this work we explore high energy (~ MeV) electron irradiation as a means to generate stable SPEs in hBN. We investigate four types of exfoliated hBN flakes - namely, high purity multilayers, isotopically pure hBN, carbon rich hBN multilayers and monolayered material - and find that electron irradiation increases emitter concentrations dramatically in all samples. Furthermore, the engineered emitters are located throughout hBN flakes (not only at flake edges or grain boundaries), and do not require activation by high temperature annealing of the host material after electron exposure. Our results provide important insights into controlled formation of hBN SPEs and may aid in identification of their crystallographic origin.

cond-mat.mtrl-sci↗

arXiv2018

Single crystal diamond membranes containing germanium vacancy color centers

Single crystal diamond membranes that host optically active emitters are highly attractive components for integrated quantum nanophotonics. In this work we demonstrate bottom-up synthesis of single crystal diamond membranes containing the germanium vacancy (GeV) color centers. We employ a lift-off technique to generate the membranes and perform chemical vapour deposition in a presence of germanium oxide to realize the insitu doping. Finally, we show that these membranes are suitable for engineering of photonic resonators such as microring cavities with quality factors of 1500. The robust and scalable approach to engineer single crystal diamond membranes containing emerging color centers is a promising pathway for realization of diamond integrated quantum nanophotonic circuits on a chip.

physics.optics↗

arXiv2018

Photonic Crystal Cavities from Hexagonal Boron Nitride

Development of scalable quantum photonic technologies requires on-chip integration of components such as photonic crystal cavities and waveguides with nonclassical light sources. Recently, hexagonal boron nitride (hBN) has emerged as a promising platform for nanophotonics, following reports of hyperbolic phonon-polaritons and optically stable, ultra-bright quantum emitters. However, exploitation of hBN in scalable, on-chip nanophotonic circuits, quantum information processing and cavity quantum electrodynamics (QED) experiments requires robust techniques for the fabrication of monolithic optical resonators. In this letter, we design and engineer high quality photonic crystal cavities from hBN. We employ two approaches based on a focused ion beam method and a minimally-invasive electron beam induced etching (EBIE) technique to fabricate suspended two dimensional (2D) and one dimensional (1D) cavities with quality (Q) factors in excess of 2,000. Subsequently, we show deterministic, iterative tuning of individual cavities by direct-write, single-step EBIE without significant degradation of the Q-factor. The demonstration of tunable, high Q cavities made from hBN is an unprecedented advance in nanophotonics based on van der Waals materials. Our results and hBN processing methods open up promising new avenues for solid-state systems with applications in integrated quantum photonics, polaritonics and cavity QED experiments.

physics.app-ph↗

arXiv2017

Single Photon Emission from Plasma Treated 2D Hexagonal Boron Nitride

Artificial atomic systems in solids are becoming increasingly important building blocks in quantum information processing and scalable quantum nanophotonic networks. Yet, synthesis of color centers that act as single photon emitters which are suitable for on-chip applications is still beyond reach. Here, we report a number of plasma and thermal annealing methods for the fabrication of emitters in tape-exfoliated hexagonal boron nitride (hBN) crystals. A two-step process comprised of Ar plasma etching and subsequent annealing in Ar is highly robust, and yields a seven-fold increase in the concentration of emitters in hBN. The initial plasma etching step generates emitters that suffer from blinking and bleaching, whereas the two-step process yields emitters that are photostable at room temperature and have an emission energy distribution that is red-shifted relative to that of pristine hBN. An analysis of emitters fabricated by a range of plasma and annealing treatments, combined with a theoretical investigation of point defects in hBN indicates that single photon emitters characterized by a high degree of photostability and emission wavelengths greater than ~700 nm are associated with defect complexes that contain oxygen. This is further confirmed by generating the emitters by annealing hBN in an oxidative atmosphere. Our findings advance present understanding of the structure of quantum emitter in hBN and enhance the nanofabrication toolkit that is needed to realize integrated quantum nanophotonics based on 2D materials.

cond-mat.mtrl-sci↗

arXiv2017

Nanoassembly of quantum emitters in hexagonal boron nitride and gold nanospheres

Assembly of quantum nanophotonic systems with plasmonic resonators are important for fundamental studies of single photon sources as well as for on-chip information processing. In this work, we demonstrate controllable nanoassembly of gold nanospheres with ultra-bright quantum emitters in 2D layered hexagonal boron nitride (hBN). We utilize an atomic force microscope (AFM) tip to precisely position gold nanospheres to close proximity of the quantum emitters and observe the resulting emission enhancement and fluorescence lifetime reduction. A fluorescence enhancement of over 300% is achieved experimentally for quantum emitters in hBN, with a radiative quantum efficiency of up to 40% and a saturated count rate in excess of 5 million counts/s. Our results are promising for future employment of quantum emitters in hBN for integrated nanophotonic devices and plasmonic based nanosensors.

physics.optics↗

arXiv2017

Super-resolution imaging of quantum emitters in layered materials

Layered van der Waals materials are emerging as compelling two-dimensional (2D) platforms for studies of nanophotonics, polaritonics, valleytronics and spintronics, and have the potential to transform applications in sensing, imaging and quantum information processing. Amongst these, hexagonal boron nitride (hBN) is unique in that it hosts ultra-bright, room temperature single photon emitters (SPEs). However, an outstanding challenge is to locate SPEs in hBN with high precision, a task which requires breaking the optical diffraction limit. Here, we report the imaging of SPEs in layered hBN with a spatial resolution of 63 nm using ground state depletion (GSD) nanoscopy. Furthermore, we show that SPEs in hBN possess nonlinear photophysical properties which can be used to realize a new variant of GSD that employs a coincident pair of doughnut-shaped lasers to reduce the laser power that is needed to achieve a given resolution target. Our findings expand the current understanding of the photophysics of quantum emitters in layered hBN and demonstrate the potential for advanced nanophotonic and bio-imaging applications which require localization of individual emitters with super-resolution accuracy.

physics.optics↗

arXiv2017

Design of photonic microcavities in hexagonal boron nitride

We propose and design photonic crystal cavities (PCCs) in hexagonal boron nitride (hBN) for diverse photonic and quantum applications. Two dimensional (2D) hBN flakes contain quantum emitters which are ultra-bright and photostable at room temperature. To achieve optimal coupling of these emitters to optical resonators, fabrication of cavities from monolithic hBN is therefore required, to maximize the overlap between cavity optical modes and the emitters. Here, we design 2D and 1D PCCs using anisotropic indices of hBN. The influence of underlying substrates and material absorption are investigated, and spontaneous emission rate enhancements are calculated. Our results are promising for future quantum photonic experiments with hBN.

physics.app-ph↗

arXiv2017

Photophysics of GaN single photon sources in the visible spectral range

In this work, we present a detailed photophysical analysis of recently-discovered optically stable, single photon emitters (SPEs) in Gallium Nitride (GaN). Temperature-resolved photoluminescence measurements reveal that the emission lines at 4 K are three orders of magnitude broader than the transform-limited widths expected from excited state lifetime measurements. The broadening is ascribed to ultra-fast spectral diffusion. Continuing the photophysics study on several emitters at room temperature (RT), a maximum average brightness of ~427 kCounts/s is measured. Furthermore, by determining the decay rates of emitters undergoing three-level optical transitions, radiative and non-radiative lifetimes are calculated at RT. Finally, polarization measurements from 14 emitters are used to determine visibility as well as dipole orientation of defect systems within the GaN crystal. Our results underpin some of the fundamental properties of SPE in GaN both at cryogenic and RT, and define the benchmark for future work in GaN-based single-photon technologies.

quant-ph↗

arXiv2017

Resonant Excitation of Quantum Emitters in Hexagonal Boron Nitride

Quantum emitters in layered hexagonal boron nitride (hBN) have recently attracted a great attention as promising single photon sources. In this work, we demonstrate resonant excitation of a single defect center in hBN, one of the most important prerequisites for employment of optical sources in quantum information application. We observe spectral linewidths of hBN emitter narrower than 1 GHz while the emitter experiences spectral diffusion. Temporal photoluminescence measurements reveals an average spectral diffusion time of around 100 ms. On-resonance photon antibunching measurement is also realized. Our results shed light on the potential use of quantum emitters from hBN in nanophotonics and quantum information.

cond-mat.mtrl-sci↗

arXiv2017

Room-temperature solid state quantum emitters in the telecom range

On demand single photon emitters (SPEs) play a key role across a broad range of quantum technologies, including quantum computation, quantum simulation, quantum metrology and quantum communications. In quantum networks and quantum key distribution protocols, where photons are employed as flying qubits, telecom wavelength operation is preferred due to the reduced fibre loss. However, despite the tremendous efforts to develop various triggered SPE platforms, a robust source of triggered SPEs operating at room temperature and the telecom wavelength is still missing. Here we report a triggered, optically stable, room temperature solid state SPE operating at telecom wavelengths. The emitters exhibit high photon purity (~ 5% multiphoton events) and a record-high brightness of ~ 1.5 MHz. The emission is attributed to localized defects in a gallium nitride (GaN) crystal. The high performance SPEs embedded in a technologically mature semiconductor are promising for on-chip quantum simulators and practical quantum communication technologies.

quant-ph↗