In this presentation, we delve into hBN’s potential as a host for photon emitters. In our recent publication, we introduced a method for creating defects in hBN with tailored spectral properties and spatial distributions using ion beam irradiation. We demonstrate that gallium ions efficiently produce emitters, with Raman spectroscopy identifying defect vibrational signatures. Spectral tuning over 200 nm is achieved through thermal annealing, regardless of ion species, energy, or density. This process is confirmed by Raman spectroscopy, indicating changes in defects' configurations. Coupling a focused ion beam system with annealing, we achieve precise control over emitters' spectral and spatial properties, advancing quantum technologies by enabling customization of emitter properties in hBN.
This contribution discusses the role of hexagonal Boron Nitride (hBN) as a host for photon emitters. In this study we employ gallium ion implantation to create emitters within hBN. Gallium ions are found to be optimal for generating many emitters, when both the ion energy and fluence are carefully controlled. Post-irradiation thermal annealing induces defect transmutation, providing spectral tunability to the emitters. Together with Focused Ion Beam (FIB) implantation, allowing for nanoscale defect positioning, it is possible to precisely pattern multiple photon emitters at various optical frequencies on one platform. Overall, the research highlights hBN potential in advancing quantum technologies.
Quantum emitters in hexagonal boron nitride (hBN) crystals are optimal candidates for the observation of single photon emission, but achieving control over their features is a challenging task. In this work, we present the deterministic generation of emitters with selected position and spectral features with a method that combines ion implantation and annealing of the sample. With this method, we even achieved control over the density of emitters. Such control is a fundamental step towards the engineering of emitter ensembles that can be readily embedded in Van der Waals heterostructures and advanced quantum systems.
We study shallow and deep levels in carbon-doped hexagonal boron nitride crystals precipitated from a molten metal solution in a high-temperature furnace. Reflectance and photoluminescence under deep ultraviolet excitation are complemented by spatially resolved experiments by means of a scanning confocal micro-photoluminescence setup operating in the ultraviolet. Isotopically controlled carbon doping does not induce any energy shift of the well-known deep-level emission at 4.1 eV. Our detailed characterization in a series of carbon-doped crystals reveals that the incorporation of carbon during the growth process results in a distinct class of shallow and deep levels in hexagonal boron nitride, calling into question the exact role of carbon in the growth of hexagonal boron nitride and its direct or indirect influence on the formation of the crystal defects.
Metasurfaces control light propagation at the nanoscale for applications in both free-space and surface-confined geometries. However, all recent designs have exhibited concepts using geometrically fixed structures, or used materials with excessive propagation losses, thereby limiting potential applications. Here we show how to overcome these limitations using a reconfigurable hyperbolic metasurface comprising a heterostructure of isotopically enriched hexagonal boron nitride (hBN) in direct contact with a phase-change material (PCM), single crystal vanadium dioxide (VO2). Metallic and dielectric domains in VO2 provide spatially localized changes in the local dielectric environment to tune the wavelength of hyperbolic phonon polaritons (HPhPs) supported in hBN by a factor of 1.6. This contrasts with earlier work using surface phonon polaritons, where propagation could only be observed above a low-loss dielectric phase. We demonstrate the first realization of in-plane HPhP refraction, which obeys Snell’s law and the means for launching, reflecting and transmitting HPhPs at the PCM domain boundaries. To demonstrate practical applications of this platform, we show how hBN could be combined with either VO2 or GeSbTe glasses to make refractive nanophotonic waveguides and lenses. This approach offers control of in-plane HPhP propagation at the nanoscale and exemplifies a reconfigurable framework combining hyperbolic media and PCMs to design new optical functionalities including resonant cavities, beam steering and waveguiding.
Conventional optical components are limited to size-scales much larger than the wavelength of light, as changes to the amplitude, phase and polarization of the electromagnetic fields are accrued gradually along an optical path. However, advances in nanophotonics have produced ultrathin, so-called “flat” optical components that beget abrupt changes in these properties over distances significantly shorter than the free space wavelength. While high optical losses still plague many approaches, phonon polariton materials have demonstrated long lifetimes for localized modes in comparison to plasmon-polariton based nanophotonics. Our work predicts a further 14-fold increase in the optic phonon lifetime and we experimentally report a ~3-fold improvement through isotopic enrichment of hexagonal boron nitride (hBN). We establish commensurate increases in the phonon polariton propagation length via direct imaging of polaritonic standing waves by means of infrared nano-optics. Our results provide the foundation for a materials-growth-directed approach towards realizing the loss control necessary for the development of phonon polariton based nanophotonic devices.
We report on the Raman analysis of the phonon lifetimes and decay channels of the A1(LO) and E2(high) phonons of single-crystalline bulk AlN grown using the sublimation- recondensation method. The temperature dependence of the phonon lifetimes was investigated from 10 K to 1275 K. Lifetimes of the A1(LO) phonon and the E2(high) phonon of 0.75 ps and 2.9 ps, respectively, were measured at 10 K. Our experimental results show that the A1(LO) phonons of AlN decay primarily into two phonons of equal energy (Klemens' decay channel), most likely longitudinal- acoustic phonons. AlN is therefore in great contrast to GaN, where a symmetric decay of the A1(LO) phonon is not possible due to a large energy gap between the acoustic and optical phonon branches. For the E2(high) phonon, we find an asymmetric phonon decay. Contributions from two- and three-phonon decay channels were used for the modeling of the temperature dependence of the E2(high) phonon lifetime. Phonon lifetimes and decay channels of the E1(LO), A1(TO) and E1(TO) phonons of AlN were also investigated.
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