Kim, S, Duong, NMH, Nguyen, M, Lu, TJ, Kianinia, M, Mendelson, N, Solntsev, A, Bradac, C, Englund, DR & Aharonovich, I 2019, 'Integrated on Chip Platform with Quantum Emitters in Layered Materials', Advanced Optical Materials, vol. 7, no. 23.View/Download from: Publisher's site
© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Integrated quantum photonic circuitry is an emerging topic that requires efficient coupling of quantum light sources to waveguides and optical resonators. So far, great effort is devoted to engineering on-chip systems from 3D crystals such as diamond or gallium arsenide. In this study, room-temperature coupling is demonstrated of quantum emitters embedded in layered hexagonal boron nitride to an on-chip aluminum nitride waveguide. 1.35% light coupling efficiency is achieved in the device and transmission of single photons through the waveguide is demonstrated. The results serve as foundation for integrating layered materials to on-chip components and realizing integrated quantum photonic circuitry.
Nguyen, M, Zhu, T, Kianinia, M, Massabuau, F, Aharonovich, I, Toth, M, Oliver, R & Bradac, C 2019, 'Effects of microstructure and growth conditions on quantum emitters in gallium nitride', APL Materials, vol. 7, no. 8.View/Download from: Publisher's site
© 2019 Author(s). 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 - characterized 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.
Dietrich, A, Bürk, M, Steiger, ES, Antoniuk, L, Tran, TT, Nguyen, M, Aharonovich, I, Jelezko, F & Kubanek, A 2019, 'Reply to "comment on 'Observation of Fourier transform limited lines in hexagonal boron nitride'"', Physical Review B, vol. 100, no. 4.View/Download from: Publisher's site
© 2019 American Physical Society. In this Reply, we answer to the comments by Langbein [Phys. Rev. B 100, 047401 (2019)10.1103/PhysRevB.100.047401]. We disagree with the argument that our measured spectral shapes and the extracted linewidths are caused by temporal blinking. We give detailed information on our evaluation process to exclude blinking events. Beyond the question raised in the Comment, we analyze the influence of spectral diffusion. Although spectral diffusion is an ongoing limitation for defect centers in hexagonal boron nitride, we prove that it is not influencing our extracted linewidths.
Duong, NMH, Glushkov, E, Chernev, A, Navikas, V, Comtet, J, Nguyen, MAP, Toth, M, Radenovic, A, Tran, TT & Aharonovich, I 2019, 'Facile Production of Hexagonal Boron Nitride Nanoparticles by Cryogenic Exfoliation.', Nano letters, vol. 19, no. 8, pp. 5417-5422.View/Download from: Publisher's site
Fluorescent nanoparticles with optically robust luminescence are imperative to applications in imaging and labeling. Here we demonstrate that hexagonal boron nitride (hBN) nanoparticles can be reliably produced using a scalable cryogenic exfoliation technique with sizes below 10 nm. The particles exhibit bright fluorescence generated by color centers that act as atomic-size quantum emitters. We analyze their optical properties, including emission wavelength, photon-statistics, and photodynamics, and show that they are suitable for far-field super-resolution fluorescence nanoscopy. Our results provide a foundation for exploration of hBN nanoparticles as candidates for bioimaging, labeling, as well as biomarkers that are suitable for quantum sensing.
Gan, W, Tserkezis, C, Cai, Q, Falin, A, Mateti, S, Minh, N, Aharonovich, I, Watanabe, K, Taniguchi, T, Huang, F, Song, L, Kong, L, Chen, Y & Li, LH 2019, 'Atomically Thin Boron Nitride as an Ideal Spacer for Metal-Enhanced Fluorescence', ACS NANO, vol. 13, no. 10, pp. 12184-12191.View/Download from: Publisher's site
Kianinia, M, Bradac, C, Sontheimer, B, Wang, F, Tran, TT, Nguyen, M, Kim, S, Xu, Z-Q, Jin, D, Schell, AW, Lobo, CJ, Aharonovich, I & Toth, M 2018, 'All-optical control and super-resolution imaging of quantum emitters in layered materials.', Nature communications, vol. 9, no. 1, pp. 874-874.View/Download from: Publisher's site
Layered van der Waals materials are emerging as compelling two-dimensional platforms for nanophotonics, polaritonics, valleytronics and spintronics, and have the potential to transform applications in sensing, imaging and quantum information processing. Among these, hexagonal boron nitride (hBN) is known to host ultra-bright, room-temperature quantum emitters, whose nature is yet to be fully understood. Here we present a set of measurements that give unique insight into the photophysical properties and level structure of hBN quantum emitters. Specifically, we report the existence of a class of hBN quantum emitters with a fast-decaying intermediate and a long-lived metastable state accessible from the first excited electronic state. Furthermore, by means of a two-laser repumping scheme, we show an enhanced photoluminescence and emission intensity, which can be utilized to realize a new modality of far-field super-resolution imaging. Our findings expand current understanding of quantum emitters in hBN and show new potential ways of harnessing their nonlinear optical properties in sub-diffraction nanoscopy.
Ngoc My Duong, H, Nguyen, MAP, Kianinia, M, Ohshima, T, Abe, H, Watanabe, K, Taniguchi, T, Edgar, JH, Aharonovich, I & Toth, M 2018, 'Effects of High-Energy Electron Irradiation on Quantum Emitters in Hexagonal Boron Nitride.', ACS Applied Materials and Interfaces, vol. 10, no. 29, pp. 24886-24891.View/Download from: Publisher's site
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.
Nguyen, M, Kim, S, Tran, TT, Xu, Z-Q, Kianinia, M, Toth, M & Aharonovich, I 2018, 'Nanoassembly of quantum emitters in hexagonal boron nitride and gold nanospheres.', Nanoscale, vol. 10, no. 5, pp. 2267-2274.View/Download from: Publisher's site
The assembly of quantum nanophotonic systems with plasmonic resonators is important for fundamental studies of single photon sources as well as for on-chip information processing. In this work, we demonstrate the controllable nanoassembly of gold nanospheres with ultra-bright narrow-band 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 to the quantum emitters and observe the resulting emission enhancement and fluorescence lifetime reduction. The extreme emitter photostability permits analysis at high excitation powers, and delineation of absorption and emission enhancement caused by the plasmonic resonators. 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 × 106 counts per s. Our results are promising for the future employment of quantum emitters in hBN for integrated nanophotonic devices and plasmonic based nanosensors.
Tran, TT, Kianinia, M, Nguyen, M, Kim, S, Xu, ZQ, Kubanek, A, Toth, M & Aharonovich, I 2018, 'Resonant Excitation of Quantum Emitters in Hexagonal Boron Nitride', ACS Photonics, vol. 5, no. 2, pp. 295-300.View/Download from: Publisher's site
© 2017 American Chemical Society. Quantum emitters in layered hexagonal boron nitride (hBN) have recently attracted a great deal of 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 processing applications. We observe spectral line widths of an hBN emitter narrower than 1 GHz while the emitter experiences spectral diffusion. Temporal photoluminescence measurements reveal an average spectral diffusion time of around 100 ms. An 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 processing applications.
Xu, Z-Q, Elbadawi, C, Tran, TT, Kianinia, M, Li, X, Liu, D, Hoffman, TB, Nguyen, M, Kim, S, Edgar, JH, Wu, X, Song, L, Ali, S, Ford, M, Toth, M & Aharonovich, I 2018, 'Single photon emission from plasma treated 2D hexagonal boron nitride.', Nanoscale, vol. 10, no. 17, pp. 7957-7965.View/Download from: Publisher's site
Artificial atomic systems in solids are becoming increasingly important building blocks in quantum information processing and scalable quantum nanophotonic networks. Amongst numerous candidates, 2D hexagonal boron nitride has recently emerged as a promising platform hosting single photon emitters. Here, we report a number of robust plasma and thermal annealing methods for fabrication of emitters in tape-exfoliated hexagonal boron nitride (hBN) crystals. A two-step process comprising Ar plasma etching and subsequent annealing in Ar is highly robust, and yields an eight-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 with emission wavelengths greater than ∼700 nm. Density functional theory modeling suggests that the emitters might be associated with defect complexes that contain oxygen. This is further confirmed by generating the emitters via annealing hBN in air. Our findings advance the present understanding of the structure of quantum emitters in hBN and enhance the nanofabrication toolkit needed to realize integrated quantum nanophotonic circuits.
Dietrich, A, Bürk, M, Steiger, ES, Antoniuk, L, Tran, TT, Nguyen, M, Aharonovich, I, Jelezko, F & Kubanek, A 2018, 'Observation of Fourier transform limited lines in hexagonal boron nitride', Physical Review B, vol. 98, no. 8.View/Download from: Publisher's site
© 2018 American Physical Society. Single defect centers in layered hexagonal boron nitride are promising candidates as single-photon sources for quantum optics and nanophotonics applications. However, spectral instability hinders many applications. Here, we perform resonant excitation measurements and observe Fourier transform limited linewidths down to ≈50 MHz. We investigated the optical properties of more than 600 single-photon emitters (SPEs) in hBN. The SPEs exhibit narrow zero-phonon lines distributed over a spectral range from 580 to 800 nm and with dipolelike emission with a high polarization contrast. Finally, the emitters withstand transfer to a foreign photonic platform, namely, a silver mirror, which makes them compatible with photonic devices such as optical resonators and paves the way to quantum photonics applications.
Kianinia, M, Bradac, C, Sontheimer, B, Wang, F, Tran, TT, Nguyen, M, Kim, S, Xu, Z-Q, Jin, D, Schell, AW, Lobo, C, Aharanovich, I & Toth, M 2019, 'Enhanced Super-Resolution Imaging of Quantum Emitters in Hexagonal Boron Nitride', 2019 Compound Semiconductor Week (CSW), Compound Semiconductor Week, IEEE, Nara, Japan.View/Download from: Publisher's site
Layered van der Waals materials are emerging as compelling two-dimensional platforms for 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 known to host ultra-bright, room-temperature quantum emitters, whose nature is yet to be fully understood. Here, we present a set of measurements which give unique insight into the photophysical properties and level structure of hBN quantum emitters. Specifically, we report the existence of a class of hBN quantum emitters with a fast-decaying intermediate and a long-lived metastable state accessible from the first excited electronic state. Furthermore, by means of a two-laser repumping scheme, we show an enhanced photoluminescence and emission intensity which can be utilized to realize a new modality of far-field super-resolution imaging. Our findings expand current understanding of quantum emitters in hBN and show new potential ways of harnessing their nonlinear optical properties in sub-diffraction nanoscopy.