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: UTS OPUS or 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.
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: UTS OPUS or 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.
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: UTS OPUS or 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.
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: UTS OPUS or 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.
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: UTS OPUS or 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.
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: UTS OPUS or 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.