Voltage-induced modulation in the charge state of Si-vacancy defects in diamond using high voltage nanosecond pulses

Silicon-vacancy defects have been identified as a promising optical transition for quantum communications, quantum control, and quantum information processing. In the work presented here, we demonstrate a voltage-controlled mechanism by which the photoluminescent (PL) emission from silicon-vacancy (Si-V) defects in diamond can be modulated. In particular, we can selectively produce emission from the negatively charged state of this defect (i.e., Si-V ), which exhibits narrow (C1⁄4 4 nm) emission at 738 nm at low laser power. This approach uses high voltage (2–5 kV) nanosecond pulses applied across top and bottom electrodes on a 0.5mm thick diamond substrate. In the absence of high voltage pulses, we observe no emission at 738 nm. This feature increases monotonically with peak pulse voltage, pulse repetition rate (i.e., frequency), and incident laser intensity. We observe saturation of the PL intensity for pulse voltages above 3.2 kV and frequency above 100Hz. Based on electrostatic simulations, we estimated the local electric field intensity near the tip of the Cu electrode to be 2.8 106 V/cm at these voltages. However, as a function of laser power, we observe a linear dependence of PL intensity without saturation. These saturating and non-saturating behaviors provide important insight into the voltage-induced charging mechanisms and kinetics associated with this process. Published under an exclusive license by AIP Publishing. https://doi.org/10.1063/5.0066537 Single photon emission from nitrogen-vacancy (NV) centers in diamond has been studied extensively over the past 20 years, as a promising system for realizing secure quantum communication and quantum sensing applications. More recently, the silicon-vacancy feature in the luminescence of diamond has been found to be particularly sensitive to the charge state of this defect. In particular, the negatively charged Si-V emits at 738 nm, whereas the charge neutral (Si-V) emits at 946 nm. Unlike NV emission, which is quite broad ( 200nm) at room temperature due to a wide array of phonon sidebands, the Si-V feature is spectrally narrow. These spectrally narrow photons have a high degree of indistinguishability and are better able to couple to photonic crystal cavities and waveguides making them promising candidates for solid-state-based quantum technologies. Thanks to recent advancements in chemical vapor deposition (CVD) growth techniques, it is now possible to produce isolated Si-V defects in nano-diamond. This has led to a reinvigoration of the field thanks to a significant improvement in photon count rates and optical properties of such samples. To date, single photon emission has been observed from Si-V defects in type IIa CVD diamond, nano-diamonds, and diamond nanowires with g values of 0.266 0.05, 0.1, and <0.5, respectively. The higher quality samples have also enabled for a deeper understanding of the electronic structure of the Si-V center. The Si-V defect provides a unique molecular structure with the interstitial silicon atom being placed between two unoccupied carbon sites. This results in an inversion symmetry (D3d) of the splitvacancy configuration, which is subsequently responsible for the high spectral stability as it protects the optical transition from local electric field fluctuations. Studies of the electronic structure of the defect have revealed an S1⁄4 1 ground state for the neutral Si-V and an S1⁄4 1/2 ground state for the negative configuration, where the Appl. Phys. Lett. 119, 171101 (2021); doi: 10.1063/5.0066537 119, 171101-1 Published under an exclusive license by AIP Publishing Applied Physics Letters ARTICLE scitation.org/journal/apl