We demonstrate optical spin polarization of the neutrally-charged silicon-vacancy defect in diamond (SiV 0 ), an S = 1 defect which emits with a zero-phonon line at 946 nm. The spin polarization is found to be most efficient under resonant excitation, but non-zero at below-resonant energies. We measure an ensemble spin coherence time T2>100 µs at low-temperature, and a spin relaxation limit of T1 > 25 s. Optical spin state initialization around 946 nm allows independent initialization of SiV 0 and NV − within the same optically-addressed volume, and SiV 0 emits within the telecoms downconversion band to 1550 nm: when combined with its high Debye-Waller factor, our initial results suggest that SiV 0 is a promising candidate for a long-range quantum communication technology.Point defects in diamond have attracted considerable interest owing to their application for quantum information processing, communication, and metrology. The most-studied defect, the negatively-charged nitrogenvacancy (NV − ) center, possesses efficient optical spin polarization and spin-state dependent fluorescence, enabling its exploitation as an ultra-sensitive nano-scale magnetic field sensor [1][2][3]. However, the zero phonon line (ZPL) of NV − accounts for only a few percent of its total emission [4], leading to low efficiency in coherent photonic applications. The negatively-charged siliconvacancy (SiV − ) center has also received significant interest as its high Debye-Waller factor (≈ 0.8 [5]) makes it an attractive candidate for long-range quantum computation and communication. However, the exceptional optical properties of SiV − are not matched by its spin properties, where a large spin-orbit coupling in the ground state enables phonon-assisted spin-state depopulation, resulting in spin-lattice relaxation-limited coherence lifetimes of 40 ns even at 5 K [6]: efforts are ongoing to overcome this limitation by strain engineering, but currently liquid helium temperatures and below are required to access and readout SiV − spin states [7].The neutrally-charged silicon-vacancy (SiV 0 ) has a ground state electron spin S = 1. Unlike the NV center, where the nitrogen remains covalently bonded to three carbon atoms and the nitrogen-vacancy axis forms a C 3v symmetry axis, the silicon atom in SiV adopts a bond-center location, with a D 3d axis formed by the 1 1 1 joining the split-vacancy [ Fig. 1(a)]. SiV 0 has been characterized both by electron paramagnetic resonance (EPR) [8,9] and optical absorption/photoluminescence (PL) [10]. Similarly to SiV − , the neutral charge state also has a high Debye-Waller factor, with the majority of its photons emitted at the primary zero-phonon line (ZPL) at 946 nm (1.31 eV) [ Fig. 1(b)]: this transition has been shown to occur between a 3 A 2g ground state (GS) We have studied SiV 0 in two samples grown by chemical vapor deposition (CVD); silicon was introduced by adding silane to the process gasses during growth. Sample A was grown on a {1 0 0}-oriented high pressure high temperature (HPHT) substrate, ir...
In this paper, we analyse the prospects for using nitrogen-vacancy centre (NV) containing diamond as a laser gain material by measuring its key laser related parameters. Synthetic chemical vapour deposition grown diamond samples with an NV concentration of ~1 ppm have been selected because of their relatively high NV concentration and low background absorption in comparison to other samples available to us. For the samples measured, the luminescence lifetimes of the NV- and NV0 centres were measured to be 8±1 ns and 20±1 ns respectively. The respective peak stimulated emission cross-sections were (3.6±0.1)×10-17 cm2 and (1.7±0.1)×10-17 cm2. These measurements were combined with absorption measurements to calculate the gain spectra for NV- and NV0 for differing inversion levels. Such calculations indicate that gains approaching those required for laser operation may be possible with one of the samples tested and for the NV- centre
Organometallic complexes with novel activation mechanisms are attractive anticancer drug candidates.
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