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We proposed a method to effectively fabricate negatively charged nitrogen vacancy (NV − ) centers close to the diamond surface by applying femtosecond laser writing technique. With a thick layer of silicon (Si) nanoballs coated, diamond surface was irradiated by high-fluence femtosecond laser pulses. A large number of NV − centers were created around the laser ablation crater area without thermal annealing. The distribution of the NV − centers was expanded to about 50 μm away from the crater center. To demonstrate the function of Si nanoballs, we performed the exactly same laser illumination process on the bare region of the sample surface. In this case, only a few NV − centers were generated around ablation crater. At distance of 32 μm away from crater centers, the NV − density for the case with nanoballs was up to 15.5 times higher compared to the case without nanoballs. Furthermore, we also investigated the influence of laser fluence and pulse number on the NV − density for the case with Si-nanoball layer. Finally, the formation mechanism of NV − centers and the role of Si nanoballs were explained via Coulomb explosion model. The method is demonstrated to be a promising approach to efficiently and rapidly fabricate NV − centers close to the surface of the diamond, which are significant in quantum sensing. Furthermore, the results provide deep insights into complex light-matter interactions.

Point defects in the wide bandgap III-nitride semiconductors are recently reported to be one kind of the most promising near-infrared (NIR) quantum emitters operating at room temperature (RT). But the...

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Single-photon emitters (SPEs) are attractive as integrated platforms for quantum applications in technologically mature wide-bandgap semiconductors since their stable operation at room temperature or even at high temperatures. In this study, we systematically studied the temperature dependence of the SPE in AlGaN micropillars by experiment. The photoluminescence (PL) spectrum, PL intensity, radiative lifetime and second-order autocorrelation function measurements are investigated over the temperature range from 303-373 K. The point defects of AlGaN show strong zero phonon line (ZPL) in the wavelength range of 800-900 nm and highly antibunched photon emission even up to 373 K. Our study reveals a possible mechanism for linewidth broadening in AlGaN SPE at high temperatures. This indicates a possible key for on-chip integration applications based on this material operating at high temperatures.

The single-scattering-foil method is the basic of passive proton beam spreading system. In this paper, the angular distribution and energy distribution of proton beam on passing through a single scattering foil are calculated using Monte-Carlo multi-particle transport code Fluka2006.3b.2., including the effect of proton energy, scattering material and target thickness on scattering angle. The result shows that thin-high-atomic-number material can be used as the scattering material.