Fig. 1. Schematic of the NV color-center fluorescence excitation before and after treatment of the diamond sample.

Fig. 2. Simulated curves of diamond transmittance for TiO2/SiO2 dielectric films with different periods with central wavelengths of photonic bandgaps at (a) 637 nm and (b) 697 nm.

Fig. 3. Characterization of one-dimensional photonic crystals on sample 2. (a) SEM image of longitudinally formed TiO2 and SiO2 alternating dielectric films. (b) XRD patterns of TiO2 dielectric films on the diamond surface. (c) XRD patterns of SiO2 dielectric films on the diamond surface.

Fig. 4. Optical properties of diamond samples before and after deposition of periodic dielectric films. (a) Transmittance of samples 1 and 2. (b) Photoluminescence (PL) spectrum of sample 1 with and without 1D photonic crystal. (c) PL spectrum of sample 2 with and without 1D photonic crystal.

Fig. 5. Spectral analysis of diamond NV color centers before and after treatment. (a) Integrated area of ZPL and phonon sidebands (573–578 nm) for NV0 color centers in sample 2. (b) Integrated area of ZPL and phonon sidebands (636–640 nm) for NV− color centers in sample 2. (c) Population distribution of NV0 color centers with and without 1D photonic crystal. (d) Population distribution of NV− color centers with and without 1D photonic crystal.

Fig. 6. Quantum coherence and absorption properties of diamond sample 2. (a) ODMR spectra fitted with Lorentzian lines before and after treatment. (b) Nonuniform spin relaxation time before and after treatment. (c) Absorption spectrum of the diamond sample in the UV-VIS band; inset shows transmission properties.

Fig. 7. Schematic depicting the excitation of excess electrons in impurity nitrogen near negatively charged nitrogen-valance color centers in diamonds. The inset illustrates the variation in NV center energy levels, with black lines representing energy levels without photonic crystals and red lines representing energy levels with photonic crystals.

Fig. 8. (a) Zero magnetic-field ODMR spectra of sample 3, measured at different laser powers. (b) Laser power dependence of the fluorescence intensity and FWHM of the ODMR spectra.