Study on the Enhancement of Diamond Fluorescence Characteristics by Multi-layer Anti-reflection Coating

Quantum sensing has become a rapidly growing research within the area of sensor, which can break through the limits of traditional physical sensing and make sensing accuracy to the nanometer scale. Meanwhile nitrogen-vacancy (NV) center in bulk diamond as a sensor has varieties of applications because of its excellent characteristics. However, there are large optical reflection and low fluorescence collection efficiency at the diamond-air interface because of the large refractive index gap between diamond and air, thereby reducing the sensing sensitivity. In this work, we report a multi-layer anti-reflection coating and fabrication on the surface of diamond with genetic algorithm to solve optimization value of the average reflectance $R_{ave}$ in the wavelength range of 600–800 nm. And we fabricate SiO2-Si3N4 double-layer anti-reflection coating on diamond substrate by plasma chemical vapor deposition. Experiment results show that with an anti-reflection coating, the fluorescence collection efficiency is significantly improved, and the average transmittance in the wavelength range of 600–800 nm is increased from 82.8% to 96.7%.