Effect of Nanopillar Sidewall Angle on Photon Collection Efficiency in Diamond Emitters

Nitrogen-vacancy (NV) centers in diamond are valuable for quantum computing, sensing, and secure communication due to their stable room-temperature operation. However, efficient photon collection is limited by diamond’s high refractive index, leading to significant internal reflection. This work investigates how varying the sidewall angle of diamond nanopillars can affect photon collection efficiency, using finite element method (FEM) simulations. Results indicate that nanopillars with sidewall angles near 90 degrees optimize collection for x-oriented dipoles, while y-oriented dipoles perform best around 86 degrees. NV center depth within the nanopillar also affects efficiency, with certain depths favoring specific angles. Our findings show that angled sidewalls can enhance photon collection while also provide greater structural stability compared to vertical designs, offering a practical pathway to improve NV center-based quantum devices.