Laser Direct Writing of Visible Spin Defects in Hexagonal Boron Nitride for Applications in Spin-Based Technologies

Optically addressable spins in two-dimensional hexagonal boron nitride (hBN) attract widespread attention for their potential advantages in on-chip quantum devices, such as quantum sensors and quantum networks. A variety of spin defects have been found in hBN, but no convenient and deterministic generation methods have been reported for other defects except the negatively charged boron vacancy (VB). Here we report that by using femtosecond laser direct writing technology, we can deterministically create spin defect ensembles with spectral range from 550 to 800 nm on nanoscale hBN flakes. Positive single-peak optically detected magnetic resonance (ODMR) signals are detected in the presence of a magnetic field perpendicular to the substrate, and the contrast can reach 0.8%. With the appropriate thickness of hBN flakes, substrate, and femtosecond laser pulse energy, we can deterministically and efficiently generate a bright spin defect array. Our results provide a convenient deterministic method to create spin defects in hBN, which will motivate more endeavors for future research and applications of spin-based technologies such as a quantum magnetometer array.