Focusing grating coupler for the generation of quantum sensors

We report the development and experimental testing of focusing grating couplers (FGCs) designed for integration with surface ion traps, aiming to advance compact ion-based technologies for next-generation quantum sensors to be used in ion frequency standards, gravimetry, and quantum computing. Through analytical calculations, we optimized the simulation and fabrication processes. Using numerical simulations, we further optimized the focusing configuration of the grating couplers to achieve a focal point approximately 210 µm above the chip surface. The fabricated focusing couplers were experimentally tested and confirmed to effectively focus laser radiation at a height of 200-210 µm above the chip surface.