Generation and Control of Higher-Order-Mode Lasers in Multimode Silicon Resonators

The generation and control of multidimensional optical fields play a crucial role in advancing applications such as optical communications, sensing, information encoding, and imaging, by maximizing the utilization of optical degrees of freedom and enabling multiple optical channels. Optical lasers are fundamental to these applications as the primary sources of optical fields. However, previous work mainly focused on realizing light sources based on fundamental modes, leaving higher-order modes underutilized. Here, we propose an approach for generating and controlling an on-chip higher-order-mode light source from Raman lasing. We chose the fourth-order mode as an example and generated the fourth-order mode lasing using a compact, high-quality multimode silicon racetrack resonator. The multimode racetrack resonator has a compact footprint of 0.13 mm² using two adiabatic bends and exhibits a high-quality factor of over 1 × 10⁶. The lasing threshold was measured as 0.6 mW. Finally, we show that controlling the higher-order-mode lasing enables mode-switching behavior, which can find potential applications in high-resolution optical systems and quantum optics.