Reconfigurable high-order exceptional points in coupled optical parametric oscillators for enhanced sensing

Non-Hermitian systems around exceptional points (EPs) demonstrate increased sensitivity as the EP order increases. We propose a protocol for constructing a reconfigurable non-Hermitian system consisting of three coupled optical parametric oscillators (OPOs) and demonstrate its enhanced sensitivity around EPs. The coupled OPO system exhibits reconfigurable high-order EPs and corresponding-order enhanced sensitivity (i.e. fourth and sixth order) when it is subjected to pump modulation. Furthermore, the coupled OPO system can synthesize directly a Floquet non-Hermitian system by introducing periodic pump modulation, and can achieve a tunable second-order Floquet EP without periodic modulation of the coupling rates. The convenient flexibility of the coupled OPO system allows it to operate at EPs of different orders and customize a Floquet EP by manipulating the pump parameters. Our protocol can thus contribute to the development of high-performance sensors and precision measurement devices by exploring the unique features of non-Hermitian systems around various EPs.