Exceptional points (EPs) — spectral singularities of non-Hermitian linear systems — have recently attracted interest for sensing. While initial proposals and experiments focused on enhanced sensitivities neglecting noise, subsequent studies revealed issues with EP sensors in noisy environments. Here we propose a single-mode Kerr-nonlinear resonator for exceptional sensing in noisy environments. Based on the resonator’s dynamic hysteresis, we define a signal that displays a square-root singularity reminiscent of an EP. However, our sensor has crucial fundamental and practical advantages over EP sensors: the signal-to-noise ratio increases with the measurement speed, the square-root singularity is easily detected through intensity measurements, and both sensing precision and information content of the signal are enhanced around the singularity. Our sensor also overcomes the fundamental trade-off between precision and averaging time characterizing all linear sensors. All these unconventional features open up new opportunities for fast and precise sensing using hysteretic resonators.

NWO VENI , European Research Council (ERC)
Interacting Photons

Peters, K., & Rodriguez, S. (2022). Exceptional precision of a nonlinear optical sensor at a square-root singularity. Phys.Rev.Lett., 129(1), 013901: 1–7. doi:10.1103/PhysRevLett.129.013901