Fig. 1: Enhanced sensing using quadratic cavity simultons.

a Schematic depiction of sensing in the simulton regime of a synchronously-pumped optical parametric oscillator at degeneracy. The bright soliton in the signal interacts with the sample every round trip, and the resulting competing nonlinear dynamics generate the measured signal response. b Specifically, stable simulton operation requires the simulton group advance, ΔT, to balance the round-trip group delay, ΔT_RT, and the parametric gain to balance the sample loss, α_samp, and output coupling. c Schematic representation of linear absorption sensing governed by the Beer-Lambert Law for light interacting with a sample over a path length L. d Linear methods (light blue region) face limitations in the achievable sensitivity at high sample concentrations. In contrast, active cavity sensing with quadratic cavity (orange) can achieve high sensitivities at high sample concentrations. T_rep, pump repetition period; T_circ, pulse circulation time in the cavity; ΔT, simulton group advance; T_RT, cold cavity round-trip time ΔT_RT, round-trip group delay; χ⁽²⁾, second-order susceptibility; ω, angular frequency; α_samp, sample absorption coefficient; OC, output coupling; P_in, input power; P_out, output power; L, path length; ℏ, reduced Planck’s constant.