Avalanche Sensing via Kerr frequency comb in an Optical Microcavity

Abstract

Sensors based on optical microcavities enhance light-matter interactions within an ultraconfined volume, enabling high-sensitivity detection across a wide range of sensing applications. In these systems, environmental perturbations modify the intrinsic resonance properties of the cavity, typically manifested as frequency shifts, linewidth broadening, or mode splitting. However, the minimum resolvable change in these spectral properties fundamentally limits the overall sensor sensitivity. Here, we propose a new avalanche sensing scheme enabled by Kerr nonlinearity. Instead of relying on the detection of frequency shifts, our approach exploits abrupt state transitions in a Kerr frequency comb to amplify weak perturbations. We provide a theoretical analysis of the underlying mechanism of this scheme and validate the concept through both coupled-mode theory (CMT) modeling and full-wave electromagnetic simulations.

Figures (4)

• Figure 1: Principle of avalanche-inspired Kerr microcavity sensing. Four-quadrant schematic comparing conventional and avalanche detection paradigms for photon/particle sensing. While traditional sensing detects a particle by resolving the minute perturbation it induces on the cavity resonance frequency, avalanche approach's sensitivity is enhanced by Kerr nonlinearity: the particle-induced shift of the cavity eigenfrequency drives the intracavity Kerr comb soliton across a state-transition boundary, converting an ultrasmall frequency perturbation into a macroscopic comb-state change.
• Figure 2: Numerical simulation of the sensing dynamics governed by the LLE. (a) Spatiotemporal evolution of the intracavity field intensity. (b) Selected spectral (top) and temporal (bottom) snapshots.
• Figure 3: FDTD validation of the avalanche sensing mechanism. (a) Bifurcation diagram of Kerr-comb states, with the operating regime marked by a dashed box. Three sensing scenarios are annotated: (i)–(ii) correspond to proper biasing where the particle-induced shift drives the operating point across the boundary and triggers a comb-state transition, whereas (iii) illustrates a trivial mis-biasing case where the operating point moves but no transition occurs, rendering the particle event unobservable. (b) Electric-field distribution of the pumped mode with a zoomed-in view (right) highlighting the local perturbation from the nanoparticle. (c) Three distinct regimes observed in the simulation: breathing solitons (top) and two soliton regimes (middle and bottom), corresponding to scenarios (i), (ii), and (iii). (d) Intracavity states in these three regimes without (top) and with (bottom) a nanoparticle. (e) Spectral profiles in the (ii) regime: unperturbed (left) and perturbed (right).
• Figure 4: Sensitivity comparison between the traditional frequency shift approach and the proposed method. The blue line shows the limit of frequency shift detection. The pink region indicates the theoretical sensitivity range achievable with avalanche method. The purple open squares represent the projected sensitivities of avalanche detection if using experimental configurations reported in RefsJin2021Li2018Raja2019zhang2023Shen24Xiang2021.