Sensor-performance limitations at exceptional points

Determine the performance limitations of sensors operating at exceptional points in non-Hermitian photonic systems.

Background

Exceptional points (EPs) are non-Hermitian spectral degeneracies where eigenfrequencies and eigenmodes coalesce. EPs have been proposed for ultra-sensitive sensing applications, motivating careful quantification of feasible performance in realistic systems.

The paper develops a contour-integration and algorithmic-differentiation framework to compute eigenfrequency sensitivities near EPs, enabling analysis and optimization of EP-based devices. Within this context, the authors explicitly note that limitations affecting sensor performance at EPs remain an open problem in the field.