Anti-PT symmetric resonant sensors for nonreciprocal frequency shift demodulation

Harnessing anti-parity-time (anti-PT) symmetry and the resonant sensing scheme based on white-light multi-beam interferometry, this Letter displays high-sensitivity demodulation of nonreciprocal frequency shifts (Δ). A comprehensive analysis of dissipative coupling (<i>κ</i>) in the anti-PT symmetric resonant fiber-optic sensors is conducted, with particular emphasis on studying the peak splitting phenomenon in the output power spectrum within the Δ - <i>κ</i> space. Based on the observed power spectrum splitting characteristics, two distinct operational modes, the zero-bias state and biased state configurations, are proposed. Simulations reveal that introduction of dissipative coupling can significantly enhance the sensitivity of the proposed sensors compared to traditional Hermitian sensors, achieving a remarkable 10-fold sensitivity improvement when <i>κ</i> = 0.995<i>γ</i>. Specific fiber-optic sensing systems tailored for the Sagnac effect and Faraday effect are also demonstrated for practical sensor design and implementation.