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Non-Hermitian sensors have been widely studied for the enhanced response of their eigenvalues in the proximity of exceptional points. However, it has been shown that noise is enhanced in the same way as sensitivity, thus vanishing the advantages of the exceptional point. Recently, the idea of measuring the frequency splitting of transmission peaks of a non-lasing PT-symmetric sensor has shown the possibility of increasing the signal-to-noise ratio of a sensor close to the so called “transmission peak degeneracy”, with respect to an operating condition away from it. Here we analyze a non-Hermitian optical gyroscope, demonstrating that also anti-PT-symmetric Hamiltonians show an enhanced transmission peaks frequency splitting in the proximity of the transmission peak degeneracy. We also perform an analysis on noise and uncertainties and introduce new figures of merit to compare the proposed anti-PT-symmetric sensor with a classical resonant optical gyroscope. When the uncertainties due to fluctuations of parameters are negligible with respect to the uncertainties due to amplitude noise, the non-Hermitian sensor working at the transmission peak degeneracy is demonstrated to operate better than a classical resonant gyroscope in terms of signal-to-noise ratio.

Resonant label-free biosensors using silicon-on-insulator substrates represent a cutting-edge domain in optical sensing. These devices leverage the high refractive index contrast of silicon-on-insulator materials to create highly sensitive, compact sensors. They are crucial for real-time, precise biomolecular detection in healthcare diagnostics, environmental monitoring, and drug discovery, marking a significant stride in microphotonic technology and its practical applications. Different ring-based resonant configurations have been explored in this context, but a definitive comparative assessment of them was previously lacking in the literature. In our work, we experimentally compare four different ring configurations in terms of figure-of-merit (FoM), showing that the slotted ring performs better than competitive approaches. A silicon photonic chip including tens of ring resonators (RRs) was fabricated and optically characterized considering air and aqueous solutions as cladding. The best sensitivity achieved was 64 nm/RIU for the slotted ring configuration. The ring displayed a Q-factor in the order of $2.57\times 10^{{4}}$ , and the best estimated resolution was in the order of ${10}^{-{4}}~\text {RIU}$ in water. The measured FoM was greater than ${200}~\text {RIU}^{-{1}}$ .