Enhanced Optical Microcavity Sensing Via Extended Polarization Interferometry With Postselection

ABSTRACT High‐sensitivity optical microcavity sensing faces the challenge of limited dynamic range for detecting time‐varying signals. To address the challenge, an enhanced optical microcavity sensing approach is proposed by integrating an extended polarization interferometer with postselection. The approach exploits both transmission and phase characteristics of the microcavity simultaneously. By adjusting coupling strength and postselection angle, the approach creates distinct phase response regions, thereby achieving significantly improved response compared to the standard transmission method. The dynamic range extends from at most twice the full width at half maximum to the free spectral range. The gain factor depends on material properties, cavity size, resonant wavelength, and quality factor, potentially reaching three to four orders of magnitude for cavities with a quality factor of 10 8 . Furthermore, the approach is compatible with quantum resources, enabling the potential for precision beyond the standard quantum limit. By exploiting the differences between dual‐polarized cavity modes, the feasibility is verified by combining the approach with a polarization Sagnac interferometer. Experimental results demonstrate over 34.24 dB improvement in detection sensitivity, and an additional 12.29 dB enhancement is achieved using coherent states and heterodyne detection. The approach offers a promising solution for optical microcavity sensing across various scenarios.