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Laser & Photonics Review

Enhanced Optical Microcavity Sensing Via Extended Polarization Interferometry With Postselection

Qi Song, Hongjing Li, Ding Wang, C. X. Yu, Xingyu Wu, Jingzheng Huang, Chuan Wang, Guihua Zeng

Published Feb 22, 2026• 2 citations
Publisher

Abstract

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.

DOI
10.1002/lpor.202502072

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physics.opticsCross-listedarXiv:2611.01946•Nov 3, 2026
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.
ABSTRACT Cavity optomechanical (COM) sensors based on whispering‐gallery‐mode (WGM) resonators have emerged as highly sensitive platforms for probing weak external perturbations, enabling diverse applications from precision metrology to fundamental tests of physics. In this work, a quantum‐enhanced scheme for weak‐force sensing in a WGM resonator is proposed. The system leverages phase control between two coherent driving fields and incorporates realistic imperfections to engineer optical squeezing within the cavity. By finely tuning the relative phase, strong optical squeezing and quantum entanglement between counter‐propagating modes are generated within the cavity, achieving an optimal force sensitivity beyond the standard quantum limit (SQL) and a quantum noise reduction of up to three orders of magnitude. Furthermore, optimal parameter regimes for achieving minimal quantum power spectral density are systematically identified. These findings reveal a new route for phase‐enabled quantum sensing in the high‐quality WGM resonator, with potential implications for high‐precision measurements and quantum information technologies.
In this work, the combination of an all-fiber two-mode squeezed state light source and Sagnac interferometer for the experimental realization of a quantum-enhanced strain and curvature sensor is presented here. The former can offer intensity-correlated twin beams, whose intensity difference noise is beyond standard quantum limit. The latter can be prepared by splicing a polarization-maintaining fiber between two standard single-mode fibers. Using the intensity interrogation method tracing the intensity variation of the sensing signal beam, we can obtain the following quantum-enhanced experimental results. In the strain sensing, signal-to-noise ratio (SNR) is enhanced by a maximal factor of 1.54 dB compared with the corresponding classical strategy under balanced measurement condition. Under unbalanced measurement condition, SNR and the sensitivity are enhanced by the maximal factors of 1.39 dB and 0.026 dB/μϵ respectively compared with the corresponding classical counterpart. In the curvature sensing, balanced measurement condition can offer a maximal factor of 1.31 dB SNR enhancement, unbalanced measurement condition will bring the maximal factors of 1.36 dB and 3.31 dB/m−1respectively enhancement in SNR and sensitivity. These results demonstrate the feasibility of the combination of all-fiber non-classical light source and various fiber-based structures as the strain and curvature sensors for many applications that demands sub-poissonian precise measurements.
We analytically show that inserting a driven, two-level system inside a microcavity can improve its optical properties. In this approach, the strong dispersion induced by a pump via population oscillations increases the cavity lifetime experienced by a slightly detuned probe. We further predict that if the cavity is pumped through a resonant channel, optical absorptive or dispersive bistability can be combined with the population-oscillation-induced steep material dispersion to obtain a strong quality-factor enhancement. Moreover, differential amplification coming from the nonlinear feature of the pump transfer function can be used to drastically increase the probe transmission beyond intrinsic characteristics of the resonator. The QQQ-factor enhancement and the differential amplification can be advantageously combined with a frequency pulling effect to stabilize or readjust the microcavity resonance frequency.
Quantum interferometric sensing plays a crucial role in a wide range of applications, including quantum metrology, quantum imaging, and quantum lithography, where minute phase shifts carry valuable physical information. The strength of quantum sensing lies in surpassing classical sensitivity limits, particularly through the use of quantum correlations and squeezing to suppress optical shot noise. Birefringence sensing is crucial for various applications, as it provides detailed information about the material's structure, stress, composition, and environmental conditions. We present an interferometric scheme for detecting unknown small birefringence beyond the shot-noise limit of sensitivity that leverages the hyper-squeezing (squeezed in both number-phase and polarization correlations) within a pair of polarized nonlinear SU(1,1) interferometers, coupled by the birefringence. Specifically, two pairs of crossed-polarization nonlinear media, both generate and measure two-mode quantum light that is squeezed and polarization-entangled. We present a complete theoretical analysis of the interferometer's sensitivity to small birefringence under realistic conditions of gain and internal loss, illuminating the potential for enhancement of the sensitivity by 3-15dB in practical, real-world experiments (the exact achievable enhancement is governed solely by the loss).
Quantum sensing has performance advantages that far exceed classical sensing, where sensing with photons is one of the most useful branches, and fiberization is a significant development approach to achieve a broader range of applications. However, the birefringence effect in optical fibers can cause polarization drift, which severely reduces the sensitivity of measurement on weak signals and influences the development of quantum sensing. In order to solve this problem, we propose a scheme that builds four time-division-multiplexing channels in the system by switching the polarization states of different optical pulses, and achieves the effect of suppressing polarization drift by analyzing and integrating the effective information of the four polarization channels. Moreover, the sensitivity and linear dynamic range of the system can be adjusted by inserting a reference phase. We demonstrate the feasibility of the system via theoretical analysis, and the numerical simulation results show that the scheme can demodulate the signal well and improve the signal-to-noise ratio by 30 dB, even in the case of the signal of the direct demodulation method is drowned out by noise and completely distorted.
Recovering complex optical signals with high sensitivity is central to coherent communication and sensing. Beyond conventional homodyne and heterodyne reception, phase-conjugate twin-wave encoding and phase-sensitive joint detection offer an alternative strategy with enhanced sensitivity. Extending this approach to long-distance transmission of high-order-modulated signals is challenging because optical phase coherence must be maintained at the receiver. Here we experimentally demonstrate injection-locking-assisted phase-conjugated twin-wave reception of 200-MBaud signals with modulation formats up to 256-QAM over 100 km of optical fiber. Optical injection locking regenerates the local oscillator (LO) from a reference transmitted through the 16 dB-loss link, while pilot-assisted optical feedback stabilizes the relative signal-LO phase, enabling coherent combining of the phase-conjugated twin waves at a single balanced photodetector. At equal received signal-photon number per quadrature in each data-carrying optical mode, the measured PCTW signal-to-noise ratio (SNR) exceeds the ideal single-mode homodyne standard quantum limit (SQL) benchmark. The SNR gains over the measured homodyne and conventional heterodyne results are about 3 dB and 6 dB, respectively. Constellation and bit-error-rate measurements show that this gain improves high-order data recovery relative to heterodyne reception. An ideal Gaussian-noise model predicts a photon information efficiency of 1.54 bits per received signal photon for uniform 16-QAM. These results establish an injection-locking-assisted coherent receiver architecture that implements joint detection of phase-conjugated twin waves over 100 km of fiber with enhanced sensitivity, providing a practical route for photon-efficient coherent communication.