An experiment has been proposed for laser polarization signal measurement, with the rotation angle and ellipticity being measured simultaneously. The proposed experiment is immune to signal-to-noise ratio degradation due to the finite extinction ratio of polarizing elements used to construct the composite polarization measurement setup. Noise analysis is carried out to show that the proposed scheme allows one to reach the quantum noise limit in the simultaneous measurement of the polarization angle and ellipticity. This work should be of great interest for experiments such as observation of vacuum magnetic birefringence, spin-orbital interaction, material characterization, polarization microscopy, or biomedical optics.
An experiment has been proposed for laser polarization signal measurement, with the rotation angle and ellipticity being measured simultaneously. The proposed experiment is immune to signal-to-noise ratio degradation due to the finite extinction ratio of polarizing elements used to construct the composite polarization measurement setup. Noise analysis is carried out to show that the proposed scheme allows one to reach the quantum noise limit in the simultaneous measurement of the polarization angle and ellipticity. This work should be of great interest for experiments such as observation of vacuum magnetic birefringence, spin-orbital interaction, material characterization, polarization microscopy, or biomedical optics.
An experimental scheme is proposed for squeezing-enhanced simultaneous measurement of the polarization angle and ellipticity of laser beam beyond the shot noise limit. In the scheme, a two-mode squeezed light is exploited to enhance the sensitivity of the measurement of polarization rotation angle, and a single-mode squeezed light is used to improve the sensitivity of ellipticity measurement. Noise analysis is performed to show that the signal-to-noise ratios in both the measurements of polarization angle and ellipticity can exceed the shot noise limit. This work is expected to be of considerable interest for experiments such as the observation of vacuum magnetic birefringence, gravitational wave detection, spin–orbital interaction, material characterization, polarization microscopy, atomic magnetometer, or biomedical optics.
Magneto-optical (MO) effects, manifested as a complex rotation of light polarization under an external magnetic field, are widely utilized in optical isolators, sensors, data storage, and magnetic imaging. Accurate measurement of both the rotation angle (the real part) and the ellipticity (the imaginary part) is essential for fundamental research and device applications. However, existing measurement schemes generally cannot determine these two quantities simultaneously within a single experimental process. In this work, we propose a scheme based on weak measurement using two pointers, enabling the simultaneous measurement of the rotation angle and ellipticity within a single meter state. This method was experimentally implemented to measure the magneto-optical Kerr effect under various configurations—longitudinal, polar, and transverse. Moreover, the proposed approach is also applicable to the measurement of the Faraday effect and magnetic linear birefringence, demonstrating its broad applicability. This work contributes to the advancement of high-precision measurement techniques for MO effects and supports their wider application across multiple fields.
Magneto-optical (MO) effects, manifested as a complex rotation of light polarization under an external magnetic field, have found renewed and advanced applications in integrated photonics, intelligent sensing, ultrafast magnetic recording, and high-resolution magnetic imaging. Accurate measurement of both the rotation angle (the real part) and the ellipticity (the imaginary part) is essential for fundamental research and device applications. However, existing measurement schemes generally require separate measurements or distinct detection configurations and therefore cannot simultaneously retrieve both quantities in a single measurement. In this work, we propose a scheme based on weak measurement using dual-pointers, enabling the simultaneous measurement of the rotation angle and ellipticity within a single meter state. This method was theoretically and experimentally implemented to measure the magneto-optical Kerr effect (MOKE), the Faraday effect, and the Cotton-Mouton effect, demonstrating its broad applicability. This work contributes a characterization technique for the complex angle of MO effects, supporting potential applications across spintronics, quantum materials, and advanced optical sensing.
We have developed a single-beam spin-exchange relaxation-free comagnetometer using elliptically polarized light for dual-axis rotation measurement. The light beam propagating through the glass cell is simultaneously used for optical pumping and signal extraction. Combined with transverse magnetic field modulation, the rotation information can be collected through a balanced polarimeter module and a lock-in amplifier. Also, we propose a decoupling method by adjusting the phase shift of the reference signal, allowing the device to realize biaxial signal decoupling while still maintaining its self-compensation state. Compared to those without decoupling, our method improves the performance of our device in its signal-to-noise ratio and rotation sensitivity. The single-beam comagnetometer scheme and the decoupling method have a positive impact on the development of miniaturized atomic sensors for high-precision inertial measurement.
The signal to noise ratio in atomic magnetometry is fundamentally limited by the optical depth of the atomic ensemble. During the last decade, different technics for optical depth enhancement has been developed by several groups, some of them involving the implementation of an optical cavity. This thesis evaluates the performance of such an implementation by the polarization read out noise analysis of an optical cavity with similar characteristics as the already implemented by other groups. We obtained an estimated value for the signal to noise ratio enhancement with a cavity of 814 Finesse, and we studied the behaviour of the different sources of polarization noise in this system.
The development of new techniques to improve measurements is crucial for all sciences. By employing quantum systems as sensors to probe some physical property of interest allows the application of quantum resources, such as coherent superpositions and quantum correlations, to increase measurement precision. Here we experimentally investigate a scheme for quantum target detection based on linear optical measurement devices, when the object is immersed in unpolarized background light. By comparing the quantum (polarization-entangled photon pairs) and the classical (separable polarization states) strategies, we found that the quantum strategy provides us an improvement over the classical one in our experiment when the signal-to-noise ratio is greater than 1/40, or about 16 dB of noise. This is in constrast to quantum target detection considering nonlinear optical detection schemes, which have shown resilience to extreme amounts of noise. A theoretical model is developed which shows that, in this linear-optics context, the quantum strategy suffers from the contribution of multiple background photons. This effect does not appear in our classical scheme. By improving the two-photon detection electronics, it should be possible to achieve a polarization-based quantum advantage for a signal-to-noise ratio that is close to 1/400 for current technology.