Linguo Xie

Incident-polarization-sensitive and large in-plane-photonic-spin-splitting at the Brewster angle.

In this Letter, we report a phenomenon of large in-plane-photonic-spin-splitting (IPPSS) in the case of a linear polarized Gaussian light beam reflected from an air-glass interface at the Brewster angle. The IPPSS-induced displacement reaches ∼12.4  μm, which is quite larger than the previously reported value. Particularly, the IPPSS is extremely sensitive (∼70  μm/deg) to the incident polarization. We also find that the direction of the spin accumulation can be switched by adjusting the incident polarization slightly. These findings may have useful applications in spin manipulation and precise polarization metrology.

Estimation of optical rotation of chiral molecules with weak measurements.

From its beginning, the measurement of optical rotation (OR) is crucial for the analysis of chiral molecules in many fields. However, the precision measurement of a weak OR signal with conventional setup remains elusive. In this Letter, we experimentally propose a precision method to determine the OR of glucose and fructose based on weak measurements. By using the spin Hall effect of light (SHEL) as a probe, a nonlinear weak measurements model is established that is applicable beyond the Aharonov-Albert-Vaidman (AAV) limit. Due to the high sensitivity of weak measurements amplification with respect to the OR, a tremendous variation of the amplified beam displacement of the SHEL is observed, while the concentration of glucose and fructose is slightly changed.

Precision phase estimation based on weak-value amplification

In this letter, we propose a precision method for phase estimation based on the weak-value amplification (WVA) technique using a monochromatic light source. The anomalous WVA significantly suppresses the technical noise with respect to the intensity difference signal induced by the phase delay when the post-selection procedure comes into play. The phase measured precision of this method is proportional to the weak-value of a polarization operator in the experimental range. Our results compete well with the wide spectrum light phase weak measurements and outperform the standard homodyne phase detection technique.

Precision improvement of surface plasmon resonance sensors based on weak-value amplification

In this paper, a method to improve the precision of prism-coupler-based surface plasmon resonance (SPR) sensors using weak-value amplification (WVA) is presented. A general theory model to describe the post-selected SPR sensing system is established and the polarization-dependent amplitude and phase evolutions induced by the SPR are regarded as the weak interactions in the WVA formalism. As a consequence of WVA, the detected signal can be enhanced with respect to the technical noise which is dependent on the post-selected light intensity. The precision of our method reaches 2.9 × 10-7RIU, which is improved nearly one order of magnitude compared to the conventional sensing technique.

Diffraction-dependent spin splitting in spin Hall effect of light on reflection

We report on a diffraction-dependent spin splitting of the paraxial Gaussian light beams on reflection theoretically and experimentally. In the case of horizontal incident polarization, the spin splitting is proportional to the diffraction length of light beams near the Brewster angle. However, the spin splitting is nearly independent with the diffraction length for the vertical incident polarization. By means of the angular spectrum theory, we find that the diffraction-dependent spin splitting is attributed to the first order expansion term of the reflection coefficients with respect to the transverse wave-vector which is closely related to the diffraction length.

Optimal pre- and post-selections of weak measurements for precision parameter estimation

Weak measurements, which offer a significant signal enhancement with pre- and post-selections, have proven to be powerful for precision metrology. However, the measured precision of the parameter of interest is always limited by the post-selection-induced probe loss, especially in the presence of technical noise. In this paper, we investigate the optimal pre- and post-selections of weak measurements for precision metrology in the presence of technical noise. While weak measurements apply more generally, we experimentally measure the spin splitting induced by the spin Hall effect of light (SHEL) to approach this issue. The highest measured precision of the spin splitting can be obtained with the post-selected state in the nonlinear intermediate regime. Surprisingly, the pre- and post-selections for the largest weak-value amplification are incapable of estimation of the spin splitting, since the amplified shift is independent of the spin splitting. Our results are not restricted to the SHEL and could be app...

Quantitative detection of the respective concentrations of chiral compounds with weak measurements

In this letter, we determine the respective concentrations of glucose and fructose in the mixed chiral solution by simultaneously measuring the optical rotation angle (ORA) and the refractive index change (RIC) with weak measurements. The photonic spin Hall effect (PSHE) serves as a probe in our scheme. The measurement of ORA is based on the high sensitivity of the amplification factor to the polarization state in weak measurements. The measurement of RIC is based on the rapid variation of spin splitting of the PSHE. The measurement precision of the respective concentrations can be achieved to be 0.02 mg/ml. This method can detect traces of enantiomeric impurities and has a potential application in chiral sensing.

The photonic spin Hall effect sensor

In this paper, we present an alternative refractive index sensing scheme based on the photonic spin Hall effect (PSHE). We find that the spin splitting induced by the PSHE shows high sensitivity to the refractive index change (RIC) around the Brewster angle.The refractive index of sample is estimated with a precision of the order of 10−5 refractive index unit (RIU) by measuring the spin splitting with weak measurements. Compared with the surface plasmon resonance sensor, this method does not require the noble metal film and keeps the same sensitivity, which is a low-cost alternative to refractive index sensing.

Precision metrology with weak measurements using spin splitting of light

Since its first introduction over twenty years ago, weak measurements have gradually became an useful metrology tool in the laboratory. Due to its desirable amplification effect, a small physical variable can be detected with weak measurements. Spin splitting of light, which stems from the interaction between the spin and orbital angular momentum in optical reflection or refraction at the interface of mediums, is always a weak effect. However, the spin splitting of light can be detected easily with weak measurements. Remarkably, the spin splitting of light is sensitive to the physical parameter variations of system. Using the spin splitting as a probe, the physical parameter can be accurately estimated with weak measurements. Here, we review some of our works on precision metrology with weak measurements using the spin splitting of light as a probe, such as estimation of the magneto-optical constant of a magnetic film, determination of the focused beam waist, and measurement of the polarization state of light.