Polarization State Rotation Research Articles

Polarization states and Stokes vortices of dual Butterfly-Gauss vortex beams with uniform polarization in uniaxial crystals

We propose dual Butterfly-Gauss vortex beams with uniform polarization, which are composed of two finite-energy Butterfly-Gauss beams with vortex cores. Based on the paraxial vector theory, the analytical propagation expressions of the proposed beams in uniaxial crystals orthogonal to the optical axis are derived and used to investigate the evolutions of autofocusing behavior, polarization states and Stokes vortices. The results show that the autofocusing behavior and its autofocusing length can be affected by topological charge, and the input uniform polarization is disordered into non-uniform polarization owing to anisotropic diffraction. The symmetry and rotation of polarization states are also found for the case of vortex. The Stokes parameters on the Poincaré sphere can be manipulated by adjusting the refractive index ratio, azimuthal angle and phase retardation angle. Their Stokes vortices, e.g. S12 vortices, present the behavior of merging, separation and reversal. The presented work may be useful for manipulating polarization dynamics of catastrophe optical field in uniaxial crystal and has potential values in polarization-sensitive detection.

Polarization state and image rotation via spontaneously generated coherence in a spinning fast light medium

In this article we propose a four-level rubidium (Rb87) atomic system for observing interesting features of polarization state rotation in a fast light medium. We investigate spontaneously generated coherence (SGC) for a spinning medium. We show how SGC can affect different spectral profiles of the polarization state and images in this suggested model. We observe a 0.5 radian rotation and 2.5 microsecond time advancement in our proposed system. Our precise results will provide a new platform for researchers in quantum optics due to its applications in image coding, telecommunications and cloaking technology.

基于互补斯托克斯向量实现偏振态旋转的追踪和预测

基于互补斯托克斯向量实现偏振态旋转的追踪和预测

Gain-assisted superluminal propagation and rotary drag of photon and surface plasmon polaritons

Superluminal propagation of light is a well-established phenomenon and has motivated immense research interest that has led to state-of-the-art knowledge and potential applications in the emerging technology of quantum optics and photonics. This study presents a theoretical analysis of the gain-assisted superluminal light propagation in a four-level $N$-type atomic system by exploiting the scheme of electromagnetically induced gain and superluminal propagation of surface plasmon polaritons (SPPs) along the gain-assisted atomic-metal interface simultaneously. In addition, a theoretical demonstration is presented on the comparison between Fresnel's rotary photon drag and SPP drag in view of light polarization state rotation by rotating the coherent atomic medium and the atomic-metal interface, respectively. Analogous to photon drag in the superluminal anomalous dispersion region where light polarization rotation occurs opposite the rotation of the gain-assisted atomic medium, the rotation of the atomic-metal interface also rotates the polarization state of SPPs opposite the rotation of the interface. This further confirms the superluminal nature of SPPs propagating along the interface with negative group velocity. Rabi frequencies of the control and pump fields considerably modify both photon and SPP drag coefficients. Metal conductivity also controls SPP propagation.

All-fiber electric field sensor based on whispering-gallery-mode resonances in U-bent single-mode fibers integrated with liquid crystal

We propose an all-fiber electric field sensor using a U-bent single-mode fiber integrated with liquid crystal. The sensing mechanism is based on the interference between whispering-gallery modes and core mode in U-shaped bent fibers. We have experimentally investigated the influences of applied electric voltage as well as polarization state of the incident light on the transmission spectral characteristics of the proposed electric field sensor. The experimental results indicate that the transmission spectra are highly sensitive to the applied voltage and the highest sensitivity reaches 20.4221 nm/kV. The dip wavelengths and transmission loss at transmission dip exhibit a periodic variation behavior in response to the light polarization state rotation by 360 deg, which is in agreement with our theoretical analysis.

Coherent control of polarization state rotation via Doppler broadening and Kerr nonlinearity in a spinning fast light medium

We propose a four-level experimental N-type atomic configuration to observe the propagation of a light pulse in a spinning dispersive medium. In this model a fast propagating light pulse is observed in which the polarization states of the light and their transmitted images are rotated in the opposite direction to the spinning medium. We investigate the effects of Doppler broadening and Kerr nonlinearity on fast light propagation in a spinning medium. Doppler broadening and Kerr nonlinearity strongly influence the rotation of the polarization states of the light and images of fast light in a spinning medium. A pulse of group velocity −c/2000.5 ms−1 is enhanced to −c/80000 ms−1 due to the the Kerr effect and a significant increase is observed in the rotation of the polarization states of the light and images. At a specific parameter, a 25% fraction change is observed due to the Kerr effect. These results provide different rotation states for image coding.

Skew aberration: a form of polarization aberration

We define a new class of aberration, skew aberration, which is a component of polarization aberration. Skew aberration is an intrinsic rotation of polarization states due to the geometric transformation of local coordinates, independent of coatings and interface polarization. Skew aberration in a radially symmetric system has the form of a circular retardance tilt plus coma aberration. Skew aberration causes undesired polarization distribution in the exit pupil. We demonstrate statistics on skew aberration of 2383 optical systems described in Code V's U.S. patent library [Code V Version 10.3 (Synopsys, 2011), pp. 22-24]; the mean skew aberration is 0.89° and the standard deviation is 1.37°. The maximum skew aberration found is 17.45° and the minimum is -11.33°. U.S. patent 2,896,506, which has ±7.01° of skew aberration, is analyzed in detail. Skew aberration should be of concern in microlithography optics and other high NA and large field of view optical systems.

Magneto-optic fiber Sagnac modulator based on magnetic fluids

A magneto-optic modulator with a magnetic fluid film inserted into an optical fiber Sagnac interferometer is proposed. The magnetic fluid exhibits variable birefringence and Faraday effect under external magnetic field that will lead to a phase difference and polarization state rotation in the Sagnac interferometer. As a result, the intensity of the output light is modulated under the external magnetic field. Moreover, the modulator has a high extinction ratio and can easily be integrated in a single-mode fiber system. The performance of the modulator is not affected by ambient temperature variation from room temperature to 40 °C.

Polarization-Multiplexed Optical Wireless Transmission With Coherent Detection

In this paper, we propose, analyze, and experimentally verify polarization-multiplexed optical wireless transmission with coherent detection as a means of improving performance and increasing the per-wavelength data rate in the presence of atmospheric turbulence. It is first shown that in terrestrial last-mile applications, the polarization state changes of the optical wireless signal are governed by optical source properties both in the absence and in the presence of mild to moderately severe turbulence. Under these conditions, it is shown that the polarization evolution is reduced to a polarization state rotation wherein the cross-polarization interference can be equalized with well-known blind algorithms. We also experimentally verify the analytical findings, demonstrating 112 Gb/s POLMUX-QPSK transmission with coherent detection in a non-fading free-space channel, and numerically extend the experimental results to turbulent settings by invoking the lognormal model for turbulence-induced fading. Performance gains of 5-14 dB along with a doubling of the data rate through polarization multiplexing are exhibited compared to legacy single-polarization intensity modulation/direct detection (IM/DD) optical wireless systems. The presented analytical and experimental results indicate that the proposed approach is promising for notably increasing the data rate in last-mile free-space optical transmission.

Optical generation of wide-band tunable millimetre-wave signals using PSRF

Analysis of the optical generation of three bands of continuously tunable millimeter-wave signals using an optical phase modulator (OPM) and an optical notch filter is presented. Three bands of millimeter-wave signals are tuned by using an optical phase modulator and a polarization state rotation filter (PSRF) as optical notch filter. The effect of the chromatic dispersion on wide-band continuously tunable millimeter-wave signal which using an OPM and a PSRF is investigated. The spectrum of the generated millimeter-wave signal after transmission over a 25 km standard single-mode fiber (SSMF) is obtained.

Polarization state rotation filter for optical generation of continuously tunable millimeter-wave signal employing an external intensity modulator

A method to generate a continuously tunable millimeter-wave signal employing an optical external intensity modulator and polarization state rotation filter (PSRF) is proposed. The technique is based on the optical heterodyne, the Mach–Zehnder modulator (MZM) is biased to suppress odd-order sidebands, and the polarization-dependent PSRF is used to filter the optical carrier. A concept-proof experiment system is built to demonstrate the generation of microwave signal by beating the generated two second-order optical components. The results show that a high purity tunable microwave signal with very narrow linewidth at four times the frequency of microwave drive signal can be obtained. Moreover, the generated signal does not suffer obvious phase-noise degradation after transmission through a 25-km SSMF link. The operation principle of PSRF and the effect of its performance on the generated electrical signal are also analyzed. The proposed technique based on PSRF is very easy to implement, flexible and cost-effective to generate continuously tunable millimeter-wave signals.

High carrier suppression double sideband modulation using polarization state rotation filter and optical external modulator

We propose a high carrier suppression double sideband modulation technique using a Mach–Zehnder modulator (MZM) and an integrated polarization state rotation filter (PSRF), which is designed to improve the carrier suppression ratio. With the functions of MZM and PSRF, about 30dB carrier suppression ratio relative to first-order sidebands is demonstrated. Moreover, we demonstrate the optical generation of microwave/millimeter-wave signals by beating the carrier suppressed double sideband (DSB-SC) lightwave signals. The experimental results show that the improvement of carrier suppression ratio with PSRF can effectively cancel the modulating RF frequency component. A tunable and high purity microwave signal, which is limited by the bandwidth of MZM and photodetector (PD), is obtained, and it does not suffer from obvious phase noise degradation with 25km transmission.

Optically induced polarization rotations in CdTe/CdMnTe multiple quantum wells

We report large polarization state rotations of a weak pulsed beam in CdTe/CdMnTe quantum wells photoinduced by intense circularly polarized pulsed pump beam. Time-resolved analysis of the effect shows that, at moderate pump fluences, the polarization state rotation is due to the combined effect of many-body interactions and spectral hole burning at early times and to photoinduced magnetization at longer ones. At higher pump fluences, space filling and degenerate four-wave mixing become important. At low pump fluences (few μJ/cm2) already the polarization rotation photoinduced at early times can be as large as a few degrees making these multiple quantum wells potential candidates for applications.

Coherent optical fiber communications system using all-optical correlation processing

We propose a point-to-point or single-ended communications technique based on single-mode optical fibers that uses all-optical pulse multiplexing at the transmitter and coherent optical correlation at the receiver. This technique shows potential for application to secure untappable communications, fiber local-area networks, and optical ranging in the presence of a strong white-light background. The system can employ a low-coherence source, is insensitive to source phase noise and polarization-state rotation in the fiber link, and uses simple electronic threshold detection. Coherent correlation and anticorrelation are demonstrated experimentally, and practical requirements are examined.