Polarization Compensation Research Articles

Dual-Band Air-Like Transparent Slab by Full Polarization Compensation

Dual-Band Air-Like Transparent Slab by Full Polarization Compensation

Research on polarization compensation for practical satellite-based quantum key distribution

Satellite-based quantum key distribution (QKD) is one of the effective solutions for building a global-scale quantum network. For practical satellite-based polarization-encoding QKD systems, the polarization degradation introduced by the single-mode fiber and the relative rotation between satellites and ground stations will lead to a decrease in the polarization performance and need to be compensated. In this work, we propose two novel on-orbit satellite-to-ground joint polarization measurement and compensation methods, which can ensure high polarization fidelity while effectively saving hardware resources and reducing costs. By establishing a polarization compensation model and performing theoretical analysis, combined with desktop experimental verification, we demonstrated the effectiveness of the satellite-to-ground joint polarization compensation and achieved a low quantum bit error rate below 0.3% after background removal. The presented polarization compensation laid the foundation for the subsequent applications in satellite-based QKD and satellite-based quantum networks.

Real-time polarization compensation method in quantum communication based on channel Muller parameters detection

Polarization drift in fiber and free-space optical links is a major factor in the dynamic increase of bit error rate in polarization-coded quantum key distribution (QKD) systems. A dynamic polarization compensation method applicable to both links is a challenge. Here we propose a universally applicable real-time polarization compensation method, that the Muller parameters of the optical links are first detected using a polarization detector, and then the optimal parameters of the controller are obtained by gradient descent algorithm. Simulation results indicate advantages over current methods, with fewer waveplates, faster speed, and wider applicability for various optical links. In equivalent experiments of both satellite and fiber optical links, the average polarization extinction ratio of 27.9 dB and 32.2 dB are respectively achieved. The successful implementation of our method will contribute to the real-time polarization design of fiber and free-space QKD systems, while also contributing to the design of laser-based polarization systems.

Interferometric polarization compensation based on one single polarization-maintaining fiber.

In an interferometry system based on one single polarization-maintaining fiber (PMF), defects like the laser's ellipticity, the alignment error between the PMF and the laser source, and the PMF's internal stress will cause the emitted light from the PMF to be incompletely linearly polarized, resulting in nonlinear errors that cannot be ignored. This paper proposes a novel method that can realize polarization compensation for heterodyne interferometry, reduce the ellipticity of the emitted light, and thereby reduce the nonlinear error of the system. When using a PMF with an Extinction Ratio (ER) of 22 dB, the experimental results show that this method can reduce the polarization and increase the ER to 33.95 dB. After polarization compensation, the nonlinear error is reduced from 7.22 nm to 2.02 nm. The proportion of the nonlinear error reduction reaches to 71.99%, which greatly improves the accuracy of the system.

Prescriptive method for fiber polarization compensation in two bases.

Single-mode optical fibers exhibit a small but non-negligible birefringence that induces random polarization rotations during light propagation. In classical interferometry these rotations give rise to polarization-induced fading of the interferometric visibility, and in fiber-based polarimetric sensors as well as quantum optics experiments, they scramble the information encoded in the polarization state. Correcting these undesired rotations is consequently an important part of many experiments and applications employing optical fibers. In this Lab Note we review an efficient method for fully compensating fiber polarization rotations for general input states. This method was not originally devised by us, but does, to the best of our knowledge, not appear in the literature, and our interactions with the community have indicated that it is not well known.

Unravelling the band splitting origin in bulk and 2D distorted α-CsPbI3 perovskite.

Organic-inorganic hybrid perovskites have demonstrated versatile functionalities for optoelectronic, spintronic, and other applications. This Research focuses on the impact of structural distortion on band splitting and spintronic properties of bulk and 2D α-CsPbI3 for the first time. CsI- and PbI2-slabs were considered to reveal the role of surface termination on band splitting. It was shown that displacements in different site symmetries can lead to various band splittings. Finally, to adjust the band splitting, the external field was considered. The results unravel the polarization compensation owing to the distortion.

Density-matrix-formalism based scheme for polarization mode dispersion monitoring and compensation in optical fiber communication systems

Density-matrix-formalism based scheme for polarization mode dispersion monitoring and compensation in optical fiber communication systems

Enhanced Measurement of Vortex Beam Rotation Using Polarization-Assisted Particle Swarm Optimization for Phase Retrieval

In detecting the rotation velocity of an object employing the rotational Doppler effect of vortex beams, atmospheric turbulence can easily cause phase distortion and spiral spectrum dispersion, consequently reducing velocity measurement accuracy. This study combines adaptive optical intelligence algorithms with polarization compensation information to propose a novel approach, the Stokes–Particle swarm optimization Gerchberg–Saxton (Stokes-PSO GS) algorithm, which integrates Stokes polarization information assistance and PSO for GS phase retrieval. The algorithm adjusts the phase and amplitude of the pre-compensated phase screen of the GS algorithm utilizing Stokes information of polarized vortex beam (with lL = 5 and lR = −5) before and after distortion. The PSO is then employed to optimize the pre-compensated phase screen and perform compensations. Simulation results at zS-T = 200 m and Cn2 = 1 × 10−14 m−2/3, demonstrate that the Stokes-PSO GS algorithm exhibits strong stability (small angular spectrum purity deviation, σp, Stokes-PSO GS = 0.005675% < σp, GS = 11.62%), superior optical field recovery (well-recovered Stokes optical field, up to 33.76% improvement in angular spectrum purity), and high-velocity measurement accuracy (25.93% improvement) compared to the GS algorithm. This approach enables precise measurement of the rotation velocity of the vortex beam, demonstrating its potential in practical applications.

Hydrogen-mediated polarity compensation on the (110) surface terminations of ABO3 perovskites.

Polar surfaces undergo polarity compensation, which can lead to significantly different surface chemistry from their nonpolar counterparts. This process in turn can substantially alter the binding of adsorbates on the surface. Here, we find that hydrogen binds much more strongly to the polar (110) surface than the nonpolar (100) surface for a wide range of ABO3 perovskites, forming a hydroxyl layer on the O24- termination and a hydride layer on the ABO4+ termination of the (110) surface. The stronger adsorption on the polar surfaces can be explained by polarity compensation: hydrogen atoms can act as electron donors or acceptors to compensate for the polarity of perovskite surfaces. The relative stability of the surface terminations is further compared under different gas environments and several perovskites have been found to form stable surface hydride layers under oxygen-poor conditions. These results demonstrate the feasibility of creating stable surface hydrides on perovskites by polarity compensation which might lead to new hydrogenation catalysts based on ABO3 perovskites.

AI polarization compensation algorithm using a asymmetry entangled photon source

Satellite-based entanglement distribution is essential for global-scale practical quantum network and foundational tests of quantum physics. Owing to relative motion of the satellite and the ground station, however, using high intensity reference laser to compensate polarization rotation is necessary. Here we propose an artificial intelligence (AI) algorithm to compensate polarization using entangled photon pairs instead of high intensity reference laser. Our AI polarization compensation algorithm opens a new avenue to quantum communications and fundamental quantum optics experiments.

A study of polarization compensation for quantum networks

The information-theoretic unconditional security offered by quantum key distribution has spurred the development of larger quantum communication networks. However, as these networks grow so does the strong need to reduce complexity and overheads. Polarization-based entanglement distribution networks are a promising approach due to their scalability and no need for trusted nodes. Nevertheless, they are only viable if the birefringence of all-optical distribution fibres in the network is compensated to preserve the polarization-based quantum state. The brute force approach would require a few hundred fibre polarization controllers for even a moderately sized network. Instead, we propose and investigate four different realizations of polarization compensation schemes that can be used in quantum networks. We compare them based on the type of reference signals, complexity, effort, level of disruption to network operations and performance on a four-user quantum network.

Polarization-insensitive EDG demultiplexer combined with a polarization beam splitter.

Polarization dependence is an inherent challenge for wavelength-division multiplexing transceivers on silicon photonic platforms, causing severe problems with polarization-dependent losses and hindering the implementation of monolithic integrated receivers. In this study, we developed a polarization-insensitive demultiplexer on a silicon nitride (Si3N4) platform, which provides a promising solution to the polarization challenge. Comprising an etched diffraction grating (EDG) and a polarization beam splitter (PBS), the demultiplexer can achieve polarization insensitivity by introducing an additional optical path difference for polarization compensation. The fabricated demultiplexers were experimentally measured to have minimum insertion losses of 1.5 dB, cross talks of better than -25 dB, and polarization-dependent losses of better than 0.7 dB. This is the first, to the best of our knowledge, proposed solution for a polarization-insensitive EDG demultiplexer combined with a PBS on a Si3N4 platform.

Polarization Optical Design of 8-meter Chinese Giant Solar Telescope

Instrumental polarization is a vital factor for the accurate measurements of the solar magnetic field. It is necessary to optimize the optical design of the large solar telescope to obtain high accuracy solar magnetic field information. In this paper, an optimal design scheme based on four-mirror polarization compensation optics for the 8-meter giant solar telescope is presented. The polarization effect of pupil and field of view are analyzed by the polarization ray tracing programming, the telescope motion and wavelength properties of the field-effect are investigated detailedly. The result shows that, in the near infrared waveband which includes the magnetic sensitive spectral lines of He I 1.083 μm and Fe I 1.565 μm, the polarization-free field size is 0.91′, and the polarization-free field size in the visible band is 0.5′, in which the instrumental polarization of telescope is smaller than 2×10−4.

Fabrication of non-volatile memory transistor by charge compensation of interfacial ionic polarization of a ferroelectric gate dielectric

Lithium niobate (LiNbO3) is a popular lead free perovskite ferroelectric materials, but its implementation as a gate dielectric for developing a ferroelectric thin film transistor (FeTFT) has not been investigated much due to its low band gap. Low band gap introduces high gate leakage current that results in very low retention time of the device. In this report a solution processed Li5AlO4/LiNbO3/Li5AlO4 stacked layer has been used as a gate dielectric of a metal oxide thin film transistor which reduces gate leakage current by four orders of magnitude with respect to the single layer LiNbO3 gate dielectric device. Besides, due to the ionic polarization of Li5AlO4 thin film that originated from the mobile Li+, charge compensation of the depolarization field has been nearly removed. By reducing these factors, it becomes possible to fabricate metal oxide based FeTFT that has retention time of 7 h which is ∼200 times higher with respect to the LiNbO3 only FeTFT. The ratio of On and Off state of FeTFT is ∼103 which retains ∼ 95% after 7 h of operation. The carrier mobility, ON/OFF ratio and subthreshold swing (SS) of this FeTFT are 2.9 cm2 V − 1 s − 1,7.2 × 104 and 328 mV.decade−1 respectively.

Modulation of the LaFeO3 film growth by the terrace width of SrTiO3 substrates

We have investigated the growth of polar LaFeO3 thin films on SrTiO3 (001) substrates with various terrace widths by pulsed laser deposition. It is found that the growth of LaFeO3 films undergoes a transition from a two-dimensional (2D) mode to a three-dimensional (3D) mode due to polarity compensation. Notably, however, the critical thickness of the growth mode transition from 2D to 3D can be modulated by the terrace width of the substrate, i.e., when the film is 30 monolayers thick, it becomes 3D growth on the substrates with narrow terrace width (∼100 nm) while it maintains 2D growth on those with wide terrace width (∼400 nm). Combined with dynamic and kinetic models, we have found that the modulation of the critical thickness from 2D to 3D is rationalized as a result of competition between the dynamic process and the kinetic process. These findings highlight the key influence of substrate surface morphology on the epitaxial growth of complex oxide films, shedding light on the construction of multifunctional artificial low-dimensional structures with polar stackings.

Dual Sagnac Interferometer Distributed Optical Fiber Localization Method Based on Hilbert–Huang Transform

In order to solve the problem that the dual Mach Zehnder (M-Z) interferometer system is easily affected by external environmental noise, a data signal-processing scheme based on Hilbert–Huang transform (HHT) is proposed to achieve high-precision location with distributed optical fibers. The polarization compensation module has a built-in dual Sagnac interferometer system which is used to stabilize the polarization state of the Sagnac interferometer. The eigenmode function is obtained by empirical mode decomposition of the received two optical signals, and then the Hilbert spectrum is obtained by superimposing the Hilbert transform, so that the high-similarity curve caused by the vibration signal can be clearly and intuitively extracted. The optical signal information can be calculated based on the cross-correlation and delay estimation algorithm to accurately obtain the vibration position information. The experimental results show that the positioning accuracy can reach ±11 m, with a sensing fiber length of 15 km and a sampling rate of 10 MHz. It is proven that the distributed optical fiber sensing technology based on the dual Sagnac interferometer system has high practical application value.

Polarisation compensation in non-planar image-rotating OPO ring resonators.

Non-planar image-rotating OPO ring resonators necessitate polarisation compensation in contrast to their planar counterparts. This is essential for maintaining phase matching conditions for non-linear optical conversion in the resonator during each cavity round trip. In this study, we examine the polarisation compensation and its impact on the performance of two types of non-planar resonators: RISTRA with a π2 image rotation and FIRE with a fractional image rotation (π2 fraction). The RISTRA is insensitive to mirror phase shifts, while the FIRE has a more complex dependence of polarisation rotation on mirror phase shifts. There has been debate over whether a single birefringent element can provide adequate polarisation compensation for non-planar resonators beyond RISTRA-type. Our results show that under certain experimentally feasible conditions, even FIRE resonators can achieve adequate polarisation compensation with a single half-wave plate. We validate our theoretical analysis through numerical simulations and experimental studies of OPO output beam polarisation using ZnGeP2 non-linear crystals.

Thermodynamics of Light-Induced Nanoscale Polar Structures in Ferroelectric Superlattices.

We study the thermodynamics of nanoscale polar structures in PbTiO3/SrTiO3 ferroelectric superlattices induced by above-bandgap optical excitation using a phase-field model explicitly considering both structural and electronic processes. We demonstrate that the light-excited carriers provide the charge compensation of polarization bound charges and the lattice thermal energy, both of which are key to the thermodynamic stabilization of a previously observed supercrystal, a three-dimensionally periodic nanostructure, within a window of substrate strains, while different mechanical and electrical boundary conditions can stabilize a number of other nanoscale polar structures by balancing the competing short-range exchange interactions responsible for the domain wall energy and long-range electrostatic and elastic interactions. The insights into the light-induced formation and richness of nanoscale structures from this work offer theoretical guidance for exploring and manipulating the thermodynamic stability of nanoscale polar structures employing a combination of thermal, mechanical, and electrical stimuli as well as light.

Silicon-based decoder for polarization-encoding quantum key distribution

Silicon-based polarization-encoding quantum key distribution (QKD) has been widely studied, owing to its low cost and robustness. However, prior studies have utilized off-chip devices to demodulate the quantum states or perform polarization compensation, given the difficulty of fabricating polarized independent components on the chip. In this paper we propose a fully chip-based decoder for polarization-encoding QKD. The chip realizes a polarization state analyzer and compensates for the BB84 protocol without requiring additional hardware. It is based on a polarization-to-path conversion method that uses a polarization splitter-rotator. The chip was fabricated using a standard silicon photonics foundry; it has a compact design and is suitable for mass production. In the experimental stability test, an average quantum bit error rate of 0.59% was achieved through continuous operation for 10 h without any polarization feedback. Furthermore, using the developed feedback algorithm, the chip enabled the automatic compensation of the fiber polarization drift, which was emulated by a random fiber polarization scrambler. In the case of the QKD demonstration, we obtained a finite-key secret rate of 240 bps over a fiber spool of 100 km. This study represents an important step toward the integrated, practical, and large-scale deployment of QKD systems.

DFT＋U calculations on [formula omitted](100) surface: thermodynamic stability and polarity compensation

Employing the DFT+U framework we investigate the thermodynamic stability of U3O8(100) surface. The most stable structure is predicted to gradually turn from the under-stoichiometric 06- to the over-stoichiometric 56-slab as the oxygen chemical potential increases, showing a continuous surface oxidation process. Oxygen atoms are found to always firstly adsorb on the lower oxidized U ions. Due to the polarity compensation, significant modification of surface charge presents on considered terminations, which is transferred via both U-5f and O-2p states, implying the nature of U3O8 as an intermediate state between the Mott–Hubbard and charge-transfer materials. It is also shown that the displacement of the outmost U6O10 layer and the surface energy are strongly related to the redistribution of surface charge. The static effect between charged layers is the major factor which influences the layer displacement. The increase in surface energy is shown to be roughly linearly dependent on the amount of the surface charge transfer.