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1. Color polarization demosaicking by a convolutional neural network

   https://doi.org/10.1364/OL.431919  

   Sun, Yuanyuan ; Zhang, Junchao ; Liang, Rongguang ( August 2021 , Optics Letters)

   To address color polarization demosaicking problems in polarization imaging with a color polarization camera, we propose a color polarization demosaicking convolutional neural network (CPDCNN), which has a two-branch structure to ensure the fidelity of polarization signatures and enhance image resolution. To train the network, we built a unique dual-camera system and captured a pairwise color polarization image dataset. Experimental results show that CPDCNN outperformances other methods by a large margin in contrast and resolution.

    

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2. Quasi-simultaneous Optical Flux and Polarization Variability of the Binary Super Massive Black Hole Blazar OJ 287 from 2015 to 2023: Detection of an Anticorrelation in Flux and Polarization Variability

   https://doi.org/10.3847/2041-8213/acfd2e  

   Gupta, Alok C ; Kushwaha, Pankaj ; Valtonen, Mauri J ; Savchenko, Sergey S ; Jorstad, Svetlana G ; Imazawa, Ryo ; Wiita, Paul J ; Gu, Minfeng ; Marscher, Alan P ; Zhang, Zhongli ; et al ( October 2023 , The Astrophysical Journal Letters)

   We study the optical flux and polarization variability of the binary black hole blazar OJ 287 using quasi-simultaneous observations from 2015 to 2023 carried out using telescopes in the USA, Japan, Russia, Crimea, and Bulgaria. This is one of the most extensive quasi-simultaneous optical flux and polarization variability studies of OJ 287. OJ 287 showed large amplitude, ∼3.0 mag flux variability, large changes of ∼37% in degree of polarization, and a large swing of ∼215° in the angle of the electric vector of polarization. During the period of observation, several flares in flux were detected. Those flares are correlated with a rapid increase in the degree of polarization and swings in electric vector of polarization angle. A peculiar behavior of anticorrelation between flux and polarization degree, accompanied by a nearly constant polarization angle, was detected from JD 2,458,156 to JD 2,458,292. We briefly discuss some explanations for the flux and polarization variations observed in OJ 287.

    

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3. Design of Integrated Visible-Light Polarization Rotators and Splitters

   https://doi.org/10.1364/FIO.2022.JTu5A.48  

   Sneh, Tal ; Hattori, Ashton ; Notaros, Milica ; Corsetti, Sabrina ; Notaros, Jelena ( January 2022 , Frontiers in Optics + Laser Science)

   Integrated polarization rotators and splitters are designed for the first time at visible wavelengths. Specifically, an adiabatic polarization rotator, an off-axis polarization rotator, and a mode-coupling polarization splitter are designed in a silicon-nitride platform.

    

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4. Analysis of signal-to-noise ratio of angle of polarization and degree of polarization

   https://doi.org/10.1364/OSAC.422541  

   Chen, Yingkai ; Zhu, Zhongmin ; Liang, Zuodong ; Iannucci, Leanne_E ; Lake, Spencer_P ; Gruev, Viktor ( April 2021 , OSA Continuum)

   Recent advancements in nanofabrication technology has led to commercialization of single-chip polarization and color-polarization imaging sensors in the visible spectrum. Novel applications have arisen with the emergence of these sensors leading to questions about noise in the reconstructed polarization images. In this paper, we provide theoretical analysis for the input and output referred noise for the angle and degree of linear polarization information. We validated our theoretical model with experimental data collected from a division of focal plane polarization sensor. Our data indicates that the noise in the angle of polarization images depends on both incident light intensity and degree of linear polarization and is independent of the incident angle of polarization. However, noise in degree of linear polarization images depends on all three parameters: incident light intensity, angle and degree of linear polarization. This theoretical model can help guide the development of imaging setups to record optimal polarization information.

    

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5. Polarization near dislocation cores in SrTiO3 single crystals: The role of flexoelectricity

   https://doi.org/10.1063/5.0202453  

   Cheng, Xiaoxing ; Wang, Bo ; Chen, Long-Qing ( March 2024 , Applied Physics Letters)

   Spontaneous polarization as large as ∼28 μC/cm2 was recently observed around the dislocation cores in non-polar SrTiO3 bulk crystals, and its origin was attributed to the flexoelectric effect, i.e., polarization induced by strain gradients. However, the roles of flexoelectricity, relative to other electromechanical contributions, and the nature of dislocations, i.e., edge vs screw dislocations in the induced polarization, are not well understood. In this work, we study the role of flexoelectricity in inducing polarization around three types of dislocation cores in SrTiO3: b=a(100) edge dislocation, b=a(110) edge dislocation, and b=a(010) screw dislocation, where b is the Burgers vector. For the edge dislocations, polarization can be induced by electrostriction alone, while flexoelectricity is essential for stabilizing the symmetric polarization pattern. The shear component of the flexoelectric tensor has a dominant effect on the magnitude and spatial distribution of the flexoelectric polarization. In contrast, no polarization is induced around the b=a(010) screw dislocation through either electrostriction or flexoelectricity. Our findings provide an in-depth understanding of the role of flexoelectricity in inducing polarization around dislocation cores and offer insights into the defect engineering of dielectric/ferroelectric materials.

    

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