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109. Vectorial adaptive optics

Author

He, Chao, Antonello, Jacopo, and Booth, Martin J.

Subjects
Physics - Optics
Abstract

Adaptive optics normally concerns the feedback correction of phase aberrations. Such correction has been of benefit in various optical systems, with applications ranging in scale from astronomical telescopes to super-resolution microscopes. Here we extend this powerful tool into the vectorial domain, encompassing higher-dimensional feedback correction of both polarisation and phase. This technique is termed vectorial adaptive optics (V-AO). We show that V-AO can be implemented using sensor feedback, indirectly using sensorless AO, or in hybrid form combining aspects of both. We validate improvements in both vector field state and the focal quality of an optical system, through correction for commonplace vectorial aberration sources, ranging from objective lenses to biological samples. This technique pushes the boundaries of traditional scalar beam shaping by providing feedback control of extra vectorial degrees of freedom. This paves the way for next generation AO functionality by manipulating the complex vectorial field.

Published
2021

110. Polarisation optics for biomedical and clinical applications: a review

Author

He, Chao, He, Honghui, Chang, Jintao, Chen, Binguo, Ma, Hui, and Booth, Martin J.

Subjects
Physics - Optics
Abstract

Many polarisation techniques have been harnessed for decades in biological and clinical research, each based upon measurement of the vectorial properties of light or the vectorial transformations imposed on light by objects. Various advanced vector measurement/sensing techniques, physical interpretation methods, and approaches to analyse biomedically relevant information have been developed and harnessed. In this review, we focus mainly on summarizing methodologies and applications related to tissue polarimetry, with an emphasis on the adoption of the Stokes-Mueller formalism. Several recent breakthroughs, development trends, and potential multi-modal uses in conjunction with other techniques are also presented. The primary goal of the review is to give the reader a general overview in the use of vectorial information that can be obtained by polarisation optics for applications in biomedical and clinical research.

Published
2021

111. Thermal cycle stability and microstructure of Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystals.

Author

Liang, Min, Xiong, Ruibin, Chen, Shuli, Wang, Zujian, Su, Bin, Su, Rongbing, Liu, Ying, and He, Chao

Subjects
SINGLE crystals, THERMOCYCLING, THERMAL stability, FERROELECTRIC crystals, PERMITTIVITY, LEAD titanate
Abstract

The Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) ferroelectric single crystals have been commercially available as important components in medical ultrasound transducers due to their excellent piezoelectric and electromechanical coupling performance. The variation in piezoelectric and dielectric properties of PMN-PT single crystals with ambient temperature is an important application indicator. In this work, the PMN-PT single crystals after direct current poling (DCP) and alternating current poling (ACP) were subjected to the cyclic thermal treatment process. The thermal cycling stability and microstructural changes in PMN-PT single crystals were investigated. The ACP single crystals exhibit a higher dielectric constant ε 33 T / ε 0 (6500–7600) and piezoelectric coefficient d33 (2100–2500 pC N−1) compared to the DCP single crystals (ε 33 T / ε 0 of 4100–5000, d33 of 1200–1300 pC N−1). Under thermal cycling at 60 °C, the DCP and ACP single crystals exhibit good thermal cycling stability after 150 cycles. Microstructural observations show that the domain structure of the DCP single crystals exhibits "staggered domain walls, inhomogeneous domain size, variety of domain structure," while the relatively homogeneous stripe-like domains were observed in the ACP single crystals. After thermal cycling, new fine striped domains appear in both the DCP and ACP single crystals due to the instability of rotated polarization, but the piezoelectric and dielectric properties are not greatly affected. This work provides an intensive understanding of the effects of thermal cycling on the domain structure, which is useful for applications. [ABSTRACT FROM AUTHOR]

Published
2024
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114. Titan's prevailing circulation might drive highly intermittent, yet significant sediment transport

Author

Comola, Francesco, Kok, Jasper, Lora, Juan, Cohanim, Kaylie, Yu, Xinting, He, Chao, McGuiggan, Patricia, Hörst, Sarah, and Turney, Francis

Subjects
Life Below Water
Abstract

Titan, the largest moon of Saturn, is characterized by gigantic linear dunes and an active dust cycle. Much like on Earth, these aeolian processes are caused by the wind-driven saltation of surface grains. It is still unclear, however, how saltation on Titan can occur despite the typically weak surface winds and the potentially cohesive surface grains. Here, we explore the hypothesis that saltation on Titan may be sustained at lower wind speeds than previously thought, primarily through granular splash rather than aerodynamic lifting of surface grains. We propose a saltation mass flux parameterization for Titan and use it to quantify sediment transport with a general circulation model. The results suggest that Titan's prevailing circulation can generate highly intermittent yet significant saltation, with mass fluxes of the order of 10^4 kg m^-1 year^-1, and that Titan dunes may be formed primarily by fine grains, approximately 0.1 mm in size.

Published
2022

128. Revealing complex optical phenomena through vectorial metrics

Author

He, Chao, Chang, Jintao, Salter, Patrick S., Shen, Yuanxing, Dai, Ben, Li, Pengcheng, Jin, Yihan, Thodika, Samlan Chandran, Li, Mengmeng, Tariq, Aziz, Wang, Jingyu, Antonello, Jacopo, Dong, Yang, Qi, Ji, Lin, Jianyu, He, Honghui, Elson, Daniel S., Zhang, Min, Ma, Hui, and Booth, Martin J.

Subjects
Physics - Optics
Abstract

Advances in vectorial polarisation-resolved imaging are bringing new capabilities to applications ranging from fundamental physics through to clinical diagnosis. Imaging polarimetry requires determination of the Mueller matrix (MM) at every point, providing a complete description of an object's vectorial properties. Despite forming a comprehensive representation, the MM does not usually provide easily-interpretable information about the object's internal structure. Certain simpler vectorial metrics are derived from subsets of the MM elements. These metrics permit extraction of signatures that provide direct indicators of hidden optical properties of complex systems, while featuring an intriguing asymmetry about what information can or cannot be inferred via these metrics. We harness such characteristics to reveal the spin-Hall effect of light, infer microscopic structure within laser-written photonic waveguides, and conduct rapid pathological diagnosis through analysis of healthy and cancerous tissue. This provides new insight for the broader usage of such asymmetric inferred vectorial information.

Published
2021

129. Haze Evolution in Temperate Exoplanet Atmospheres Through Surface Energy Measurements

Author

Yu, Xinting, He, Chao, Zhang, Xi, Hörst, Sarah M., Dymont, Austin H., McGuiggan, Patricia, Moses, Julianne I., Lewis, Nikole K., Fortney, Jonathan J., Gao, Peter, Kempton, Eliza M. -R., Moran, Sarah E., Morley, Caroline V., Powell, Diana, Valenti, Jeff A., and Vuitton, Véronique

Subjects
Astrophysics - Earth and Planetary Astrophysics
Abstract

Photochemical hazes are important opacity sources in temperate exoplanet atmospheres, hindering current observations from characterizing exoplanet atmospheric compositions. The haziness of an atmosphere is determined by the balance between haze production and removal. However, the material-dependent removal physics of the haze particles is currently unknown under exoplanetary conditions. Here we provide experimentally-measured surface energies for a grid of temperate exoplanet hazes to characterize haze removal in exoplanetary atmospheres. We found large variations of surface energies for hazes produced under different energy sources, atmospheric compositions, and temperatures. The surface energies of the hazes were found to be the lowest around 400 K for the cold plasma samples, leading to the lowest removal rates. We show a suggestive correlation between haze surface energy and atmospheric haziness with planetary equilibrium temperature. We hypothesize that habitable zone exoplanets could be less hazy, as they would possess high-surface-energy hazes which can be removed efficiently., Comment: 6 figures, 2 tables, 23 pages

Published
2021
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