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Medical Physics Aug 2022Cherenkov radiation carries the potential of direct in-water dose measurements, but its precision is currently limited by a strong anisotropy. Taking advantage of...
PURPOSE
Cherenkov radiation carries the potential of direct in-water dose measurements, but its precision is currently limited by a strong anisotropy. Taking advantage of polarization imaging, this work proposes a new approach for high-accuracy Cherenkov emission dose measurements.
METHODS
Cherenkov radiation produced in a 15 × 15 × 20-cm water tank is imaged with a cooled charge-coupled device (CCD) camera from four polarizer transmission axes [0, 45, 90, 135°]. The water tank is positioned at the isocenter of a 5 × 5-cm , 6-, and 18-MV photon beam. Using Malus' law, the polarized portion of the signal is extracted. Corrections are applied to the polarized signal following azimuthal and polar Cherenkov emission angular distributions extracted from Monte Carlo simulations. Projected percent depth dose and beam profiles are measured and compared with the prediction from a treatment planning system (TPS).
RESULTS
Corrected polarized signals on the central axis reduced deviations at depth (mean ± standard deviation) from 8% ± 5% to 0.8% ± 1% at 6 MV and 8% ± 7% to 1% ± 3% at 18 MV. For the profile measurement, differences between the corrected polarized signal and the TPS calculations are 1% ± 3% and 2% ± 3% on the central axis at 6 and 18 MV respectively. In these conditions, Cherenkov emission is shown to be partly polarized.
CONCLUSIONS
This work proposes a novel polarization imaging approach enabling high-precision water-based dose measurements using the Cherenkov radiation. The method allows a correction of the Cherenkov emission anisotropy within 4% on the beam central axis and in depth.
PubMed: 35502867
DOI: 10.1002/mp.15693 -
Small GTPases 2013Epithelial cells differentiate and polarize to build complete epithelial organs during development. The study of epithelial morphogenesis is instrumental to the...
Epithelial cells differentiate and polarize to build complete epithelial organs during development. The study of epithelial morphogenesis is instrumental to the understanding of disease processes where epithelial polarity is disrupted. Recently, we demonstrated that matrix-induced cell confinement controls the acquisition of three-dimensional epithelial polarity, by modulating the initiation of the apical membrane to form a central lumen (J Cell Biol 2012; 198:1011-1026). Cell confinement can be achieved by use of micropatterned culture chips that allow precise micrometric-scale control of the cell adhesion surface and its composition. Using micropattern chips, we demonstrated that polarizing epithelial cells require high confinement conditions to properly position the centrosome and the trafficking machinery toward the cell-cell contacts and to initiate lumen morphogenesis. Low confinement induces LKB1 and RhoA-mediated cell contractility, which inhibits this mechanism for lumen formation. Deactivation of Myosin-II-mediated contractility rescued normal lumen initiation in low confinement conditions. Our results indicate that a mechanotransduction pathway coordinates nuclear and centrosome positioning to initiate epithelial morphogenesis. Here we discuss the potential candidates that control this process, specifically the polarized activation of Rho and Rab-family GTPases, and also a group of recently characterized nuclear transcription factors.
Topics: Animals; Cell Communication; Centrosome; Epithelial Cells; Laminin; Morphogenesis
PubMed: 23511851
DOI: 10.4161/sgtp.24303 -
Scientific Reports Aug 2023As society becomes smarter, advanced optical sensing and imaging technologies utilizing visible and near-infrared regions have become increasingly prevalent. Wire-grid...
As society becomes smarter, advanced optical sensing and imaging technologies utilizing visible and near-infrared regions have become increasingly prevalent. Wire-grid polarizers, which are available for broadband electromagnetic waves, are effective in improving the signal-to-noise ratio of such optical systems and enabling more advanced object detection and analysis. However, to be implemented in everyday products, low-cost manufacturing methods must be developed while maintaining high-performance optical functions. To meet these requirements, we conducted an analysis of the geometry of wire-grid polarizers, and designed and developed a wire-grid polarizer with a nano-triangular wave-shaped structure that can be fabricated using general-purpose manufacturing equipment. Once the mould is prepared, this polarizer can be fabricated via nanoimprinting and metal deposition with a normal angle or electroless plating processes. The polarizer fabricated through electroless Ni plating achieves a transmittance of 40%, which is approximately 1.4 times higher than that achieved in a previous study using electroless Ni plating on a rectangular structure with the same period. In addition, the polarizer fabricated through normal angle Al deposition operates over a wide range of wavelengths from visible light to near-infrared, and achieves a polarization extinction ratio of 24 dB at a wavelength of 550 nm and a high transmittance of 81%. High-performance polarizers can be obtained through normal-angle deposition using general-purpose equipment in contrast to the oblique-angle deposition method employed in the manufacture of conventional rectangular structure-based wire-grid polarizers, thereby contributing to cost reduction and improved manufacturability.
PubMed: 37591973
DOI: 10.1038/s41598-023-40511-z -
Applied Optics Oct 2023Polarizers are used to eliminate the undesired polarization state and maintain the other one. The phase change material (GSST) has been widely studied for providing...
Polarizers are used to eliminate the undesired polarization state and maintain the other one. The phase change material (GSST) has been widely studied for providing reconfigurable function in optical systems. In this paper, based on a silicon waveguide embedded with a GSST, which is able to absorb light by taking advantage of the relatively large imaginary part of its refractive index in the crystalline state, a multifunctional polarizer with transverse electric (TE) and transverse magnetic (TM) passages has been designed. The interconversion between the two types of polarizers relies only on the state switching of GSST. The size of the device is 7.5µ∗4.3µ, and the simulation results showed that the extinction ratio of the TE-pass polarizer is 45.37 dB and the insertion loss is 1.10 dB at the wavelength of 1550 nm, while the extinction ratio (ER) of the TM-pass polarizer is 20.09 dB and the insertion loss (IL) is 1.35 dB. For the TE-pass polarizer, a bandwidth broader than 200 nm is achieved with >20 and <2.0 over the wavelength region from 1450 to 1650 nm and for the TM-pass polarizer, >15 and <1.5 in the wavelength region from 1525 to 1600 nm, with a bandwidth of approximately 75 nm.
PubMed: 38038097
DOI: 10.1364/AO.503268 -
Frontiers in Sports and Active Living 2023The use of sunglasses and polarized sunglasses is common in all aspects of life and is very popular in outdoor athletic activities. However, the choice of athletes...
The use of sunglasses and polarized sunglasses is common in all aspects of life and is very popular in outdoor athletic activities. However, the choice of athletes regarding their sunglasses is often not dictated by the performance ensured by one model rather than another but by other factors such as look or wearability due also to the lack of technical data on cataloguess. A conscious choice of filters to use, also according to road and weather conditions, supported by quantitative data, would instead allow athletes to improve their visual comfort and sport experience. The transmission spectra of 10 pairs of sports sunglasses (five polarized and five not polarized) were measured and related to the road luminance for different sun positions in both horizontal and vertical polarizations. The luminous transmission factor was calculated, and the luminance quantities while wearing the glasses were defined and calculated for all cases. A survey was submitted to a group of athletes to collect their impressions and relate them to the measurement results. The pairs of polarized and non-polarized sports sunglasses showed similar transmission factors, so their ability to mitigate outdoor light is almost the same-the main difference lies in the polarized light transmitted. Outdoor measurements showed that the light reflected by the road has a substantial polarized horizontal component. Polarized sunglasses block much of the light reflected by the road, resulting in a darker appearance of the road and reducing the glare of the scene in bright sunlight. The decrease in road luminance increases the contrast discrimination of other objects in the scene, which reflect sunlight in a non-polarized way (e.g., non-flat surfaces). The survey demonstrates that interviewed athletes prefer polarized sunglasses for these aformentioned reasons. This study highlights the advantages of polarizing sunglasses for athletic activities on roads because the road surface often reflects polarized light depending on the position of the sun.
PubMed: 37608966
DOI: 10.3389/fspor.2023.1236473 -
Optics Express Nov 2023Integrated silicon nitride polarizers play a critical role in the design of complex integrated devices such as filters, switches, and large Mach-Zehnder interferometer...
Integrated silicon nitride polarizers play a critical role in the design of complex integrated devices such as filters, switches, and large Mach-Zehnder interferometer networks. These devices require precise control of both polarizations on a single circuit. In addition, polarizers are essential to accurately characterize these devices, primarily due to the low efficiency and polarization extinction ratio (PER) of the surface coupling gratings used in CMOS-compatible silicon nitride platforms for test-specific optical I/O. In this article, we present the design and experimental performance of six prototypes of TE-reflector/TM-pass polarizers specifically optimized for the C-band. These prototypes resemble subwavelength gratings with several additional intricate aspects. In particular, the longer prototypes feature two distinct regions, one representing non-intuitive tapers and the other showcasing a more distinct subwavelength grating. We achieve a high TM transmission efficiency of -0.28 dB along with a PER of 18.2 dB. These results are obtained with a device occupying an area as low as 11 µm × 2 µm, setting a new performance benchmark for compact polarizers compatible with standard silicon nitride platforms.
PubMed: 38017909
DOI: 10.1364/OE.503124 -
Materials (Basel, Switzerland) Aug 2022The modification of apolar carbon materials by heteroatom doping is an effective method that can effectively improve the surface polarity of carbon materials. In the...
The modification of apolar carbon materials by heteroatom doping is an effective method that can effectively improve the surface polarity of carbon materials. In the main body of the lithium-sulfur battery cathode, the structural properties of the carbon material itself with porous structure and large specific surface area provide sufficient space for sulfur accommodation and mitigate the bulk effect of the sulfur cathode (79%). The polarized surface of the reconstructed carbon material possesses strong adsorption effect on LiPs, which mitigates the notorious "shuttle effect." In this paper, the surface structure of the Ketjen black cathode body was reconstructed by B and N double heteroatoms to polarize it. The modified polarized Ketjen black improves the adsorption and anchoring ability of LiPs during the reaction and accelerates their kinetic conversion, while its own uniformly distributed small mesopores and oversized BET structural properties are beneficial to mitigate the bulk effect of sulfur cathodes. Lithium-sulfur batteries using B and N modified cathodes have an initial discharge capacity of 1344.49 mAh/g at 0.1 C and excellent cycling stability at 0.5 C (381.4 mAh/g after 100 cycles).
PubMed: 36013810
DOI: 10.3390/ma15165674 -
Nanomaterials (Basel, Switzerland) Dec 2022Optical anisotropy offers an extra degree of freedom to dynamically and reversibly regulate polarizing optical components, such as polarizers, without extra energy...
Optical anisotropy offers an extra degree of freedom to dynamically and reversibly regulate polarizing optical components, such as polarizers, without extra energy consumption and with high modulating efficiency. In this paper, we theoretically and numerically design broadband and incident-angle-modulation near-infrared polarizers, based on the SnSe, whose optical anisotropy is quantitatively evaluated by the complete dielectric tensor, complex refractive index tensor, and derived birefringence (~|Δ| = 0.4) and dichroism (~|Δ| = 0.4). The bandwidth of a broadband polarizer is 324 nm, from 1262 nm to 1586 nm, with an average extinction ratio above 23 dB. For the incident-angle-modulation near-infrared polarizer, the high incident angles dynamically and reversibly modulate its working wavelength with a maximum extinction ratio of 71 dB. Numerical simulations and theoretical calculations reveal that the considerable absorption for p light and continuously and relatively low absorption of s light lead to the broadband polarizer, while the incident-angle-modulation one mainly arises from the blue shift of corresponding wavelength of p light's minimum reflectance. The proposed novel design of polarizers based on SnSe are likely to be mass-produced and integrated into an on-chip system, which opens up a new thought to design polarizing optical components by utilizing other low-symmetry materials.
PubMed: 36616044
DOI: 10.3390/nano13010134 -
Optics Letters Mar 2021On-chip silicon polarizers have been widely used in polarization controllers. However, there is limited research on all-silicon polarizer covering the whole optical...
On-chip silicon polarizers have been widely used in polarization controllers. However, there is limited research on all-silicon polarizer covering the whole optical communication band due to the strong waveguide dispersion for silicon waveguides. In this Letter, we demonstrated an all-silicon TE polarizer with high polarization extinction ratio and low insertion loss, working for the whole optical communication band. The device is based on a shallow-etched waveguide realized on a silicon-on-insulator (SOI) platform. The optical field of TE polarization is designed to be tightly confined in the shallow-etched silicon waveguide, while that of TM polarization is weakly confined. As a result, TE polarization propagates through the waveguide with low loss, while TM polarization leaks into the substrate and decays finally. The measurements show that a maximum insertion loss <0.25 and polarization extinction ratio ()>20 over an ultrabroad operation band from 1260-1675 nm have been achieved for the proposed polarizer.
PubMed: 33720177
DOI: 10.1364/OL.416929 -
Sensors (Basel, Switzerland) Sep 2018Fiber-optic surface plasmon resonance (SPR) sensors possess the advantages of small size, flexible, allowing for a smaller sample volume, easy to be integrated, and high...
Fiber-optic surface plasmon resonance (SPR) sensors possess the advantages of small size, flexible, allowing for a smaller sample volume, easy to be integrated, and high sensitivity. They have been intensively developed in recent decades. However, the polarizing nature of the surface plasmon waves (SPWs) always hinders the acquisition of SPR spectrum with high signal-noise ratio in wavelength modulation unless a polarizer is employed. The addition of polarizer complicates the system and reduces the degree of compactness. In this work, we propose and demonstrate a novel, polarization-independent fiber-optic SPR sensor based on a BK7 bi-prism with two incident planes orthogonal to each other. In the bi-prism, TM-polarized components of non-polarized incident lights excite SPWs on the first sensing channel, meanwhile the TE components and the remaining TM components are reflected, then the reflected TE components serve as TM components of incident lights for the second sensing channel to excite SPWs. Simulations show the proposed SPR structure permit us to completely eliminate the polarization dependence of the plasmon excitation. Experimental results agree well with the simulations. This kind of devices can be considered an excellent option for development of simple and compact SPR chemical sensors.
PubMed: 30248984
DOI: 10.3390/s18103204