[Article] Analysis of a wavelength-tunable D-shaped photonic crystal fiber filter with broad bandwidth
link: https://doi.org/10.1364/JOSAB.421792
Doi: 10.1364/JOSAB.421792
Thanks in Advance
The color of photonic crystal‐coated polydimethylsiloxane kirigami sheets (PhC‐PDMS kirigami) can be switched mechanically. The material offers programmable structural color, which is retained after recycling >10 000 times. The visibility of PhC‐PDMS kirigami is high—even in bright sunlight—and technical flexibility and mechanical durability are achieved.
Abstract
Bioinspired dynamic structural color has great potential for use in dynamic displays, sensors, cryptography, and camouflage. However, it is quite rare for artificial structural color devices to withstand thousands of cycles. Male hummingbird's crowns and gorgets are brightly colored, demonstrating frequent color switching that is induced by regulating the orientation of the feathers through movement of skin or joints. Inspired by this unique structural color modulation, we demonstrate a flexible, mechanically triggered color switchable sheet based on a photonic crystal (PhC)‐coated polydimethylsiloxane (PDMS) kirigami (PhC‐PDMS kirigami) made by laser cutting. Finite element modeling (FEM) simulation reveals that the thickness of PDMS kirigami and the chamfer at the incision induced by laser cutting both dominate the out‐of‐plane deformation through in‐plane stretching. The bioinspired PhC‐PDMS kirigami shows precisely programmable structural color and keeps the color very well after recycling over 10 000 times. This bioinspired PhC‐PDMS kirigami also shows excellent viewability even in bright sunlight, high readability, robust functionality, technical flexibility, and mechanical durability, which are readily exploitable for applications, such as chromic mechanical monitors for the sports industry or for medical applications, wearable camouflage, and security systems.
https://ift.tt/3sORKFa
Until recent years, it was unknown how chameleons changes the color of their skin. Chameleon's skin has a superficial layer which contains pigments, and under it, it have two layers that contains cells with guanine crystals. By different stimulation, such as heat and attraction, chameleons can change their color by altering the distance between the guanine crystals, which changes the wavelength of light reflected off the crystals. When excited, crystal spacing is the furthest apart (emits a red color) and when relaxed, crystal spacing is minimum (emits a green/blue color).
Research paper: https://www.nature.com/articles/ncomms7368
Smart molecular crystals with light‐driven mechanical responses have received intense interest owing to their potential uses in developing novel molecular machines, artificial muscles, and biomimetics. However, challenges remain in control over both the dynamic photo‐mechanical behaviors and static photonic properties of molecular crystals that are based on the same molecule. Herein, we illustrate that the construction of isostructural co‐crystals is an effective approach to tune on/off their light‐induced cracking and jumping behaviors (photosalient effect). The hydrogen‐bonded co‐crystals organized from 4‐(1‐naphthylvinyl)pyridine ( NVP ) along with co‐formers (tetrafluoro‐4‐hydroxybenzoic acid ( THA ) and tetrafluorobenzoic acid ( TA )) crystallize as isostructural crystals, but have notably different static and dynamic photo‐mechanical behaviors. These differences are due to alternations in the relative orientation of NVP and hydrogen‐bonding modes of the included co‐formers. After light activation, the 1D NVP‐TA crystal splits and shears off within 1 second, as a result from [2+2] cycloaddition of the olefin pair in NVP . For NVP‐THA , its photostability and high quantum yield endow the 1D microstructure with novel photonic properties, including low optical waveguide loss (0.066 dB µm −1 ), highly polarized anisotropy ( r =0.72) and efficient up‐conversion fluorescence. Therefore, this work not only provides an isostructural hydrogen‐bonded co‐crystal strategy to manipulate light‐induced dynamic movement and static photonic properties within 1D crystalline microstructures, but also affords a deep understanding regarding the role of hydrogen bonding in the construction of microscopic optical–mechanical responses in molecular systems.
https://ift.tt/2ERQqh0
We have just made available a package for the efficient simulation of photonic crystals - optical structures that "mold" the propagation of light in a number of different, useful ways. Moreover, we have also included an automatic differentiation backend, which allows the user to efficiently compute gradients of all output quantities (e.g. eigenmode frequencies and field profiles) with respect to all input parameters. https://github.com/fancompute/legume/
Our package can certainly be of use to researchers working with optical gratings or photonic crystal slabs. However, what we are even more excited about is the general idea of using automatic differentiation for the simulation of physical systems. Packages like TensorFlow and PyTorch, which have become extremely sophisticated in the past decade largely because of machine learning, are, in their core, just autodiff libraries. We can use these to "backprop" through a physical simulation, and perform really complicated optimizations with a large number of free parameters. This could be a game changer for next-generation devices, in photonics and beyond!
Microfabrication of circuits by combining the mechanical and photonic properties of flexible crystals is imperative for flexible miniature photonic devices. The fundamental understanding of molecular packing and energetics of intermolecular interactions is imperative to design such crystals with intrinsic flexibility and optical attributes. We present a rare one‐dimensional optical waveguiding crystal of dithieno[3,2‐a:2′,3′‐c]phenazine( 1 ) with high aspect ratio displaying high mechanical flexibility and selective self‐absorbance of the blue part of its fluorescence (FL). Though, macrocrystals exhibit elasticity, microcrystals deposited at a glass surface behave incredibly like plastic crystals due to significant surface adherence energy, making them suitable for constructing photonic circuits via micromechanical operation with atomic force microscopy cantilever tip. Phenomenally, the flexible crystalline waveguides display optical path‐dependent FL signals at the output termini in both straight and bend configuration suitable for wavelength division multiplexing technologies. A futuristic reconfigurable directional coupler fabricated via micromanipulation by combining two arc‐shaped crystals split the optical signal via evanescent coupling and deliver the signals at two output terminals with different split ratios. The presented mechanical micromanipulation technique could also be effectively extended to any flexible crystals to design and carve complex photonic circuits.
https://ift.tt/3fEIPjz
I read that photonic-crystal fibers use diffraction to send multiple wavelengths of light down it's core so that multiple information can be transmitted at once. How exactly does diffraction happen with the solid and the hollow cores? Or have I misunderstood something, and it uses total internal reflection?
Dynamic color is essential for practical applications such as dynamic displays, sensors, cryptography, and camouflage. In their Communication (DOI: 10.1002/anie.202103045), Mingzhu Li and co‐workers demonstrate a flexible, mechanically triggered color switchable sheet based on a photonic crystal‐coated polydimethylsiloxane kirigami (PhC‐PDMS kirigami) inspired by the structural color modulation of the male hummingbirds. The PhC‐PDMS kirigami shows precisely programmable structural color and keeps the color very well after recycling over 10,000 times.
https://ift.tt/3xOtZ36
Bioinspired dynamic structural color has great potential for use in dynamic displays, sensors, cryptography, and camouflage. However, it is quite rare for artificial structural color devices to withstand thousands of cycles. Male hummingbird’s crowns and gorgets are brightly colored, demonstrating color switching frequently that is induced by regulating the orientation of the feathers through movement of skin or joint. Inspired by this unique structural color modulation, we demonstrate a flexible, mechanically triggered color switchable sheet based on a photonic crystal‐ (PhC) coated polydimethylsiloxane (PDMS) kirigami (PhC‐PDMS kirigami) made by laser cutting. Finite element modeling (FEM) simulation reveals that the thickness of PDMS kirigami and the chamfer at the incision induced by laser cutting both dominate the out‐of‐plane deformation through in‐plane stretching. The bioinspired PhC‐PDMS kirigami shows precisely programmable structural color and keeps the color very well after recycling over 10,000 times. This bioinspired PhC‐PDMS kirigami also shows excellent viewability even in bright sunlight, high readability, robust functionality, technical flexibility, and mechanical durability, which are readily exploitable for applications, such as chromic mechanical monitors for the sports industry or for medical applications, wearable camouflage, and security systems.
https://ift.tt/3sORKFa
We have just made available a package for the efficient simulation of photonic crystals - optical structures that "mold" the propagation of light in a number of different, useful ways. Moreover, we have also included an automatic differentiation backend, which allows the user to efficiently compute gradients of all output quantities (e.g. eigenmode frequencies and field profiles) with respect to all input parameters. https://github.com/fancompute/legume/
https://preview.redd.it/lw9tsem0hjk41.png?width=3330&format=png&auto=webp&s=78356316f5c63b19e36d928e318ee1752cb9e2f1
Our package can certainly be of use to researchers working with optical gratings or photonic crystal slabs. However, what we are even more excited about is the general idea of using automatic differentiation for the simulation of physical systems. Packages like TensorFlow and PyTorch, which have become extremely sophisticated in the past decade largely because of machine learning, are, in their core, just autodiff libraries. We can use these to "backprop" through a physical simulation, and perform really complicated optimizations with a large number of free parameters. This could be a game changer for next-generation devices, in photonics and beyond!
Paper: https://arxiv.org/abs/2003.00379
Docs: https://legume.readthedocs.io/en/latest/
P. S. Our package uses Autograd, which is an autodiff extension of NumPy and SciPy.
