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Twins in YAl3(BO3)4 and K2Al2B2O7 Crystals as Revealed by Changes in Optical Activity
摘要： Many borate crystals feature nonlinear optical properties that allow for efficient frequency conversion of common lasers down into the ultraviolet spectrum. Twinning may degrade crystal quality and affect nonlinear optical properties, in particular if crystals are composed of twin domains with opposing polarities. Here, we use measurements of optical activity to demonstrate the existence of inversion twins within single crystals of YAl3(BO3)4 (YAB) and K2Al2B2O7 (KABO). We determine the optical rotatory dispersion of YAB and KABO throughout the visible spectrum using a spectrophotometer with rotatable polarizers. Space-resolved measurements of the optical rotation can be related to the twin structure and give estimates on the extent of twinning. The reported dispersion relations for the rotatory power of YAB and KABO may be used to assess crystal quality and to select twin-free specimens.
关键词： optical activity,inversion twin,YAB,optical rotatory dispersion,KABO,second harmonic generation,frequency conversion,K2Al2B2O7,NLO crystals,YAl3(BO3)4
更新于2025-10-22 19:40:53
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Contrast of optical activity and rogue wave propagation in chiral materials
摘要： We report the contrast of optical activity and properties of nonparaxial optical rogue waves for the higher-order nonparaxial chiral nonlinear Schr?dinger (NLS) equation. The latter describes the propagation of ultrashort optical pulses in chiral optical fibers. Both first- and second-order rogue wave solutions are investigated analytically by the modified Darboux transformation (MDT) and numerically by one pseudo-spectral method. The interplay of chiral materials on rogue wave propagation is elucidated, and the results can be applied on optical communication and in others physical systems.
关键词： Chirality and optical activity,Chiral optical fibers,Rogue wave propagation,Chiral materials
更新于2025-09-23 15:23:52
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Optically active polyaniline film based on cellulose nanocrystals
摘要： Chiral transfer from cellulose nanocrystals (CNCs) chiral nematic liquid crystal to polyaniline (PANI) is successfully achieved through co-assembly method for the first time, affording the PANI film based on CNCs optical activity. Meanwhile, the CNCs/PANI composite film displays notable Cotton effect ascribed to the polaron band transitions of PANI in circular dichroism (CD) spectrum. Hydrogen bond and electrostatic attraction favor the combination of two molecular chains in the mixed aqueous suspension and will lead to the chiral assembly of the PANI in the host chiral nematic film. However, the CD signal disappears when cholesteric phase collapse by acid protonation, and which demonstrates the chiral nematic ordering of the CNCs is essential to the chiral transfer. With the assistance of CNCs, PANI chains form a helically stacked structure. Thus, the optical activity of PANI originates from its long range organization.
关键词： co-assembly,chiral transfer,polaron transition,optical activity,Cotton effect
更新于2025-09-23 15:23:52
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Encyclopedia of Spectroscopy and Spectrometry || Surface-Enhanced Raman Optical Activity (SEROA)
摘要： This review discusses research into the enhancement of the chiroptical spectroscopic technique of Raman optical activity (ROA) through plasmonic resonance effects. The sensitivity of ROA spectroscopy to molecular stereochemistry and conformational dynamics has led to its increasing use in biology and the pharmaceutical sciences. However, the relative weakness of the ROA scattering process, being typically three to five orders of magnitude lower than the parent Raman scattering, has limited its application to conditions of relatively high concentrations and data accumulation times. The potential solution to this limitation in ROA by using the surface plasmon resonances that give rise to surface-enhanced Raman scattering (SERS) in order to boost ROA spectral intensity has been recognized by many researchers. Frustratingly, reliable measurement of this new technique of surface-enhanced Raman optical activity (SEROA) proved challenging to accomplish. A previous review by Abdali and Blanch presented the challenges involved in attempts to measure SEROA, as well as early results. Since then, significant advances have been made in exploring the SEROA phenomenon, and the time is appropriate for an updated account of this work. In order to provide sufficient background for guiding readers into the underlying principles of, and challenges faced in, measuring SEROA, we begin with an introduction to ROA before progressing on to its plasmonically-enhanced form.
关键词： chiroptical spectroscopy,SEROA,ROA,plasmonic resonance,Surface-Enhanced Raman Optical Activity,Raman Optical Activity,SERS,surface-enhanced Raman scattering
更新于2025-09-23 15:21:21
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[IEEE 2018 9th International Conference on Ultrawideband and Ultrashort Impulse Signals (UWBUSIS) - Odessa, Ukraine (2018.9.4-2018.9.7)] 2018 9th International Conference on Ultrawideband and Ultrashort Impulse Signals (UWBUSIS) - A Way to Realize a Multi-Frequency Polarization Plane Rotator
摘要： In this paper, we propose a simple design of a planar-chiral screen based polarization plane rotator that enables a polarization conversion at two assigned frequency bands simultaneously. The rotator is composed of a pair of conjugated double periodic perforated screens separated by a short distance. Two groups of four rectangular slots are cut along a perimeter of the screen periodical cell. Polarization rotation frequencies are controlled by choosing appropriated dimensions and placements of the slots’ groups. At the same time, we report that even a rotator with equal slots belonging to different (outer or internal) quadruples enables a dual-frequency operation as well.
关键词： optical activity,frequency-selective surface,rotator,polarization conversion
更新于2025-09-23 15:21:21
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Born-Kuhn model for magnetochiral effects
摘要： This study focuses on theoretical and numerical investigations of the magnetochiral (MCh) effect in the optical region. Electrodynamics in a medium with broken time and space inversions is described by two orthogonal coupled oscillators, in what is known as the Born-Kuhn model, subject to an external static magnetic field. Constitutive equations and the refractive index of the medium are theoretically derived. The results show that the MCh effect is induced even in the absence of an intrinsic interaction between the magneto-optical effect and the optical activity. The study also numerically investigates the electromagnetic response in a metamaterial with magnetism and chirality in the deep ultraviolet region. The results agree well with the main results of our theory. This paper paves the way to realizing MCh metamaterials in the optical region.
关键词： optical activity,magnetochiral effect,metamaterials,Born-Kuhn model,magneto-optical effect
更新于2025-09-23 15:21:01
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The role of plasmonic excitations in the optical activity of periodic structures with configurational chirality
摘要： Broken mirror symmetry of chiral structures imposes a lack of mirror symmetry in the scattering pro?le. When an energy dissipation channel is introduced in the system, an overall optical activity arises. Plasmonic nanostructures, therefore, are an ideal platform to induce optical activity by means of constitutional or con?gurational chirality. We experimentally investigate the mechanism of plasmonically induced con?gurational chirality in a periodic monoclinic hole array with a broken mirror symmetry. The resulting optical activity of the structure is studied by using k-space leakage radiation measurements.
关键词： k-space leakage radiation measurements,plasmonic excitations,periodic structures,optical activity,configurational chirality
更新于2025-09-23 15:21:01
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Self-Assembled Nanohelix for White Circularly Polarized Luminescence via Chirality and Energy Transfer
摘要： Chiral nanostructures and their optical activity have been attracting great interest. Here, we designed enantiomer bolaamphiphile containing a naphthalene moiety (bola-1) and alkyl spacer, and investigated their self-assembly as well as optical activity. It was found the compound could form gels in various organic or mixed organic/water mixtures. In mixed DMSO/water, it formed nanohelix. Due to the fluorescent nature of the naphthyl group, the nanohelix showed both CD and circularly polarized luminescence (CPL). When three achiral fluorescent molecules, pyrene-1-carboxylic acid (D2), rhodamine 110 (D3) and rhodamine B (D4), were incorporated into the helical structures formed by bola-1, the nanohelix could be remained and the CPL from the dye molecules could be induced. In addition, an energy transfer occurred between the bola-1 nanohelix and the dyes. By mixing the different emission dyes with the bola-1 in an appropriated ratio, a white CPL was obtained. It was found the dissymmetry factor of the white CPL could be increased through the energy transfer. This work provided a new convenient and efficient way of fabricating while CPL.
关键词： nanohelix,white CPL,circularly polarized luminescence,energy transfer,optical activity,Chiral nanostructures,bolaamphiphile
更新于2025-09-19 17:13:59
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Nanoplasmonics - Fundamentals and Applications || Magneto‐Plasmonics and Optical Activity in Graphene‐Based Nanowires
摘要： Nowadays, graphene plasmonics shows a great number of features unusual for traditional (metal-based) plasmonics from high localization and large propagation distance of surface plasmon-polaritons (SPPs) through the existence of both TE- and TM-polarized SPPs to the possibility of controlled SPPs by graphene chemical potential (or, equivalently, by gate voltage or chemical doping). Cylindrical graphene-based plasmonic structures have some advantages in contrast to planar geometry: absence of edge losses, existence of high-order azimuthal modes, etc. In this work, we discuss some ways to obtain an optical activity in cylindrical graphene-based plasmonic structures and its possible applications to SPPs manipulation.
关键词： surface plasmon-polaritons,metasurface,graphene,magneto-plasmonics,optical activity
更新于2025-09-16 10:30:52
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Reversible LED controlled optical activity of a cholesteric liquid crystal layer
摘要： A thin layer of the photosensitive cholesteric liquid crystal possessing a high value of the optical activity is studied. Reversible change in the optical activity controlled by two light emission diodes (LEDs) with different emission wavelengths is applied for information recording. The behavior of this structure under exposure to UV and blue light is investigated. A smooth decrease in optical activity caused by the UV light resulting in a change in the color of the structure between crossed polarizers is obtained. The reverse process occurs under exposure to the blue light. On the basis of the obtained results, two methods of optical information recording in such a layer have been demonstrated.
关键词： information recording,optical activity,cholesteric liquid crystals
更新于2025-09-12 10:27:22