Optical chirality (OC) - one of the fundamental quantities of electromagnetic fields - corresponds to the instantaneous chirality of light. It has been utilized for exploring chiral light-matter interactions in linear optics, but has not yet been applied to nonlinear processes. Motivated to explore the role of OC in the generation of helically polarized high-order harmonics and attosecond pulses, we first separate the OC of transversal and paraxial beams to polarization and orbital terms. We find that the polarization-associated OC of attosecond pulses corresponds to that of the pump in the quasi-monochromatic case, but not in multi-chromatic pump cases. We associate this discrepancy to the fact that the polarization OC of multi-chromatic pumps vary rapidly in time along the optical cycle. Thus, we propose new quantities, non-instantaneous polarization-associated OC, and timescale-weighted polarization-associated OC, that link the chirality of multi-chromatic pumps and their generated attosecond pulses. The presented extension to OC theory should be useful for exploring various nonlinear chiral light-matter interactions. For example, it stimulates us to propose a tri-circular pump for generation of highly elliptical attosecond pulses with a tunable ellipticity.
Geometrical chirality is a property of objects that describes three-dimensional mirror-symmetry violation and therefore it requires a non-vanishing spatial extent. In contrary, optical chirality describes only the local handedness of electromagnetic fields and neglects the spatial geometrical structure of optical beams. In this manuscript, we put forward the physical significance of geometrical chirality of spatial structure of optical beams, which we term "Kelvin's chirality". Further, we report on an experiment revealing the coupling of Kelvin's chirality to optical chirality upon transmissi…
Analytical forms of the optical helicity and optical chirality of monochromatic Laguerre-Gaussian optical vortex beams are derived up to second order in the paraxial parameter $kw_0$. We show that input linearly polarised optical vortices which possess no optical chirality, helicity or spin densities can acquire them at the focal plane for values of a beam waist $w_0 \approx λ$ via an OAM-SAM conversion which is manifest through longitudinal (with respect to the direction of propagation) fields. We place the results into context with respect to the intrinsic and extrinsic nature of SAM and OAM…
Characterizing chirality is highly important for applications in the pharmaceutical industry, as well as in the study of dynamical chemical and biological systems. However, this task has remained challenging, especially due to the ongoing increasing complexity and size of the molecular structure of drugs and active compounds. In particular, large molecules with many active chirality centers are today ubiquitous, but remain difficult to structurally analyze due to their high number of stereoisomers. Here we theoretically explore the sensitivity of high harmonic generation (HHG) to the chirality…
A beat wave approach to harmonic generation in chiral media
STFC Rutherford Appleton Laboratory（英国科学和技术设施委员会拉瑟福德·阿普尔顿实验室）；University of Strathclyde（斯特拉斯克莱德大学）；Imperial College London（伦敦帝国学院）；Instituto de Ciencia de Materiales de Madrid (ICMM), Consejo Superior de Investigaciones Científicas (CSIC)（马德里材料科学研究所，西班牙高等科学研究委员会）
When circularly polarized light interacts with a nanostructure, the optical response depends on the geometry of the structure. If the nanostructure is chiral (i.e., it cannot be superimposed on its mirror image), then its optical response, both in near-field and far-field, depends on the handedness of the incident light. In contrast, achiral structures exhibit identical far-field responses for left- and right-circular polarization. Here, we show that a perfectly achiral nanostructure, a plasmonic metamolecule with trigonal D3h symmetry, exhibits a near-field response that is sensitive to the h…
Switching the Optical Chirality in Magneto-plasmonic Metasurfaces Using Applied Magnetic Fields
手性纳米光子器件在手性分子传感、偏振多样性纳米光子学和显示技术等方面具有广阔的应用前景。主动手性纳米光子器件是一种可以通过外界激励来控制光学手性的器件，引起了人们极大的研究兴趣。然而，光学手性的有效调制一直是具有挑战性的。在这里，我们展示了开关的非本征手性施加磁场的磁等离子体超颖表面设备的基础上的磁光氧化物材料，Ce 1 Y2 Fe 5 O 12（Ce：YIG）。由于Ce：YIG具有低的光损耗和强的磁光效应，在掠入射条件下，在波长为950 nm的激光器上施加-0.65° ~+1.9°范围内的磁场，实现了巨大且连续的远场圆二色性（CD）调制。远场CD调制是由于磁光圆二色性和施加的磁场对超手征场的近场调制。最后，我们在使用自组装制造的毫米级磁等离子体元表面中展示了磁场可调手征成像。我们的研究结果为实现平面集成的、大规模的、具有活性的手性超表面提供了一种新的途径。
Artificial nanostructures enable fine control of electromagnetic fields at the nanoscale, a possibility that has recently been extended to the interaction between polarised light and chiral matter. The theoretical description of such interactions, and its application to the design of optimised structures for chiroptical spectroscopies, brings new challenges to the common set of tools used in nano-optics. In particular, chiroptical effects often depend crucially on the relative orientation of the scatterer and the incident light, but many experiments are performed with randomly-oriented scatter…
Optical Control of Chirality by Ultrafast Symmetry Breaking in Membrane Metasurfaces
École Polytechnique Fédérale de Lausanne (EPFL)（洛桑联邦理工学院）；Shubnikov Institute of Crystallography, NRC “Kurchatov Institute”（库尔恰托夫国家研究中心舒比尼科夫晶体学研究所）；School of Physics and Engineering, ITMO University（ITMO大学物理与工程学院）；University of Brescia（布雷西亚大学）；Qingdao Innovation and Development Center, Harbin Engineering University（哈尔滨工程大学青岛创新发展基地）；Theoretical Physics and Quantum Technologies Department, National University of Science and Technology ‘MISIS’（莫斯科国立科学技术大学“MISIS”理论与量子技术系）
The realization of lossless metasurfaces with true chirality crucially requires the fabrication of three-dimensional structures, constraining their feasibility for experiments and hampering practical implementations. Even though the three-dimensional assembly of metallic nanostructures has been demonstrated previously, the resulting plasmonic resonances suffer from high intrinsic and radiative losses. The concept of photonic bound states in the continuum (BICs) is instrumental for tailoring radiative losses in diverse geometries, especially when implemented using lossless dielectrics, but appl…
