Eigenmodes of a chiral sphere placed in a dielectric medium were investigated in details. Excitation of these eigenmodes by a plane wave and a chiral molecule radiation was studied both analytically and numerically. It was found that decay rates of "right" and "left" enantiomers are different in the presence of the chiral sphere. Strong dependence of radiation pattern of the chiral molecule placed in the vicinity of the chiral sphere on chirality strength was also demonstrated. An interesting correlation between chirality of sphere and spatial spirality (helicity, vorticity ...) of the electromagnetic fields in the presence of chiral sphere was observed for the first time.
IntroductionThe optical Tamm state, which can occur either on the boundary of two photonic crystals [1,2] or on the boundary of a photonic crystal and a metal film [3][4][5][6][7][8][9][10][11][12], has recently attracted attention of researchers in nano-optics community. The optical Tamm state in a system with a photonic crystal covered with a metal film is especially interesting because it allows one to combine its complicated physics with the rich physics of plasmon surface waves. Since the first experimental demonstration [3], the optical Tamm state is an object of numerous researches. In particular, interaction of the Tamm state and a surface plasmon wave has been already shown [4,5]. Besides, the scheme of a sensor which is sensitive to the change of a refractive index based on the optical Tamm state has been offered [6,7]. Recently, in a system consisting of a photonic crystal and a perforated metal film, effects of the extraordinary transmission of light and huge asymmetry of transmission related to the optical Tamm state have been discovered [8,9]. The optical Tamm state has been investigated in the presence of nonlinear effects, particularly as a lasing mode of the nanolaser [10], it has been used to enhance the second harmonic generation [11] and to control spontaneous radiation of quantum emitters [12].In this work, we investigate another effect associated with the optical Tamm state. The photonic crystal necessary to observe an optical Tamm resonance supports the propagation of a set of waveguide modes. In this paper, we show that it is possible to achieve an interaction between the waveguide modes of the photonic crystal and the Tamm state with the help of a periodic lattice of slits in a metal film. We show that this interaction results in the Fano resonance, which is a typical sign of the interaction of high-quality dark and lowquality bright modes. In spite of the fact that the research of Fano resonance in photonic and plasmonic structures is a hot topic now [13-18], we do not know any investigation devoted
AbstractOptical properties of the photonic crystal covered with a perforated metal film were investigated and the existence of the Fano-type resonances was shown. The Fano resonances originate from the interaction between the optical Tamm state and the waveguide modes of the photonic crystal. It manifests itself as a narrow dip in a broad peak in the transmission spectrum related to the optical Tamm state. The design of a sensor based on this Fano resonance that is sensitive to the change of the environment refractive index is suggested.
Two-dimensional lattices of chiral nanoholes in a plasmonic film with lattice constants being slightly larger than light wavelength are proposed for effective control of polarization and spatial properties of light beams. Effective polarization conversion and strong circular dichroism in non-zero diffraction orders in these chiral metafilms are demonstrated by electromagnetic simulations. These interesting effects are found to result from interplay between radiation pattern of single chiral nanohole and diffraction pattern of the planar lattice, and can be manipulated by varying wavelength and polarization of incoming light as well as period of metastructure and refractive indexes of substrate and overlayer. Therefore, this work offers a novel paradigm for developing planar chiral metafilm-based optical devices with controllable polarization state, spatial orientation and intensity of outgoing light.
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