arXiv subjects

Wei Lee

Publications and source records attributed to Wei Lee.

3 recordsLinked to original sources

arXiv2018

Chiral Optical Tamm States at the Interface between a Cholesteric and an All-Dielectric Polarization-Preserving Anisotropic Mirror

The chiral optical Tamm state is a new localized state of light at the interface between a polarization-preserving anisotropic mirror and an optically chiral medium such as a cholesteric liquid crystal. In this study the metal-free polarization-preserving mirror is used for efficient resonance control. We stress the advantage of the all-dielectric structure in obtaining high Q factor. The light is localized near the interface and the field decreases exponentially with the distance from the interface. The penetration of the field into the chiral medium is virtually blocked at wavelengths corresponding to the photonic band gap and close to the pitch of the helix. The polarization-preserving mirror has another photonic band gap as well. Our analytics agrees well with precise calculations, enabling intelligent design for laser and sensing applications.

physics.optics↗

arXiv2017

Chiral Optical Tamm States: Temporal Coupled-Mode Theory

The chiral optical Tamm state (COTS) is a special localized state at the interface of a handedness-preserving mirror and a structurally chiral medium such as a cholesteric liquid crystal or a chiral sculptured thin film. The spectral behavior of COTS, observed as reflection resonances, is described by the temporal coupled-mode theory. Mode coupling is different for two circular light polarizations because COTS has a helix structure replicating that of the cholesteric. The mode coupling for co-handed circularly polarized light exponentially attenuates with the cholesteric layer thickness since the COTS frequency falls into the stop band. Cross-handed circularly polarized light freely goes through the cholesteric layer and can excite COTS when reflected from the handedness-preserving mirror. The coupling in this case is proportional to anisotropy of the cholesteric and theoretically it is only anisotropy of magnetic permittivity that can ultimately cancel this coupling. These two couplings being equal results in a polarization crossover (the Kopp--Genack effect) for which a linear polarization is optimal to excite COTS. The corresponding cholesteric thickness and scattering matrix for COTS are generally described by simple expressions.

physics.optics↗

arXiv2011

Voltage-induced defect mode interaction in a one-dimensional photonic crystal with a twisted-nematic defect layer

Defect modes are investigated in a band gap of an electrically tunable one-dimensional photonic crystal infiltrated with a twisted-nematic liquid crystal (1D PC/TN). Their frequency shift and interference under applied voltage are studied both experimentally and theoretically. We deal with the case where the defect layer thickness is much larger than the wavelength (Mauguin condition). It is shown theoretically that the defect modes could have a complex structure with the elliptic polarization. Two series of polarized modes interact with each other and exhibit an avoided crossing phenomenon in the case of opposite parity.

physics.optics↗