The properties of chiral photonic crystals with a pitch gradient were investigated both experimentally and theoretically. The liquid-crystalline cell was prepared by bringing two cholesteric liquid crystals (CLCs) with different pitches into contact. There are some essential features in the dynamics of diffusion between the two CLCs. The most important feature is the fact that establishing the final equilibrium pitch (for the temperatures below 17°C) takes a long time—roughly 3 months or more—which, in turn, allows us to investigate the nonstandard change in the reflection spectra during the diffusion. The two reflection curves do not directly actually get closer and merge into one peak, as usual, but the left one gradually gets smaller and almost vanishes, and the right one expands. For this reason, a theoretical model of a pitch change was developed and it was seen that this model does not coincide with the classical ideas of the pitch change. It was also assumed that due to the “freezing” effect during the diffusion process, one could have fixed the intermediate states of the pitch gradient.
We investigated the zone structure peculiarities and the photonic density of states (PDS) of the eigen polarizations (EPs) in the system composed of a stack of layers of a cholesteric liquid crystal (CLC) and an isotropic medium. The problem was solved by Ambartsumian’s layer addition modified method. The influence of the CLC sublayer thicknesses and the thicknesses of the isotropic media layers on the reflection an PDS spectra of the system is investigated.
The photonic densities of states (PDS) of the eigen polarizations (EPs) in a cholesteric liquid crystal (CLC) filled with the Fabry-Perot (FP) resonator are calculated. We obtained the dependences for the PDS on the FP resonator plates refractive indices. We showed, that the decrement and increment of the FP resonator plates refractive indices (started with the value, n = nm , where nm is the mean value of the CLC refractive index) lead to a sharp increase of the maximum PDS and, consequently, lead to a sharp decrement of the laser excitation threshold. The absorption and emission peculiarities of this system are investigated too. It is shown that the subject system can work as a low threshold laser.
The reflection and transmission of electromagnetic waves in 1D photonic crystals (PCs) is discussed. The periodicities of
both dielectric and magnetic permittivity are taken into account. The dielectric and magnetic permittivities are
considered as spatially changing arbitrary functions. We show that for a certain, sufficiently large, range of cases this
problem can be reduced to a set of two linear differential equations instead of complicated matrix equations of transfermatrix
method. The effects of the Photonic Band Gap (PBG) shift, width change, new transmission zone contacts, etc., in
cases of different PC apodization and chirp are investigated. This method works fine for standard PCs, as well as for left
media and metamaterials. An important consequence is the condition for PBG suppression for all wavelengths,
associated with non-constancy of both dielectric and magnetic permittivities.
We investigate light wave propagation through a one-axis anisotropic medium layer with simultaneously non-unit
dielectric and magnetic tensors. 4x4 - Δ▵(see manuscript) matrix is built. We consider the general case when the dielectric and magnetic
permittivity tensor elements have both positive and negative sings. We obtained the dispersion equation and then built
dispersion surfaces for a homogeneous anisotropic uniaxial material when the material is negative or positive (both with
respect to the wave vector and Pointing's vector orientation of the refracted wave; the sign of the material is accordingly
defined below.) Electromagnetic plane waves propagating inside the medium can exhibit dispersion surfaces in the form
of ellipsoids of revolution, hyperboloids of one sheet, or hyperboloids of two sheets. The conditions of negative
refraction with respect to the wave vector and Pointing's vector orientation are considered. We found wave nonreciprocity
for the oblique incidence on the considered system and we showed that such a system can work as an alloptical
diode.
A simple and effective method to measure an electromagnetic wave polarization plane's weak rotations in various media is proposed. The specific features of the polarization plane’s rotation amplification (PPRA) for the light reflection and transmission through the absorbing and amplifying anisotropic layers are calculated. The amplification effect for an isotropic and cholesteric liquid crystal (CLC) layers are also considered. In conclusion the question of probable choice of the amplifier's noise/signal ratio is discussed.
Some optical properties of the multilayer system: a helical periodical medium layer (1) (HPML(1))-an isotropic dielectric layer (IDL)-HPML(2) are discussed. HPML is in external magnetic field and due to this it becomes nonreciprocal. The electromagnetic wave energy distribution peculiarities inside the system are investigated as well. It is shown that wave energy accumulation takes place in certain spectral regions. Multilayer optical systems based on realistic materials with periodical structure are also discussed under the scope of applications for liquid or gas-heaters and for using as a solar energy and fiber optics converters.
The influence of an external magnetic field on to the magneto-optical properties of media with a helical periodical structure is discussed. The case of light normal incidence is considered, and it is assumed that the external magnetic field is directed along medium axis. The transmission and reflection of the light incident normal onto a thin film having helical structure and being in external magnetic field is discussed. It is shown that at certain conditions this system can work as an ideal optical diode or one-sided reflector for polarized light. It is shown that when absorption is present in the system it becomes nonreciprosity for non-polarized light, i.e. a new type of nonreciprocity is appeared.
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