Origin and manipulation of band gaps in three-dimensional dielectric helix structures

Abstract

In this study, we present a comprehensive analysis to examine the origin of circular polarization stop bands in a dielectric helix structure. We show that band gaps in a helix structure may result from Bragg resonance or non-Bragg mechanism. The two types of gaps exhibit distinct optical properties and display an opposite dependence with respect to structural periodicity. The interplay of gaps not only gives rise to various operation scenarios, but results in pronounced modifications to dispersion characteristics that lead to abnormal propagation properties of circularly polarized waves. Our findings reveal versatile behaviors of circularly polarized light interacted with a three-dimensional helix medium, which can be of great importance for the design and implementation of circular polarization-dependent devices and applications.

Scattering of plane-wave and twisted photons by helical media

“…As far as a nonperturbative analysis is concerned, we investigated scattering of photons by the plate made of helical medium invariant under translations in the (x, y) plane. Many properties of such scattering were already investigated in the literature [23,24,26,40,42,43,45,46,58]. Nevertheless, we established several new, to our knowledge, results.…”

“…Many optical properties of the media with permittivity tensor of such a form were considered in [23,24,26,40,[42][43][44][45][46]. In the particular case α = β and y = 0, this permittivity tensor describes the electromagnetic properties of C * -smectics, whose optical characteristics were studied in [16].…”

“…Notice that the initial photon state can be mixed. In that case, one should suppose that ρ in λ λ (k, k) is the momentum space diagonal of the density matrix of the initial photon state, and c in and ρ spin in are defined as in (46) and (47).…”

“…However, in the case k ⊥ = 0, the system (89) is exactly solvable. Such solutions were investigated in [23,24,26,40,42,43,45,46,58]. As for q-plates, the paraxial propagation of electromagnetic The asymmetry is positive in this case.…”

“…Notice also that the imaginary gap disappears for α = β and y = 0, i.e., in the case of C * -smectics and cholesterics, since a = c and the asymmetry vanishes in the case. Other non-Bragg band gaps in three dimensional dielectric helix structures were discussed in [46]. The real gap is a well-known forbidden band gap of the dispersion law of photons propagating in C * -smectics or cholesterics [14][15][16].…”