We experimentally verified that a microplasma assembly can create a functional dielectric layer for the propagation of electromagnetic waves as a "plasma photonic crystal." A two-dimensional array in a square lattice was composed of columnar plasmas of about 2 mm in diameter, and the transmitted microwaves at 70-75 GHz showed a change of energy flow direction. This result is attributed to the fact that periodical structure is composed of individual plasma columns with a different dispersion than the ambient part and the experimental frequency range lies in the vicinity of the lowest band gap of the photonic crystal calculated theoretically.
Solvent-to-polymer chirality transfer was examined using
conjugated polymer with intramolecular stack structure (IaSS). When
achiral poly(diphenylacetylene)s (PDPAs) dissolved in limonene, the
solvent chirality was successfully transferred to the side phenyl
stack structure, leading to intramolecular axial chirality. The phenyl–phenyl
IaSS was under thermodynamic control to readily undergo asymmetric
changes in chiral limonene, leading to optical activity in the isotropic
structure between the main chain and resonant side phenyl rings. The
axial chirality was significantly affected by the chain length and
substitution position of the side alkyl groups. The longer alkyl chains
and bulkier alkyl group prevented direct intermolecular interactions
between the side phenyl rings and the chiral limonene molecules. PDPA
with sterically congested, highly stable, and regulated IaSS was not
favorable for efficient solvent-to-polymer chirality transfer.
Two theoretical approaches appropriate for two-dimensional plasma photonic crystals reveal dispersions of propagating waves including photonic ͑electromagnetic͒ band gaps and multiflatbands. A modified plane-wave expansion method yields dispersions of collisional periodical plasmas, and the complex-value solution of a wave equation by a finite difference method enables us to obtain dispersions with structure effects in an individual microplasma. Periodical plasma arrays form band gaps as well as normal photonic crystals, and multiflatbands are present below the electron plasma frequency in the transverse electric field mode. Electron elastic collisions lower the top frequency of the multiflatbands but have little effect on band gap properties. The spatial gradient of the local dielectric constant resulting from an electron density profile widens the frequency region of the multiflatbands, as demonstrated by the change of surface wave distributions. Propagation properties described in dispersions including band gaps and flatbands agree with experimental observations of microplasma arrays.
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