Abstract
We report on theoretical and experimental investigations of optical wave propagations in two-dimensional photonic lattice structures formed in a holographic polymer-dispersed liquid crystal (HPDLC) film. In the theoretical analysis we employed the 2 × 2 matrix formulation and the statistical thermodynamics model to analyze the formation of anisotropic photonic lattice structures by holographic polymerization. The influence of multiple reflections inside an HPDLC film on the formed refractive index distribution was taken into account in the analysis. In the experiment we fabricated two-dimensional photonic lattice structures in an HPDLC film under three-beam interference holographic polymerization and performed optical measurements of spectral transmittances and wavelength dispersion. We also demonstrated the electrical control capability of the fabricated photonic lattice structure and its dependence on incident wave polarization. These measured results were compared with the calculated ones by means of photonic band and beam propagation calculations.
Highlights
Electro-optic photopolymer-liquid crystal (LC) composites known as holographic polymer-dispersed liquid crystals (HPDLCs) consist of LCs doped into photopolymer followed by holographic polymerization that represents a fast and relatively simple way of fabricating Bragg grating structures [1,2,3,4]
We examined the morphology of holographically patterned photonic crystals (PhCs) structures in HPDLC films by removing LC compound from PhC lattice sites
This was done by dipping cured HPDLC films into methanol and by observing the polymer structures in various cross sectional planes by means of a scanning electron microscopy (SEM)
Summary
Electro-optic photopolymer-liquid crystal (LC) composites known as holographic polymer-dispersed liquid crystals (HPDLCs) consist of LCs doped into photopolymer followed by holographic polymerization that represents a fast and relatively simple way of fabricating Bragg grating structures [1,2,3,4]. A different type of HPDLCs, polymer liquid-crystal polymer slices (POLICRYPS) or polymer liquid crystal polymer holograms electrically manageable (POLIPHEM) structures that can be fabricated above the LC nematic-isotropic transition temperature, has been developed [10,11] Because of their low light scattering properties as compared with HPDLCs possessing LC droplets they have been used for various photonic applications [12,13,14]. Possessing dielectric periodic structures in 2D and 3D space have been of great interest since they exhibit photonic band gaps (PBGs) in the optical spectrum Such PBGs provide the strong control of light propagation in such a way that optical waves at certain wavelengths are either inhibited or confined in PhCs. The fabrication of PhCs using inorganic materials has already reached a mature state of evolution [17,19,20,21,22]. Experimental results of strong polarization-dependent spectral transmittances and wavelength-dependent refraction as well as their electrical control are presented and are compared with the theoretical calculation
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