Analytical Study Of Light And Liquid Crystals Reorientation In Anistropic Photonic Crystals Using One-Dimension Finite Difference Time Domain (FDTD) Method

Najmiah Radiah, Mohamad (2013) Analytical Study Of Light And Liquid Crystals Reorientation In Anistropic Photonic Crystals Using One-Dimension Finite Difference Time Domain (FDTD) Method. Project Report. UTeM, Melaka, Malaysia. (Submitted)

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Abstract

This study demonstrate diffractive light from an anisotropic photonic crystal (PCs) based on holographic polymer-dispersed liquid crystals (HPDLCs) that are fabricated using two-beam interference with various pitch and exposure energy. One of the most powerful approaches for the analysis of PCs structure is 2×2 Jones method, which is widely used for most simple cases. But, in case of anisotropic structures which more microscopically or complex, it cannot analyze with accuracy in this method. In this research, we have studied and analyzed the modulation of light and liquid crystal reorientation in one-dimension anisotropic PCs from HPDLCs using FDTD method. HPDLCs is modeling as a mixture of polymer and liquid crystals (LCs) that categorized as an anisotropic medium. FDTD method is directly solve Maxwell’s equation with less approximation, so this method can analyze more flexible and general approach for the arbitrary anisotropic media. As the results from FDTD simulation, Bragg diffraction is occurred when Q>10 and highest diffraction efficiency occurred at ±19 degrees (Bragg angle) when incident beam is p polarization. Therefore, we can assumed the liquid crystal is aligned parallel to the grating constant vector (n // k) from perpendicular alignment (n  k) at low exposure energy or wider pitch grating. Furthermore, by using FDTD method, PCs model with no alignment of different sizes liquid crystal droplets that become smaller to the thickness direction or assumed as polymer are agreed with experimental results. Moreover, we can understand that the trend of diffraction efficiency become wider if the thickness of liquid crystal droplet is shorter.

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