Photo-alignment of liquid crystals in micro capillaries with point-by-point irradiation

A photo-alignment method for micro capillaries based on the SD-1 azo-dye is demonstrated. In this work a liquid-crystal molecules aligning layer is created by point-by-point irradiation of the azo-dye film by using an UV laser light. The method opens up new possibilities for an improved molecules' orientation control in both glass- and polymer-based photonic liquid crystal fibres. © 2014 Versita Warsaw and Springer-Verlag Wien

Periodic alignment of liquid crystal molecules in silica micro-capillaries

The direction of liquid crystal (LC) arrangement can be changed by different techniques. Photo-alignment method appears to be potentially the best technique to use in the case of micro-capillaries. Developing the photo-alignment method of liquid crystal molecules in silica micro-capillaries allowed to work on obtaining periodic orientation. The usage of amplitude masks in the irradiation allows to obtain a periodic alignment of molecules variable within a single sample. In this paper, the experimental results of the periodic orientations achieved are presented

Numerical Simulations of Electrically Induced Birefringence in Photonic Liquid Crystal Fibers

It has been recently experimentally demonstrated that propagation and polarization properties of the photonic liquid crystal fibers can be effectively tuned with the electric field. In particular, effective electric tuning of the phase birefringence has been obtained in the photonic liquid crystal fibers based on the high index glasses. Accurate numerical simulations of the impact of electric field on the guiding properties of the photonic liquid crystal fibers require complex methods, in which all important physical properties of the liquid crystal are taken into account (optical anisotropy, molecular orientation and relatively high losses). In this paper we present two different numerical approaches based on the finite element method. First one utilizes the simplified assumption of the "collective tilt" of molecules, and gives rough estimation of the phase birefringence tuning range. The second approach is much more rigorous, since electrically induced reorientation of the liquid crystal is calculated with a Q-tensor method giving the values of the inhomogeneous permittivity tensor. The value of the electrically induced birefringence calculated with the second method is in a good agreement with the experimental results

Hybrid photonic crystal fiber for highly sensitive temperature measurement

A hybrid photonic crystal fiber (PCF) is proposed and demonstrated for highly sensitive temperature measurement. The hybrid PCF is formed by selectively infiltrating liquid crystal 5CB into the first ring of air holes around one silica core of a twin-core PCF (TCPCF). In the modified TCPCF, one silica core guides light with a total internal reflection (TIR) mechanism, while the other silica core guides light through a photonic bandgap (PBG) mechanism, due to the infiltration of high refractive index 5CB. The co-existing of TIR and PBG waveguiding mechanisms in the TCPCF leads to a hybrid light guiding mechanism PCF, i.e. hybrid PCF. Theoretical analysis reveals that the TIR-guided core mode, PBG-guided core modes and 5CB channel modes in the hybrid PCF can concurrently propagate and interfere with each other, which is further verified by experimental results. Besides, experimental investigation on the temperature response of the hybrid PCF shows that the temperature sensitivities can be up to 4.91 nm °C−1 for nematic phase of 5CB, and −3.68 nm °C−1 for isotropic phase of 5CB, respectively. The proposed hybrid PCF is promising for applications of temperature-tunable optical filtering in optical fiber communication, sensing and laser systems.NRF (Natl Research Foundation, S’pore)MOE (Min. of Education, S’pore