Theoretical approach of a polymer stabilized blue phase beam steering

Abstract

Abstract-Nematic liquid crystal (LC)-based beam steering has beenreported for wide applications. However, for conventional nematic LC beam steering the thickness is of several microns in order to have a wider deflection angle. The response time is relatively slow and the diffraction efficiency is low. In this work, novel beam steering based on polymer stabilized blue phase liquid crystal (PS-BPLC) has been designed and theoretically analyzed. This special mesophase of the chiral doped nematic LC has several advantageous characteristics, for example no need for alignment layers, microsecond response time and an isotropic voltage-off state. The results reveal control over phase retardation. The direction of the steered beam can be tuned by voltage. Depending on voltage configuration, either diffractive beam steering (0.5º deviation for 1st order) or a tunable continuous phase (tunable deviation of 0.002º) can be obtained. In the first case, the deflection angle could be tuned by stacks of samples. The second option has the same phase shift for the TE and TM modes so unpolarized light could be used.Over the last decade, nematic liquid crystal (LC)-based phase modulators have been reported for wide applications. Some interesting proposals have produced different optical elements as tunable lenses, optical vortices, etc. One of the phase modulators with more practical applications is the LC beam steering. The spatial distributed phase shift produced in these kind of devices cause deviations in the light direction passing through them. These systems have demonstrated several advantages as light-weight, low-voltage and low cost manufacture. Moreover, complete tunability without any need of moving parts is one of the most important features. Some important applications are laser and free space communications [1][2][3]. To achieve this function, different proposals based on nematic LC have been made in recent years [4][5][6]. Despite this, for conventional nematic LC beam steering, the thickness is of several microns in order to have a wider deflection angle. The response time is relatively slow and the diffraction efficiency is low. In this work, novel beam steering based on polymer stabilized blue phase liquid crystal (PS-BPLC) has been designed and theoretically analyzed. Polymer stabilized blue phase LC is a special mesophase of the chiral doped * E-mail: jalgorri@ing.uc3m.es nematic LC with several advantageous characteristics. For example, the molecular structure gives it four important features: a microsecond response time (approximately ten times faster than NLC), optical isotropic voltage-off state due to the three-dimensional lattice structure, multidomain voltage-on state structure and no need of alignment layers due to the self-assembly of these structures [7]. A novel structure having PS-BPLC and high resistivity layers is proposed. Earlier works have demonstrated the use of a high resistivity layer (modal control) for designing LC lenses [8] and microlenses [9], micro-axicon arrays [10], arrays of optical e...