Diffraction and Polarization Properties of Electrically–Tunable Nematic Liquid Crystal Grating

Abstract

This work demonstrates an electrically-tunable nematic liquid crystal (NLC) diffraction grating with a periodic electrode structure, and discusses the polarization properties of its diffraction. The efficiency of the first-order diffraction can be gradually controlled by applying external electric fields cross the NLC, and the maximum diffraction efficiency of the first-order diffraction that can be obtained is around 12.5% under the applied voltage of 5.0 V. In addition to the applied electric field, the efficiency of the first-order diffraction can also vary by changing the polarized state of the incident beam. Antisymmetric polarization states with symmetrical intensities in the diffractions corresponding to the +1 and −1 order diffraction signals are also demonstrated.

Liquid Crystal Devices for Beam Steering Applications

“…An early example of such was performed using simple interdigitated electrodes (IDEs) to create a diffraction grating by Lindquist et al in 1994 [138] (see Figure 11). The maximum observed efficiencies of m = 1 order for this device and other similar ones were found to be around 30% [138][139][140][141], which is comparable to the 38% theoretical limit of a sinusoidal phase grating. Similarly, diffractive microlens arrays have been fabricated with periodically hole-patterned electrodes [142,143].…”

Electrically Tuneable Optical Diffraction Gratings Based on a Polymer Scaffold Filled with a Nematic Liquid Crystal

“…Tunability is one of the important properties of diffraction gratings. Various tuning methods have been proposed; diffractive properties can be modulated by an applied electrical voltage [ 25 , 26 , 27 , 28 ], magnetic field [ 29 , 30 , 31 ], pressure, temperature, or by another electromagnetic wave [ 32 , 33 , 34 , 35 , 36 , 37 ]. Liquid crystals (LCs) are very suitable for the construction of tuneable optical diffraction gratings [ 38 , 39 ] since they possess a unique combination of mechanical softness and strong optical anisotropy that provides relatively easy control of LC molecules’ orientation.…”

“…Liquid crystals (LCs) are very suitable for the construction of tuneable optical diffraction gratings [ 38 , 39 ] since they possess a unique combination of mechanical softness and strong optical anisotropy that provides relatively easy control of LC molecules’ orientation. Due to the strong sensitivity of LCs to various external stimuli, it is possible to generate periodic structures built from LCs with periodically modulated stimuli, for instance, by using periodic electrode configurations [ 28 , 40 ] or via periodic alignment layers. The latter can be achieved either by rubbing [ 41 , 42 ] or by photo-alignment [ 43 , 44 ].…”

Switchable Diffraction Gratings Based on the Periodic Binary Alignment of a Nematic Liquid Crystal

“…Switchable diffraction LC gratings are used successfully as optical elements for spatial switching, multiplexing, and transforming the polarization of light beams [8][9][10][11]. The principle of generating such structures is based on creating a locally inhomogeneous (multidomain) distribution of LCs on a current-conducting surface.…”