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Tunable optical properties of liquid crystals through coupling of magnetic fields with director angles

GIRIJESH NARAYAN PANDEY1,* , NARENDRA KUMAR2, PAWAN SINGH3, KHEM B. THAPA3, ANIL KUMAR SHUKLA4

Affiliation

  1. Department of Applied Physics, Amity Institute of Applied Science, Amity University, Uttar Pradesh, Noida 201303, UP, India
  2. Department of Physics, SLAS, Mody University of Science and Technology, Lakshmangarh 332311, Sikar, Rajasthan, India
  3. Department of Physics, School of Physical and Decision Science, Babasaheb Bhimrao Ambedkar University (A Central University), Lucknow226025, UP, India
  4. Department of E &T, Amity School of Engineering and Technology, Amity University, Uttar Pradesh, Noida 20313, India

Abstract

In this research article, we show that the coupling of magnetic field with director angle of molecules can tune the optical properties of liquid crystal cell. Depending upon the strength of applied magnetic field, the liquid crystal exhibits phase transition including the twist bending phenomena having rotational order parameter that converts into isotropic phase. The interaction of magnetic field and directional angle is based on the boundary conditions and approximations leading to variation of the strength of coupling. First, while analyzing the optical characteristics, we find that the orientation angle increases with increase in the layer thickness of liquid crystal and decreases after reaching critical thickness of 50 nm, in which the variation is found only when the ratio H /HF is greater than 1 under increasing field, while in decreasing field similar variation is also found for the H/ HF ratio less than 1. Furthermore, on the basis of the transmission characteristics of asymmetric PC with liquid crystal defect, we note that, it offers the characteristics of multichannel filter in the central region of wavelength 6000 Ǻ, while the transmission is nearly 0.7 to 0.8. Depending on the twist bend phenomena inside liquid crystal cell, it can be employed in bistable and all-optical switching devices, and optical multichannel filters can be designed.

Keywords

Liquid crystals (LCs), Magnetic fields, Freedericksz transition field (HF), Order parameter, Phase transitions, Tunable optical properties.

Citation

GIRIJESH NARAYAN PANDEY, NARENDRA KUMAR, PAWAN SINGH, KHEM B. THAPA, ANIL KUMAR SHUKLA, Tunable optical properties of liquid crystals through coupling of magnetic fields with director angles, Optoelectronics and Advanced Materials - Rapid Communications, 16, 11-12, November-December 2022, pp.501-504 (2022).

Submitted at: May 19, 2022

Accepted at: Dec. 5, 2022