Light-addressable liquid crystal polymer dispersed liquid crystal

Luciano De Sio,Elena Ouskova,Pamela Lloyd,Timothy J Bunning,Nelson Tabiryan,Rafael Vergara

doi:10.1364/ome.7.001581

Abstract

Scattering-free liquid crystal polymer-dispersed liquid crystal polymer (LCPDLC) films are fabricated by combining a room temperature polymerizable liquid crystal (LC) monomer with a mesogenic photosensitive LC. The morphological and photosensitive properties of the system are analysed with polarized optical microscopy and high resolution scanning and transmission electron microscopy. A two-phase morphology comprised of oriented fibril-like polymeric structures interwoven with nanoscale domains of phase separated LC exists. The nanoscale of the structures enables an absence of scattering which allows imaging through the LCPDLC sample without optical distortion. The use of a mesogenic monomer enables much smaller phase separated domains as compared to non-mesogenic systems. All-optical experiments show that the transmitted intensity, measured through parallel polarizers, can be modulated by the low power density radiation (31 mW/cm2) of a suitable wavelength (532 nm). The reversible and repeatable transmission change is due to the photoinduced trans-cis photoisomerization process. The birefringence variation (0.01) obtained by optically pumping the LCPDLC films allow their use as an all-optical phase modulator.

Highlights

Photosensitive materials have been extensively studied in the last few years due to their ability to change mechanical, electrical and optical properties under the influence of light [1,2,3]
We demonstrate here that a liquid crystal polymer-dispersed liquid crystal polymer (LCPDLC) system possessing a low molar mass photosensitive liquid crystal (LC) can be utilized as a scattering-free optically controlled phase modulator
The photosensitive properties of the LCPDLC characterized by a pump-probe setup are promising for controlling the transmitted light intensity and phase with a relatively low pump beam power density

Summary

Introduction

Photosensitive materials have been extensively studied in the last few years due to their ability to change mechanical, electrical and optical properties under the influence of light [1,2,3]. The end result is a thin film ‘nanocomposite’ with small irregularly shaped inclusions of LC which are phase separated from a mesogenic matrix Advantages to this system include the ability to induce alignment in both the low molar mass LC and the mesogenic monomer (before polymerization), fabrication of complex curved shapes due to the ‘liquid’ nature of the precursor, and better index matching of the two phases (enabling truly transparent nanocomposites). These are highly promising for applications in systems where fast phase modulation of an optical signal is needed. We demonstrate here that a LCPDLC system possessing a low molar mass photosensitive LC can be utilized as a scattering-free optically controlled phase modulator

Objectives

Results

Conclusion