Analysis of holographic polymer-dispersed liquid crystals (HPDLCs) for tunable low frequency diffractive optical elements recording

Abstract

Holographic polymer dispersed liquid crystals (HPDLCs) are the result of the optimization of the photopolymer fabrication techniques. They are made by recording in a photopolymerization induced phase separation process (PIPS) in which the liquid crystal molecules diffuse to dark zones in the diffraction grating originated. Thanks to the addition of liquid crystal molecules to the composition, this material has a dynamic behavior by reorientation of the liquid crystal molecules applying an electrical field. In this sense, it is possible to use this material to make dynamic devices. In this work, we study the behavior of this material working in low frequencies with different spatial periods of blazed gratings, a sharp profile whose recording is possible thanks to the addition of a Holoeye LCoS-Pluto spatial light modulator with a resolution of 1920x1080 pixels (HD) and a pixel size of 8 x 8 µm 2 . This device allows us to have an accurate and dynamic control of the phase and amplitude of the recording beam.

Diffractive and Interferometric Characterization of Nanostructured Photopolymer for Sharp Diffractive Optical Elements Recording

“…The analysis of the recording of blazed gratings in PVA/AA, Biophotopol and HPDLC materials [ 13 , 24 ] was carried out in previous research. Blazed grating is a complex DOE, which presents a sharp profile with abrupt changes.…”

“…In previous work [ 13 ], we explored the electro-optic capabilities of a holographic polymer dispersed liquid crystal (HPDLC) in working with low spatial frequencies.…”

“…Recently, Bowman et al proposed thiol-X click chemistry, with simple processability and environmental friendliness [ 18 ], and a 1,3-bis(phenylthio)-2-propyl acrylate (BPTPA) monomer, a writing monomer capable of reaching a refractive index modulation up to 0.029 [ 19 ]. In this work, we carry out a novel analysis of the recording dynamics of thiol-ene-based NPC gratings at low spatial frequencies, for which we follow the same procedure as those previously used for other families of photopolymers, such as polyvinyl alcohol acrylamide (PVA/AA) based photopolymers, one of the most widely-studied photopolymers due to its good characteristics [ 20 , 21 , 22 ], Biophotopol [ 22 , 23 ], or HPDLC [ 13 , 22 ]. PVA/AA and Biophotopol materials have also demonstrated good results working with complex DOEs, obtaining good results from the material and high diffraction efficiencies (DEs).…”

Application of Photopolymer Materials in Holographic Technologies

“…The great interest in using photopolymer materials in holographic technologies is determined by a number of advantages relative to other holographic materials, such as silver halide materials, dichromated gelatin (DCG), and photorefractive glasses, associated with their relatively low cost and simplicity of the processes for elements fabrication that are formed as a result of polymerization under light exposure without laborious preliminary or subsequent processing. Applied to holographic technologies, the most widely considered in the literature are photopolymerizable acrylamide (AA/PVA) compositions [1,2], compositions with the introduction of various additives to obtain new properties, including liquid crystals [3,4] and inorganic nanoparticles [5][6][7], materials with a diffusion recording mechanism (PQ/PMMA) [8,9]. The processes in materials, their properties, as well as the properties of holographic elements for various practical applications, including data storage [10,11], sensors [12], protective elements [13], and elements of holographic solar concentrators [14,15] are studied.…”

Design of a Liquid-Crystal-Tunable Terahertz Demultiplexer Based on a Metal-Insulator-Metal Waveguide

“…In recent years, nematic liquid crystals (NLCs) have been widely used in tunable optic-electric devices, because the optical axis of NLC molecules can be controlled by an external electric field or a magnetic field. The NLC's controllable dielectric properties, wide range of operating frequencies and multiple ways of being adjusted are attractive for design tunable devices [14,15]. In the gigahertz band, LC has been tailored in a filter or amplifier to adjust their operating bands [16,17].…”