Hydrostatic pressure response of polymer-dispersed liquid crystal gratings

Abstract

Experimental analysis showed shifts in Bragg wavelength when examining the effects of applied hydrostatic pressure (0–10psi above ambient) on the reflection spectrum of holographic polymer-dispersed liquid-crystal Bragg gratings. With increased pressure, a spectral blueshift was observed, suggesting applications in optical pressure sensing. To analyze and quantify the observations, a Gaussian curve was fitted to the reflection spectrum of the gratings at each pressure interval. The spectral dependence on applied pressure is explained by elastic compression of the polymer sections of the Bragg planes in the reflection grating. The presented theory shows that the response of the gratings to the applied pressure is independent of the probe light incidence angle, but is linearly dependent on the ambient pressure reflection wavelength of the gratings.

Holographic Polymer‐Dispersed Liquid Crystals: Materials, Formation, and Applications

“…This shift was caused by the Poisson contraction of the polymer segments of the grating parallel to the grating vector as the film was stretched perpendicular to the grating vector. Fontecchio et al developed hydrostatic pressure sensors based on H-PDLC reflection gratings [139,141]. Figure 70 shows the testing schematic.…”

“…The configuration used to measure the reflected spectrum of the H-PDLC pressure sensors. Light is incident on the film at ∼30• to the sensor normal[141].…”

Monomer Functionality Effects in the Formation of Thiol−Ene Holographic Polymer Dispersed Liquid Crystals

“…The development of dynamic diffraction gratings through the formation of holographic polymer dispersed liquid crystals (HPDLCs) has shown great promise in a variety of applications such as displays, photonic components, lasing, electrooptic filters, and pressure sensors . Unfortunately, widespread use of acrylate-based HPDLC materials has been prevented by performance degradation and suboptimal performance .…”

“…The development of dynamic diffraction gratings through the formation of holographic polymer dispersed liquid crystals (HPDLCs) has shown great promise in a variety of applications such as displays, 1 photonic components, 2 lasing, 3 electrooptic filters, 4 and pressure sensors. 5 Unfortunately, widespread use of acrylate-based HPDLC materials has been prevented by performance degradation 6 and suboptimal performance. 7 Recently, thiol-ene-based HPDLCs have been demonstrated that overcome many of these limitations as they exhibit stable performance for over 3 years, 8 improved switching voltage (SV), improved baseline transmission, and increased overall diffraction efficiency (DE).…”

Tunable polymer/liquid crystal composite devices

“…Sensing Applications Based on H-PDLCSensing is another big potential application for H-PDLC gratings, especially for reflection mode. Fontecchio et al developed hydrostatic pressure sensors based on H-PDLC reflection gratings 90,91. With a special treatment, the reflective H-PDLCs can contain many air voids without any damage to the grating structures.…”