Shrinkage measurement for holographic recording materials

Abstract

There is an increasing demand for new holographic recording materials. One of them are photopolymers, which are becoming a classic media in this field. Their versatility is well known and new possibilities are being created by including new components, such as nanoparticles or dispersed liquid crystal molecules in classical formulations, making them interesting for additional applications in which the thin film preparation and the structural modification have a fundamental importance. Prior to obtaining a wide commercialization of displays based on photopolymers, one of the key aspects is to achieve a complete characterization of them. In this sense, one of the main parameters to estimate and control is the shrinkage of these materials. The volume variations change the angular response of the hologram in two aspects, the angular selectivity and the maximum diffraction efficiency. One criteria for the recording material to be used in a holographic data storage application is the shrinkage, maximum of 0.5%. Along this work, we compare two different methods to measure the holographic recording material shrinkage. The first one is measuring the angle of propagation for both diffracted orders ±1 when slanted gratings are recorded, so that an accurate value of the grating vector can be calculated. The second one is based on interference measurements at zero spatial frequency limit. We calculate the shrinkage for three different photopolymers: a polyvinyl alcohol acrylamide (PVA/AA) based photopolymer, one of the greenest photopolymers whose patent belongs to the Alicante University called Biophotopol and on the last place a holographic-dispersed liquid crystal photopolymer (H-PDLC)..

Nonlinear Correction Method for Si Photodiode Detectors and Its Application to the Electro-Optical Measurement for the PDLC Film

“…Besides, the electro-optic effect parameters T0, Tsat, Vth, and Vsat are independent of the incident light power. The light power meter can be directly used as a photodetector to measure the electro-optical effect of the PDLC to exclude the non-linear effect of the Si photodiode detector [21,22]. However, when measuring the optical response of the PDLC, the delay time of the light power meter is more than the Si photodiode detector.…”