Space charge field and dynamics of the grating formation in a photorefractive polymer-dispersed liquid crystal based on a photoconducting polysiloxane

Abstract

A photorefractive system composed of liquid crystal droplets dispersed in a photoconducting polymer is characterized by means of two-beam coupling. The amplitudes and phases of the spatial variations of the refractive index and the absorption coefficient are measured using the moving grating technique. Dynamic measurements indicate that the phase of the refractive index modulation is nearly constant while the amplitude increases gradually. The maximum value of the internal space charge field can be estimated from the amplitude of the phase grating and is found to be of the order of one-hundredth of the external bias field.

Optimization of Photorefractivity Based on Poly(N‐vinylcarbazole) Composites: An Approach from the Perspectives of Chemistry and Physics

“…PR devices are used for holographic display applications: 1) high diffraction efficiency (>50%); 2) fast response time (<30 ms); 3) high dynamic range (for full color); 4) low absorption cross‐section at the recording wavelength; 5) long‐life operation (at least a few years); 6) simple process; 7) no scattering; and 8) low‐cost fabrication. To address issues 1 and 2, developers have recently been using several types of photoconductive polymers mainly in PR devices, including poly( N ‐vinylcarbazole) (PVCz),6–8 poly(acrylic tetraphenyldiaminobiphenyl) (PATPD),9, 10 polysiloxanes (PSX),11, 12 poly( p ‐phenylenevinylene) (PPV)13, 14 and so forth. In addition, highly‐functionalized monolithic materials have attracted much attention because of their stable PR properties 15, 16.…”

Optoelectronic and photonic properties of liquid crystals: electroluminescence and photorefractivity

“…The phase of ϕ n ≈ 90° indicates that charge carriers are trapped in the regions of the sample that are dark due to destructive interference of the incident light beams. A more detailed analysis and a model for estimating the size of the space charge field E sc will be presented in a forthcoming paper [25]. …”

Influence of doping on the photorefractive properties of a polymer-dispersed liquid crystal

“…The investigated PDLC samples ͑prepared as described previously 17,18 ͒ consist of the photoconductive matrix poly͓methyl-3-͑9-carbazolyl͒-propyl͒siloxan͔ ͑PSX3͒, fullerene C 60 ͑Fluka͒ as the photosensitizer, and the nematic liquid crystal mixture TL202 ͑Merck, Darmstadt͒. The investigated PDLC samples ͑prepared as described previously 17,18 ͒ consist of the photoconductive matrix poly͓methyl-3-͑9-carbazolyl͒-propyl͒siloxan͔ ͑PSX3͒, fullerene C 60 ͑Fluka͒ as the photosensitizer, and the nematic liquid crystal mixture TL202 ͑Merck, Darmstadt͒.…”