Two-beam coupling measurements of grating phase in a photorefractive polymer

Electric-field stabilization and competition of gratings in a photorefractive polymer

“…These photosensitivities are approximately 100 times those reported for BisA-4-nitro-1,2-phenylenediamine (NPDA):DEH' and 30 times larger than for polymethyl methacrylate-paranitroaniline:DEH. 3 The photosensitivity increased between with field ( Fig. 1), as was also observed in BisA-NPDA," 2 likely owing to field effects on the carrier photogeneration rate and mobility.…”

“…Similar grating competition, screening, and fixing phenomena associated with multiple traps have all been observed in inorganic photorefractive crystals," and evidence for grating competition in a photorefractive polymer has recently been reported. 3 The type A grating and the photoconductivity are associated with the NAT chromophores as was shown in BisA-NPDA:DEH." 2 We do not know the identity of the type B traps.…”

“…Promising new photorefractive polymers have been reported recently.`- 3 These hybrid materials combine the best available electro-optic polymers 4 with charge-transport agents and (potentially) photosensitizing dyes used in electrophotography and may replace photorefractive crystals 5 in future applications because of the relative low cost and flexibility of fabrication of polymers. It is necessary, however, to improve the performance of current photorefractive polymers.…”

Measurement of the photorefractive grating phase shift in a polymer by an ac phase-modulation technique

“…The electric field dependence of the photorefractive gain coefficient was accurately described by standard photorefractive theory. The phase-modulation technique provides improved accuracy in measurement of the photorefractive phase shift (compared with the commonly used sample translation technique 20 ) of Ϯ1°near phase shifts of 90°and Ϯ3°near phase shifts of 45°. From fits to the data we determined the limiting space-charge electric field of this polymer to be 41 Ϯ 3 kV/cm and the effective density of photorefractive traps to be 2.0 Ϯ 0.2 ϫ 10 15 cm Ϫ3 .…”

“…16,17 Monitoring the two-beam coupling signal when rapidly translating the grating (or the sample) can also be a method to measure the photorefractive phase shift. [18][19][20][21] In this paper we present results of the measurement of the photorefractive phase shift in the photorefractive polymer bisphenol A 4,4Ј-nitroaminostilbene (bisA-NAS) with 29 wt.% benzaldehyde diphenyl hydrazone 22 (DEH), using a modified ac phase-modulation technique based on the method introduced by Cudney et al …”