Fine tuning of glass transition temperature in monolithic organic photorefractive material

• Published in: Optical materials Vol. 21; no. 1; pp. 359 - 364
• Main Authors: Hwang, Jaehoon, Seo, Jangwon, Sohn, Jiwon, Park, Soo Young
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Amsterdam Elsevier B.V 2003; Elsevier Science
• Subjects: Exact sciences and technology; Fundamental areas of phenomenology (including applications); Glass transition temperature; Monolithic chromophore; Optical materials; Optics; Other nonlinear optical materials; photorefractive and semiconductor materials; Photorefractive; Physics; Polymers and organics; 42.70.N; Photorefractive; Monolithic chromophore; Glass transition temperature; Organic glass; Transition temperature; Organic polymers; Experimental study; Benzoxazole derivative polymer; Glass transition; Two wave mixing; Composite materials; Photorefractive materials; Optical properties; Carbazole derivative polymer; Chemical composition; Optical materials; Nonlinear optics
• ISSN: 0925-3467; 1873-1252
• DOI: 10.1016/S0925-3467(02)00165-9

In order to study the effect of T g on the photorefractivity in organic monolithic system, we designed and synthesized photorefractive homopolymer (PCzBO) and organic glass (EHCzBO), consisting of the same monolithic chromophore. Photorefractive polymer composites were prepared by blending them. T g of PCzBO and EHCzBO were 106 and 29 °C, respectively. T g of polymer composite could be controlled precisely by the compositional ratio of PCzBO and EHCzBO in the range from 29 to 40 °C. Since both the polymer and the organic glass contained the same chromophore structure, all the samples had nearly the same chromophore concentration even though compositional ratios of them were different, as was confirmed by UV–visible spectroscopy. Frequency-dependent ellipsometric technique showed that the birefringence contribution through the orientation enhancement effect was dominant in the refractive index modulation of our low T g composites. It was found that the reorientation of chromophore according to the modulated voltage was more limited for the higher T g composite, which consequently reduced the birefringence contribution. The diffraction efficiency and two beam coupling coefficient were decreased with the increase of T g.