No abstract

No abstract

No abstract

For the performance of the PR effect, materials must exhibit the photoconductivity (PC) and the linear electrooptic response (EO) simultaneously [l]. To supply the PC property in PR composites, the photosensitive molecule and the transport agent are necessary. Up to now, several photosensitizers have been used such as TNF[2], c60[3,4], BDK[5], TCNQ[6], PDCI[6], TPY and others. As early as in 1992, Wang has suggested that C~O is a excellent hole generator for a polymeric photoconductor, especially doped in PVK [PVK stands for poly(Nvinylcarbazole)][7]. Almost at the same time, Zhang et a1.[3] and Silence et a1.[4] used it as the PR potosensitizer in different composites, in which they both implied that c 6 0 is an excellent PR photosensitizer.The photogeneration quantum efficiency (PGQE) 4 is an important parameter in photocoriductivity property of a material, which has been regarded to follow Onsager model [8] or Braun modified Onsager model [9]. However, because of the assumptions in Ref. 9 including i) 4 is independent of the illumination intensity and ii) the mobility p is temperatureindependent, the latter is also not a perfect model.In ithis paper, we presented the experimental demonstration of the PGQE in the composite of C60:P'VTK. 4 mg c 6 0 was dissolved in 2 ml chlorobezene, then 90mg PVK was added in the filtered solution while stirred and heated. The solution was spin coated onto indium-tin-oxide (ITO) covered slide with a set of circular silver electrodes vacuum deposited on the top of the polymer film. The film thickness was measured to be -4.25 pm, dielectric constant 2.43 at 1 SKHz, and glass transition temperature (T,) in the scale of 80-90 'C.The studies of the PGQE was carried out via the photoconductivity by measuring the photocurrent through the sample as used in Ref. 10. Applied field dependence of the PGQE in C60:PVK system with a weight ratio 4:90 was carried out at room temperature (20 "C) with the illuminalion intensity of 5 mW/cm2. The applied field varied from 50 V to lOOV between the IT0 and silver electrodes ( with a distance of 4.25 pm). Experimental data were fitted by both Onsager model as shown in Fig. 1, the values of &=0.9 and q~1 . 6 2 5 nm were estimated, which wlxe in excellent agreement with &=0.91 and ro=1.6 nm obtained by Wamg [7].The intensity-dependence was demonstrated at an applied field of 12 MV/m at 20 "C, and the result was represented in Fig. 2. Two different behaviors were exhibited in different intensity levels. At extent of weak illumination intensity, (1<10=1 3mW/cm2), q4 behaved intensity independently with a value of -2 . 5~ 1 0-4. For P>lo=l 3mW/cm2, a decrease appeared along with the increasing of the illumination intensity, which could be fitted in form of a sublinear variation of &&llIc. The solid line in Fig. 3 was calculated with qb"=4.9~10-~ and <=0.28. Tamura et al. reported also the decreasing trend, but they did not mention the phenomenon of intensity-independence [ 1 11.In both Onsager theory [8] and Braun theory [9,12], the intensity-independ...

A new method of one-step rainbow holography of diffuse three-dimensional objects with no slit is proposed. Diffuse three-dimensional objects are translated uniformly along the direction of the y(0) axis. A coherent plane wave illuminates the objects and its propagation direction is situated on the x(0)-z(0) plane. As a result of this process, a sinc function modulating the complex amplitude distribution of the objects is produced in the back focal plane of the lens. Therefore, rainbow holography is achieved. Theoretical analysis and some experimental results are presented.