Photoinduced anisotropic properties of pyrrylfulgide are studied. From measurement of the photoinduced spectrum of dichroism, the birefringence spectrum is evaluated by Kramers-Kronig relations. At optimal exposure of 13 ~ 20J/cm2 a maximum photoinduced dichroism (Dperpendicular - Dparallel) of about 0.1 and a maximum photoinduced birefringence (nperpendicular - nparallel) of about 8×10-4 are achieved. We exploit this photoinduced anisotropy and use a pyrrylfulgide/PMMA film to demonstrate optical image processing such as contrast reversal, image subtraction and summation, low-pass filtering and edge-enhancement. From the spectra of dichroism and birefringence the spectrum of the diffraction efficiency for polarization holography is calculated. We demonstrate that diffracted images with high signal-to-noise-ratio (SNR) can be obtained by holographic recording with orthogonal polarization.
Two photochromic fulgides, 3-[2-(N, N-dimethylaniline)-5-methyl-xazolemethylene]-4-isopropylidenetetrahydrofuran-2, 5-dione (A) and 3-(1,2-dimethyl-5-phenyl-pyrrolmethylene)-4-isopropylidenetetrahydrofuran-2, 5-dione (B), doped in PMMA as candidates of dual-wavelength optical memory for parallel recording are demonstrated. With 488nm-laser and 650nm-laser, both “cross” and “star” images are recorded on the same place of the sample and readout. Cross-talk between two fulgide compounds in PMMA matrix is also investigated.
Optical data storage is a frontier in the information science. Currently, there are mainly two kinds of storage materials, i.e., thermal-optic and photonic materials. The storage methods are divided into serial and parallel modes. In the market, the mature technique is CD-RW, which uses the thermal-optic material and serial method. The storage density of the CD-RW is restricted by the size of material particles, the conduction of heat, etc. Besides, the recording speed is seriously limited by the process of heating. Photonic materials and parallel method will be the trend in the optical data storage. Because it is based on the photon reaction on the molecule scale, the storage density and speed will be greatly increased. In this paper, a new kind of organic photochromic material -- pyrrylfulgide was studied. A parallel optical data storage system was established. Using the pyrrylfulgide/PMMA film as a recording medium, micro-images and binary digital information could be recorded, readout and erased in this parallel system. The recorded information on the film can be kept for at least 8 months in dark at room temperature. So far, the storage density is 3 x 107 bit/cm2.