Multi-level recording of photochromic indolylfulgide

The photon-mode multi-level optical storage properties using a photochromic indolylfulgide compound named 2-(1-benzyl-3-methyl-2-indolylmethylene)-3-isoproplidene succinic anhaydride have been investigated. It has been found that this compound possesses an absorption maximum at 400 nm and undergoes a photocyclization upon irradiation with UV light at 365 nm, leading to the formation of a pinkish product with absorption maximum at 505 nm. By irradiation with visible light at 514.5 nm, the original absorption spectrum was recovered completely. The transmittance of this photochromic material was found to change nonlinearly along with the exposure energy, indicating the potential of this compound as multi-level optical storage material. Eight-level optical storage of amplitude modulation is experimentally realized using the indolylfulgide dispersed PMMA film for the first time. By employing the laser beam at 514.5 nm with power of 3 mW for recording and readout, multi-level signals with high signal-to-noise ratio (SNR) have been detected.