Photochromic Polymer Composites for Two-Photon 3D Optical Data Storage

Abstract

In this paper we demonstrate 3D two-photon recording and two-photon readout in photochromic polymer composites containing a mixture of 1,2-bis(2-methylbenzo[b]thiophen-3-yl)hexafluorocyclopentene (diarylethene 1 ) and fluorene derivatives 2,2‘-(9,9-didecyl-9 H -fluorene-2,7-diyl)bis(ethene-2,1-diyl)bis(4,1-phenylene)) dibenzo[d]thiazole ( 2 ) or poly(9,9-didecyl-2,7-dipheylaminofluorene) ( 3 ). The recording mechanism in this system is based on two-photon excitation of the closed form of diarylethene 1 at 800 nm. The readout mechanism is based on the modulation of the emission intensity of fluorene derivatives 2 or 3 by the closed form of diarylethene 1 through Resonance Energy Transfer (RET). Föster distances ( R 0 ) and critical concentrations ( A 0 ) were calculated from the spectral overlap of the donor's emission (fluorene derivatives) and the acceptor's absorption (closed form of diarylethene 1 ) in solution and in polymer films of PMMA- co -VBP. This system was demonstrated to be suitable for recording data by two-photon excitation in thick storage media. The RET-based readout method proved to be essentially nondestructive (exhibiting a loss of the initial fluorescence emission less than 20% of the initial emission after 10 000 readout cycles), providing a solution to a long-standing challenge in photochromic optical data storage.