Two-photon 3D data storage

Keywords Two-photon absorption Fluorescence anisotropy Fluorine derivatives Two-photon 3D data storage Two-photon dynamic therapy ... 

Another interesting system that was studied for two-photon 3D data storage in our group is based on the modulation of fluorescent properties of 2PA chromophores by protonation [95]. For example, due to differences in basicity (pKb), fluorene 3 undergoes selective, stepwise protonation, first by proto-... 

Corredor CC, Huang Z, Belfield KD (2006) Two-photon 3D optical data storage via fluorescence modulation of an efficient fluorene dye by a photochromic diarylethene. Adv Mater 18 2910-2914... 

The use of two-photon processes is also being extensively studied in the use of photochromies in 3D data storage (Chapter 1, section 1.2.8.3) and in the holographic storage of data, which is covered in Chapter 5 (section 5.4). 

Due to the need to use expensive and complicated laser pump systems, early development occurred primarily by physicists. Two-photon absorption properties of existing materials were extensively studied in this stage. In early 1990s, some potential apphcations with this technique were demonstrated, such as two-photon fluorescence (2PF) 3D data storage [2] and 2PF microscopy [3]. However, the 2PA efficiency of the materials is the bottleneck for these applications, and this has triggered the effort to search for new materials with higher... 

To overcome volatility problems, two-photon absorption (TPA) is the most promising long-term data storage technique to date. TPA can be observed in all materials and lacks the noncentrosymmetric symmetry requirements of even-order nonlinear optical effects. Nevertheless, in centrosymmetric polymers two-photon absorption is allowed between states that have the same parity according to parity selection rules (112). Such a system has been demonstrated with nondestructive readout (113). Additionally, use of two-photon absorption on photorefractive polymer dispersed liquid crystals has been used to record a high 3D data density of 204.8 Gbits/cm (158). 

Figure 38 Photochromism-based 3D optical data storage, (a) The read-write mechanism using two different wavelengths (1064 and 532 nm) proposed by Renzepis etal. [54] (b) Spirobenzopyran absorbs a 1064 nm photon and a 532 nm photon to become merocyanin. (c and d) gives 1,2-bis(2-methyl-1-benzothiophen-3-yl)perfluorocyclopentene and 2-(1,2-dimethyl-3-indolyl)-3-(2,4,5-trimethyl-3-thienyl)maleic anhydride which are highly stable molecules with potential application in 3D optical data storage. The illustration of the write/read optics is reproduced with permission from ACS.

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