New two-photon materials for fast volumetric rewritable optical storage

Abstract

We study reversible photo-tautomerization induced by simultaneous two-photon absorption (2PA) in tetrapyrrolic molecules as a potential re-writable mechanism for fast, high-density volumetric optical memory. We show that by illuminating Br-tetra-ethyl-porphyrin (Br-TEP) with 150-fs pulses in the near-IR wavelength range the molecule can be switched between two tautomer forms with distinct spectral absorption-and fluorescence signatures in a fully reversible manner. The 2PA cross section in the illumination wavelength range 775-810 nm is measured and the figure of merit, F= φxσ 2 ~ 5x10 -53 cm 4 photon -1 s -1 is estimated for one of the tautomer forms of Br-TEP. Enhanced selectivity of 2PA-induced switching in the near-IR, with respect to one-photon excitation at the same transition energy is observed. We propose to overcome the limitation imposed by the small value of the 2PA cross section by introducing a new class of tetrapyrrolic molecules with greatly enhanced two-photon absorption efficiency. In this paper we present for the first time the structure and absorption properties of asymmetrical chlorin molecules with an attached 2PA-enhancing side group. Potential use of these new materials for high-density re-writable two-photon volumetric optical storage is discussed.

Phthalocyanine molecules with extremely strong two-photon absorption for 3D rewritable optical information storage

“…We have recently found that the photo-tautomerization reaction in tetrapyrroles can be initiated not only with onephoton absorption (1PA), but also with 2PA 12,13 . Another important observation stemming from our previous works 14,15 is that one can dramatically resonantly enhance the 2PA sensitivity of tetrapyrroles by tuning laser frequency closer to the first electronic 1PA transition from the low-energy side.…”