Materials for 3D optical storage: two-photon access vs. one-photon background

1. Materials for 3D optical storage: two-photon access vs. one-photon background N.S. Makarov, A. Rebane, M. Drobizhev (Department of Physics, Montana State University, Bozeman, MT 59717, USA) H. Wolleb, H. Spahni (Ciba Specialty Chemicals Inc, P.O. Box Ch-4002 Basle, Switzerland)

2. Outline • Principles of 3D 2PA optical memory • Lack of 2PA-sensitive photochromes • 2PA resonance enhancement • 2PA vs. 1PA • 2PA-sensitive phtalocyanines • Summary • References

3. Principles of 3D 2PA optical memory PD DM dv hv M dh hh write read nL nL nL nL form A form B form A form B

4. Lack of 2PA-sensitive photochromes Access with 1 pulse: 100fs, 100MHz => 1TB read/write in 22.2 hrs Each bit have to be written and read by only 1 femtosecond pulse!

5. 2PA resonance enhancement Wavelength, nm 700 800 900 1000 1100 Qx(A) 18000 Qy(A) 16000 14000 12000 s2, GM 10000 8000 6000 4000 long wavelength tail region 2000 0 15000 14000 13000 12000 11000 10000 9000 Frequency, cm-1 A fundamental trade-off between 2PA and 1PA may be formulated as follows: On the one hand, one would like to tune laser frequency as close as possible to the resonance in order to increase useful signal, but on the other hand, one would like to tune as far as possible to decrease detrimental background.

6. 2PA vs. 1PA 1 Fluorescence 240K 10-1 4.0 900 nm, a=2.14 ±0.16 10-2 I(P)= Pa 890 nm, a=1.99 ±0.05 3.5 880 nm, a=1.68 ±0.04 Absorbance, a.u. 870 nm, a=1.54 ±0.09 3.0 10-3 860 nm, a=1.36 ±0.10 850 nm, a=1.24 ±0.17 2.5 300K Fluorescence intensity, a.u. 10-4 2.0 240K 1.5 10-5 1.0 0 500 1000 1500 2000 2500 Frequency detuning n1PA-nL, cm-1 0.5 0.0 1 2 3 4 5 6 7 8 9 Laser pulse energy, a.u. 850-900 nm

7. 2PA-sensitive phtalocyanines 1 750 cm-1 2250 cm-1 1000 cm-1 2000 cm-1 1250 cm-1 SNR 1500 cm-1 1750 cm-1 2250 cm-1 2000 cm-1 2750 cm-1 Pc3Nc SNR 2500 cm-1 0.1 Pc3Nc Pc3An 2250 cm-1 1 3000 cm-1 Pc3An 0.01 1 10 100 1000 SBR 1E-3 0.01 0.1 1 10 SBR

8. Summary • Because of the requirement of fast speed writing and readout, the storage materials need to have high molecular 2PA cross section, 2>103-104 GM • It is evident that the crucial points in this approach are the two-photon sensitivity of a molecule and the possibility of its photochemical transformation from one form to another • Careful choice of excitation frequency, along with suitable combination of 1PA and 2PA properties allow minimizing the negative impact of underlying near resonance hot band absorption • Our model allows to predict the appropriateness of chromophores for the 2PA-based optical storage

9. References • D.A. Parthenopoulos, P.M. Rentzepis, “Three-Dimensional Optical Storage Memory”, Science, 245, 843-845 (1989). • M. Drobizhev, A. Karotki, M. Kruk, A. Rebane, “Resonance enhancement of two-photon absorption in porphyrins”, Chem. Phys. Lett., 355, 175-182, (2002). • M. Drobizhev, Y. Stepanenko, Y. Dzenis, A. Karotki, A. Rebane, P.N. Taylor, H.L. Anderson, “Understanding Strong Two-Photon Absorption in -Conjugated Porphyrin Dimers via Double-Resonance Enhancement in a Three-Level Model”, J. Am. Chem. Soc., 126, 15352-15353 (2004). • M. Drobizhev, F. Meng, A. Rebane, Y. Stepanenko, E. Nickel, C.W. Spangler, “Strong two-photon absorption in new asymmetrically substituted porphyrins: interference between charge-transfer and intermediate-resonance pathways”, J. Phys. Chem. B, 110, 9802-9814 (2006). • M. Drobizhev, Y. Stepanenko, Y. Dzenis, A. Karotki, A. Rebane, P.N. Taylor, H.L. Anderson, “Extremely strong near-IR two-photon absorption in conjugated porphyrin dimmers: quantitative description with three-essential-states model”, J. Phys. Chem. B, 109, 7223-7236 (2005). • M. Drobizhev, A. Karotki, M. Kruk, N. Zh. Mamardashvili, A. Rebane, “Drastic enhancement of two-photon absorption in porphyrins associated with symmetrical electron-accepting substitution”, Chem. Phys. Lett., 361, 504-512 (2002). • I. Renge, H. Wolleb, H. Spahni, U.P. Wild, “Phthalonaphthalocyanines: New Far-Red Dyes for Spectral Hole Burning”, J. Phys. Chem. A 101, 6202-6213, (1997). • A.A. Gorokhovskii, R.K. Kaarli, L.A. Rebane, “Hole Burning in Contour of a Pure Electronic Line in a Shpolskii System”, JETP Lett., 20, 216-218, (1974). • M. Drobizhev, A. Karotki, A. Rebane, “Persistent Spectral Hole Burning by Simultaneous Two-Photon Absorption”, Chem. Phys. Lett., 334, 76-82, (2001). • A. Rebane, M. Drobizhev, A. Karotki, Y. Dzenis, C.W. Spangler, A. Gong, F. Meng, “New two-photon materials for fast volumetric rewritable optical storage”, in: Proc. SPIE, Advanced Optical and Quantum Memories and Computing, Eds. H.J. Coufal, Z.U. Hasan, (SPIE, Belligham, WA, 2004), 5362, pp. 10-19. • M. Drobizhev, A. Karotki, M. Kruk, A. Krivokapic, H.L. Anderson, A. Rebane, “Photon energy upconversion in porphyrins: one-photon hot-band absorption versus two-photon absorption”, Chem. Phys. Lett., 370, 690-699 (2003). • A. Karotki, M. Drobizhev, Y. Dzenis, P.N. Taylor, H.L. Anderson, A. Rebane, “Dramatic enhancement of intrinsic two-photon absorption in a conjugated porphyrin dimer”, Phys. Chem. Chem. Phys., 6, 7-10 (2004). • M. Drobizhev, A. Karotkii, A. Rebane, “Dendrimer molecules with record large two-photon absorption cross section”, Opt. Lett., 26, 1081-1083 (2001). • M. Drobizhev, N.S. Makarov, A. Rebane, E.A. Makarova, E.A. Luk’yanets, “Two-photon absorption in tetraazachlorin and its benzo-and 2,3-naphtho-fused derivatives: Effective symmetry of -conjugation pathway”, J. Porphyrines and Phtalocyanines, Proc. Of the International Conference on Porphyrines and Phtalocyanines, ICPP-4, Rome, Italy, 2-7 July, 2006 (to be published).

10. M.E. Marhic, “Storage limit of two-photon-based three-dimensional memories with parallel access”, Opt. Lett., 16, 1272-1273 (1991). “For systems that use parallel access by simultaneous writing or reading of bits located in an entire common plane, diffraction sets a limit to the storage density that is far smaller than that for sequential operation. Comparable densities can be achieved by using a three-dimensional waveguiding structure.”