04-07-2012, 02:03 PM
3D optical data storage with two-photon induced photon-oxidation in C60-doped polystyrene film
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Introduction
Successful isolation and purification of macroscopic quantities
of fullerene clusters have generated in a huge amount
of interest in the physical and chemical properties of these
carbon structures. Fullerenes are now anticipated to have
a number of applications in future nano-photonics science
and technology.1–4) Recently, we successfully demonstrated
the three-dimensional (3D) optical data storage in C60 and
read from the enhanced fluorescence of the photo-oxidation5)
products.
Results and discussion
C60 has a complex absorption band structure extending from
400nm to 650 nm.7) The two-photon-induced fluorescence
from C60 is extremely weak, but the relative fluorescence
spectral distributions from one- and two-photon-excitation
are very similar (data not shown). This suggests that the
same excited states are reached regardless of the excitation
mode. Figure 1 shows the two-photon excitation fluorescence
spectra of C60-doped polystyrene film under Tiapphire laser
irradiation (910 nm, 100 fs, 82 MHz, and 50mW) in air. We
find that the fluorescence signal is weak with a broad peak
at about 730 nm before extended laser irradiation of the
sample in air, and after 30 s irradiation in air, the fluorescence
intensity increases 3-fold with a peak shift to about
715 nm.
Summary
We demonstrated 3D optical data storage with photooxidation
of C60 pumped by the fs Tiapphire laser. However,
the writing speed of our demonstration experiment is
still much too slow for practical use. Recently, we noted
that some polymer composites with C60 as the photosensitizer
could produce highly efficient optical property changes
under both one-and two-photon excitation with very fast response
times of several microseconds. Thus, very fast writing
can be achieved with such a memory system.