Page 608 - Book Hosokawa Nanoparticle Technology Handbook

APPLICATIONS 38 EXPRESSION OF OPTICAL FUNCTION

Figure 38.4
Photograph of images drawn inside the glass sample by
using a femtosecond laser: gray-colored image (after
femtosecond laser irradiation) and red-colored butterfly
(after femtosecond laser irradiation and further heat
treatment at 550 C for 1 h).

with a diameter of about 40 m was formed near the
focused area of the laser beam. Then, the glass sam-
ple was annealed at 550 C for 1 h. The laser-irradi-
ated part became red caused by plasmon resonance
shown in Fig. 38.4b after the heat treatment. By
Figure 38.3 using these phenomena, a red-colored butterfly and
Three-dimensional optical memory using the Sm 2 then a gold-colored image were obtained by further
luminescence at each 10 layer. annealing caused by the growth of Au particles
inside the glass sample, as shown in Fig. 38.4c. An
absorption spectra of the glass sample before and,
after the femtosecond laser irradiation and succes-
sive annealing at various temperatures for 1 h show
It is also demonstrated that the size distribution of that there was an apparent increase in (c)
nanoparticles can be controlled by the laser irradia- absorbance in the wavelength region from 300 to
tion conditions. This method should be useful not 800 nm in the irradiated region due to hole trap cen-
only for practical applications such as three- ters. It was suggested that a gold ion was reduced to
dimensional optical memory and fabrication of inte- a gold atom by capturing an electron from non-
grative all-optical switches, but also for controlling bridging oxygen during the femtosecond laser irra-
nucleation and crystal growth processes. After irra- diation and gold atoms aggregated to form
diation by the focused infrared femtosecond laser nanoparticles after the heat treatment. Fig. 38.5
with an average power of 300 mW and focused by a shows a TEM picture of precipitated gold nanopar-
10 objective lens with a numerical aperture of ticles in the femtosecond laser-irradiated part after
0.30 on each spot for 1/63 s, a gray-colored spot successive annealing at 550 C for 1 h, which were

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