As we can see from absorption spectra of glass 3
(figure 3) nanocrystalls of copper chloride were
formed in glass. The relative concentration of CuCl
in glass 1 and 3 can be estimated by absorption
spectra intensity. So, for the glass 3 it’s two times
more than for the glass1. So, we can say that the
concentration of CuCl in sample 3 it’s two times
more than for the sample 1, but the strongest
nonlinear optical limitting effect is in glass 1. Why?
Let’s discuss the figure 5. The temperature of full
disappearing of excitone in glass 1 is less than
150
ο
C, for glass 3 it’s 420
ο
C. It was shown in
(Golubkov et al, 2012), that there are two
characteristic temperatures of nanophase melting in
PAB glass. One of that melting points is near 150
ο
C
another one is at 270
ο
C. So, if we compare processes
of nanophase melting in PAB glass with similar
phenomena in silicate glasses with CuCl nanophase
(Dotsenko, Glebov, Tsekhomsky, 1998), we can say,
that temperature of excitone absorption disappearing
at 150
ο
C is the point of CuCl nanocrystalls melting
in glass 1. Point of CuCl melting in glass 3 is 361
ο
C.
It is known (Dotsenko, Glebov, Tsekhomsky, 1998;
Golubkov et al, 2012) that CuCl containing
nanophase can include another crystal components
which can affects on value of melting point of
nanophase. For CuCl-KCl eutectics such
temperatures can be 150⁰C. So, in glass 3 CuCl
nanophase can be “clear” and in glass 1 – nanophase
can contain mixed eutectic crystals of CuCl and
K
2
CuCl
3
.
The phase transition in such heterogeneous
material as a PAB glass with CuCl nanocrystalls can
induce the optical limiting effect because of
difference of refraction index of liquid CuCl-KCl
solution and glass host. Also, the melting of
nanophase can induce the growth of scattering and
growth of optical absorption in visible range
(including 532 nm).
In figure 5 the curves for glass 3 and 2 are
identical. That could be mean, that the mechanisms
of nonlinear limiting are the same in this glasses. As
it shown in figure 4, the luminescence bands in glass
2 and 3 are the same. We suggested that glass 2 and
3 has Cu
+
ions and (maybe) Cu
0
n
clusters after
comparing luminescence spectra with spectral
luminescence data at (Babkina et al, 2014). In the
article (Qiaohong et al, 2009) authors has shown that
metal clusters in glass can induce nonlinear optical
effects.
5 CONCLUSIONS
The new material with low-limit optical threshold
was synthesized – a PAB glass with copper chloride
nanocrystalls. Numerical value of threshold was
5x10
-6
Joules. This threshold is due of special
structure of nanophase of such glass, which contains
CuCl and K
2
CuCl
3
nanocrystalls. Such complicated
structure of nanophase gives low points of melting
of nanophase. That’s why during laser irradiation of
PAB-glass phase is melting and that’s induces the
appearance of additional color centers in glass.
It was shown that copper clusters also induce
nonlinear effects.
ACKNOWLEDGEMENTS
This work was financially supported by Russian
Scientific Foundation (Agreement # 14-23-00136).
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