Second Harmonic Generation induced by optical poling in new TeO2-Tl2O-ZnO glasses

Article abstract of DOI:10.1016/j.materresbull.2010.01.024

New tellurite glasses with a large glass forming domain were elaborated within the TeO₂-Tl₂O-ZnO ternary system. The evolution of the glass transition (T_g) and onset crystallization (T₀) temperatures for such tellurite glasses was studied, in particular, as a function of the Tl₂O addition. A decrease of both T_g and T₀ temperatures was observed; the former being more affected. Structural modifications induced by the addition of the modifiers were studied by Raman spectroscopy. For a fixed ZnO concentration, the increase in the Tl₂O content leads to a destruction of the glass framework, characterized by the transformation of TeO₄ disphenoids into isolated TeO₃^2- trigonal pyramid-like ortho-groups. For a fixed Tl₂O concentration, the ZnO addition induces similar effects on the glass structure. The optical transmission of the ((80 - x)TeO₂-xTl₂O-20ZnO) (x = 10, 20 and 30 mol%) glasses was measured in the 300-2000 nm range. Their good transparency was evidenced and a clear reduction of the optical band-gap was noticed with the increase in the Tl₂O content. Finally, Second Harmonic Generation was unambiguously detected for each glass composition. The second order non-linearity amplitude is found to be increasing as a function of the Tl₂O concentration, in the tested range.

Full text of DOI:10.1016/j.materresbull.2010.01.024

Materials Research Bulletin 45 (2010) 551–557
Contents lists available at ScienceDirect
Materials Research Bulletin
journal homepage: www.elsevier.com/locate/matresbu
Second Harmonic Generation induced by optical poling in new TeO2–Tl2O–ZnO
glasses
a
a,
b
c
a
a
*
`
M. Soulis , J.-R. Duclere , T. Hayakawa , V. Couderc , M. Dutreilh-Colas , P. Thomas
a Laboratoire de Science des Proce´de´s Ce´ramiques et de Traitements de Surface, UMR 6638 CNRS, Universite´ de Limoges, Faculte´ des Sciences et Techniques, 123, avenue Albert Thomas,
87060 Limoges Cedex, France
b Department of Materials Science and Engineering, Nagoya Institute of Technology, Showa, Nagoya 466-8555, Japan
c XLIM-UMR 6172 CNRS, Universite´ de Limoges, Faculte´ des Sciences et Techniques, 123, avenue Albert Thomas, 87060 Limoges Cedex, France
A R T I C L E I N F O
A B S T R A C T
Article history:
New tellurite glasses with a large glass forming domain were elaborated within the TeO2–Tl2O–ZnO
ternary system. The evolution of the glass transition (Tg) and onset crystallization (T0) temperatures for
such tellurite glasses was studied, in particular, as a function of the Tl2O addition. A decrease of both Tg
and T0 temperatures was observed; the former being more affected. Structural modifications induced by
the addition of the modifiers were studied by Raman spectroscopy. For a fixed ZnO concentration, the
increase in the Tl2O content leads to a destruction of the glass framework, characterized by the
transformation of TeO4 disphenoids into isolated TeO32ꢀ trigonal pyramid-like ortho-groups. For a fixed
Tl2O concentration, the ZnO addition induces similar effects on the glass structure. The optical
transmission of the ((80 ꢀ x)TeO2–xTl2O–20ZnO) (x = 10, 20 and 30 mol%) glasses was measured in the
300–2000 nm range. Their good transparency was evidenced and a clear reduction of the optical band-
gap was noticed with the increase in the Tl2O content. Finally, Second Harmonic Generation was
unambiguously detected for each glass composition. The second order non-linearity amplitude is found
to be increasing as a function of the Tl2O concentration, in the tested range.
Received 12 December 2009
Accepted 29 January 2010
Available online 6 February 2010
Keywords:
A. Glasses
D. Optical properties
ß 2010 Elsevier Ltd. All rights reserved.
1. Introduction
[14,19,20], or TeO2–ZnO–Na2O, TeO2–BaO–ZnO, TeO2–ZnO–Li2O
and TeO2–ZnO–MgO glasses [19–23].
TeO2-based glasses are among the most promising candidates
for integration in non-linear optical devices, such as up-conversion
frequency systems, high speed optical-switches, since they exhibit
high linear and non-linear refractive indices, good visible and
infrared transmittance, high Raman gain performances, and since
their third-order non-linear optical susceptibility (x(3)) is among
the highest for oxide glasses [1–8].
Second Harmonic Generation (SHG) should be forbidden in
glass due to its isotropy. However, second order non-linearity can
be induced in glasses exposed to intense laser light (optical poling)
[9,10], or thermally treated under the application of an electric
field (thermal poling) [11]. Since then, both photo- and thermo-
electrically induced SHG have been reported several times in
various glass systems [12–23]. Among that list, some of the articles
are of particular interest for us, as their authors focus on thermal
and/or optical poling of TeO2-based glasses containing either Tl2O
or ZnO modifiers: namely TeO2–ZnO and TeO2–Tl2O glasses
We start by reviewing the relevant papers where the glass
forming domain in TeO2–ZnO and TeO2–Tl2O binary systems is
studied. Imaoka and Yamazaki, Wogel et al., Kozhukharov et al., as
well as Yakhkind reported on the glass forming domain in TeO2–
ZnO and TeO2–Tl2O systems [24–27]. In addition, in [28],
Jeansannetas et al. reinvestigated the TeO2-rich part of TeO2–
Tl2O system in order to properly establish the glass forming
domain, as a large dispersion of glass domain limits was found in
the above cited works (see Refs. [25,27]).
As we are extremely interested in the structural characteristics
of tellurite glasses, we review now the papers related to the
structure of such glasses and to its evolution as a function of the
concentration of Tl or Zn oxide modifiers. Mochida et al. showed
that the primary structural fragment of tellurite glasses containing
high TeO2 content is a distorted TeO4 bipyramid, and that the
fraction of TeO3 trigonal pyramids increases with an increase in the
mono- or di-valent cations [29]. The structure of MO–TeO2 glasses
(with M being a divalent cation: Mg, Sr, Ba or Zn) [30], as well as the
structure of MO1/2–TeO2 glasses (with M being a monovalent
cation: Li, Na, K, Rb, Cs and Tl) [31], was studied by Sekiya et al.,
using Raman spectroscopy. In [30], they indicated that the
* Corresponding author. Tel.: +33 5 55 45 74 62; fax: +33 5 55 45 74 03.
E-mail address: jean-rene.duclere@unilim.fr (J.-R. Ducle`re).
0025-5408/$ – see front matter ß 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.materresbull.2010.01.024

552
M. Soulis et al. / Materials Research Bulletin 45 (2010) 551–557
structure of MgO–TeO2 glasses, with low MgO content, is a
continuous network composed mainly of TeO4 trigonal bipyr-
amids (or TeO4 disphenoids) and TeO3+1 polyhedra. Then, with the
addition of MgO, the fraction of tellurium atoms forming TeO3
45]. The publications referenced [43–45] are extremely inter-
esting, as they justify the use of tellurite glasses for rare earth
doping, due to their low phonon energies (one of the lowest
among oxide glasses). In particular, the luminescence and up-
conversion properties (like up-conversion efficiency) are de-
tailed in those publications. As a last illustration, very recently,
Jaba et al. reported the effects of the Er2O3 content on the local
structure and on spectroscopic properties of Er3+-doped zinc
tellurite glasses [46].
As mentioned above, this list is far from being exhaustive but
testifies already to the intense and diverse research activities in the
field of TeO2-based glasses. Finally, we would like now to end up
this introduction by stating why we selected the TeO2–TlO0.5–ZnO
ternary system as a matter of new investigations. First, some
anterior work was carried out in our research group on optical
poling of glasses elaborated within the TeO2–ZnO or TeO2–Tl2O
binary systems. Indeed, Vrillet et al. reported in [14] that SHG can
be optically induced for such glasses. Furthermore, as stated in
[39], x(3) values of thallium tellurite based glasses are among the
highest values for tellurite glasses. It is therefore expected to also
obtain high third order optical non-linearities, and to be able to
generate a second harmonic, for glasses elaborated in the TeO2–
TlO0.5–ZnO ternary system. Indeed, we suspect that Tl2O will
favour the hyperpolarisability (x(3)) and that ZnO will increase the
thermal stability and improve the optical damage threshold.
Moreover, as indicated in Fig. 1, the glass forming domain limits for
the binary systems are relatively extended. Thus, one expects the
existence of a large glass forming domain in the case of the ternary
system, allowing some simple and easy elaboration of pellets
suitable for optical poling tests. All these combined reasons justify
our selection.
trigonal pyramids increases. When the MgO content exceeds
2ꢀ
40 mol%, then, isolated structural units, such as TeO3
and
Te3O84ꢀ ions, are formed in glasses. Based on the similar shapes of
their Raman spectra and a great resemblance of compositional
dependences of Raman peak intensities, they assumed that ZnO–
TeO2 glasses have the same structure as those of MgO–TeO2
glasses. Hence, the structure of ZnO–TeO2 glasses will be modified
in a similar manner with the addition of ZnO. In [31], Sekiya et al.
showed that the structure of thallium tellurite glasses with less
than 30 mol% TlO0.5 is similar to that of alkali tellurite glasses
containing equal amounts of MO0.5 (with M being Li, Na, K, Rb or
Cs). In alkali tellurite glasses, they also observed that the fraction
of TeO4 trigonal bipyramids decreases with increasing alkali
content. Thus, the same tendency to break the continuous
network constructed by sharing corners of TeO4 disphenoids is
observed with the addition of thallium oxide. Jeansannetas et al.
[32], as well as Noguera et al. in [33], also evidenced the
progressive transformation of TeO4 units into island-type TeO3
ortho-anions with increasing Tl2O content. They reached then the
same conclusions as Sekiya et al. in [31], concerning the
depolymerization of thallium tellurite glasses with an increasing
Tl2O content. Jeansannetas et al. reported also on the relationships
between the glass structure and the optical non-linearities in
TeO2–Tl2O glasses. For that particular type of thallium tellurite
glasses, they measured one of the highest non-linear refractive
index at 1.5
m
m (n2 = 9 ꢁ 10ꢀ19 m2/W) [32]. In addition, Soulis et
al. detailed the role of the modifier’s cation valence on the
structural properties of various TeO2-based glasses, and in
particular, for TeO2–Tl2O glasses [34]. Like Sekiya et al. [31],
they also attributed each Raman band to a specific vibration. We
simply mention as well that the structure of TeO2–ZnO glasses
was investigated by Shimizugawa et al., using another technique
than Raman spectroscopy: EXAFS [35].
Therefore, this work is mainly dedicated to report the feasibility
to elaborate new glasses in the TeO2–Tl2O–ZnO ternary system,
suitable for optical characterizations. In such chemical system, a
large glass forming domain was evidenced. The thermal, as well as
the structural characteristics of the glasses were determined. The
influence of the thallium oxide content on the aforementioned
characteristics was particularly investigated. This paper finally
relates the possibility to generate a Second Harmonic, induced by
optical poling, in those glasses. Second Harmonic Generation
We will list finally, not exhaustively, other studies of interest
for us and which are focused on glass forming domain, structural
investigations, and linear or non-linear optical properties of
glasses elaborated mainly within TeO2–ZnO- and TeO2–Tl2O-
based ternary systems. Berthereau et al. published the thermal
properties, the densities, as well as the optical properties (linear
(n0 and optical transmission) and non-linear refractive indices
(n2)) of various TeO2-based glasses, and in particular, of binary
TeO2–ZnO glasses [36]. Chagraoui et al. have evidenced a small
glass forming domain in the ZnO–Bi2O3–TeO2 system [37].
Recently, Udovic et al. published the formation domain, and the
thermal and structural characterizations of new glasses within
the TeO2–TiO2–Tl2O system [38]. In particular, they studied the
role of Tl2O and TiO2 modifiers on the glass structure and on the
physical properties. It was found that Tl2O favours the non-
linear optical properties, whereas TiO2 improves their thermal
and mechanical stabilities. Dutreilh-Colas et al. have measured
the x(3) values for glasses elaborated within various ternary
systems, namely TeO2–Tl2O–Bi2O3, TeO2–Tl2O–PbO and TeO2–
Tl2O–Ga2O3 [39]. In particular, for the TeO2–Tl2O–PbO glasses,
they measured x(3) values almost 10 times higher than those of
SF59 glasses, justifying again the interest for such thallium
tellurite-based chemical systems. Furthermore, for TeO2–Tl2O
and TeO2–Tl2O–PbO glasses, Stegeman et al. have measured
some Raman gain coefficients up to 50–60 times that of a
3.18 mm thick Corning 7980-2F fused silica sample [40]. In
addition, we now briefly enumerate some examples of the
literature where TeO2–ZnO-based glasses are doped with rare
earth ions (e.g. Eu2+, Er3+, and Ho3+) for optical applications [41–
Fig. 1. Glass forming domain within the TeO2–TlO0.5–ZnO ternary system. All the
tested compositions lead to glass formation, except compositions labeled 1, 12 and
18, where crystalline phases are obtained. The dashed lines indicate the limits of the
glass forming domains for TeO2–TlO0.5 and TeO2–ZnO binary systems.

M. Soulis et al. / Materials Research Bulletin 45 (2010) 551–557
553
amplitude, as well as optical transmission data, was measured as a
function of the thallium oxide content.
2. Experimental procedures
Glasses were prepared by melting intimately various quantities
of TeO2, Tl2CO3 and ZnO powders, in platinum crucibles, at 700 8C
for 20 min. Tl2CO3 and ZnO were commercial products (Aldrich
99.9%) and TeO2 was prepared from the decomposition at 550 8C,
under air, of the H6TeO6 orthotelluric acid (Aldrich 99.9%). The
melts were air-quenched into a brass ring, deposited over a pre-
heated brass block, to obtain cylindrical samples 10 mm wide and
3 mm thick. The glass samples were then annealed 40 8C below
their glass transition temperature for 10 h in order to release the
thermal stresses resulting from the quenching. Both heating and
cooling ramps were carefully fixed at a low value (28/min). X-ray
diffraction was used to verify the glassy state of the samples. At the
Fig. 2. Sketch of the experimental set up used to generate and then read the second
order non-linearity. H: half-wave plates, L: lenses, F: filters, DC: doubling crystal, P:
polarizer, PD: photodiode, D: diaphragm, PMT: photomultiplier tube, F1: 2 green
blocking RG 850 filters, F2: 2 BG-18 colored glass filters (IR absorber), F3: 10 nm
band pass interference filter centered at 532 nm.
2000 nm range, at normal incidence, with a Varian Cary 5000
spectrophotometer operated in dual beam mode.
limits of the glass forming domain, either
compounds were evidenced.
a-TeO2 or ZnTeO3
The schematic representation of the experimental set-up used
to induce and read the second order non-linearity is shown in
Fig. 2. The light source was a pulsed Nd-YAG laser. It was
operated at a repetition rate of 10 Hz and with a pulse width of
20 ns. The output beam was frequency doubled in a Potassium
Titanyl Phosphate (KTP) crystal. The diameter of the laser beam
at the focal point was measured with an infrared camera and was
The thermal characteristics (i.e. glass transition and onset
crystallization temperatures) were determined with a commercial
differential scanning calorimetry apparatus. All the calorimetric
data measured for the various tested compositions are listed in
Table 1.
The vibrational spectra of all the glasses were recorded in the
200–900 cmꢀ1 frequency range, with a micro-Raman spectrometer
(Horiba-Jobin Yvon, T64000 model), equipped with a CCD detector
and an Ar+ laser (514.5 nm line). Raman experiments are performed
in a backscattering geometry, on powders resulting from the
grinding of the tellurite glasses before laser exposure. The diameter
estimated to be about 60
mm. The ratio between fundamental
(1064 nm) and SH (532 nm) lights was controlled by varying the
laser beam energy and the phase matching condition of the KTP
crystal with half-wave plates H1 and H2, respectively. In the
writing phase, both fundamental and SH light were collinearly
irradiating the sample, while in the reading phase two green
blocking RG 850 filters (F1) were introduced in the beam path, so
that only the fundamental light reached the sample. The SH light
intensity generated by the sample was detected by a photo-
multiplier tube. Any residual fundamental light was absorbed by
2 BG-18 coloured glass filters (F2), which was followed by a
10 nm band pass interference filter centered at 532 nm (F3). The
of the laser spot focused at the sample was about
1 mm.
Measurements were carried out with a laser output power of
100 mW. The spectral resolution is about 4.5 cmꢀ1. We emphasize
that, after the poling experiments, we briefly checked the irradiated
areas: no particular sign of crystallization was evidenced.
Among the elaborated glasses, three of them were selected and
then mechanically polished to obtain plane discs suitable for the
optical characterizations. The corresponding chemical composi-
signal was measured on an oscilloscope, triggered by
photodiode.
a
tions of such glasses are the following: (80 ꢀ x)TeO2–xTlO0.5
–
20ZnO, where x is equal to 10, 20 and 30 mol%, respectively. The
Each poled area was systematically irradiated first by the
fundamental wave (i.e. = 1064 nm) in order to verify that no SH
optical transmission measurements were carried out in the 300–
l
Table 1
signal was detected. In addition, we systematically paid extreme
attention to discriminate in between true Second Harmonic
Generation and green-fluorescence. Each glass was poled with
the same PPD /PPD2 ratio between fundamental and SH lights
Table summarizing all the information (chemical composition, crystallographic
nature, calorimetric data) related to all the elaborated materials. Tg, T0 correspond
respectively to the glass transition and to the first onset crystallization
temperatures. Data highlighted in bold font correspond to a varying TlO0.5 content,
while maintaining a fixed ZnO content.
v
v
(PPD stands for Peak Power Density). PPD1064 and PPD532 poling
values were measured with an energy meter or some photodiode,
and are equal to 0.24 and 0.13 GW/cm2, respectively. PPD1064
reading value is equal to 0.19 GW/cm2. If PPDs were adjusted in
order to avoid any laser damage of the glasses, the PPD /PPD2
Sample
number
Chemical
Specific
Sample nature
composition (mol%)
temperatures (8C)
TeO2
TlO0.5
ZnO
Tg
T0
T0 ꢀ Tg
v
v
1
2
80
75
70
70
70
65
65
60
60
60
55
55
50
50
50
45
45
40
10
5
10
20
10
16
20
20
30
10
20
30
20
40
10
20
30
10
20
35
x
x
x
a-TeO2
ratio still remains to be adjusted in order to optimize the amplitude
of SHG. As well, we point out that PPDs are approximately one
order of magnitude lower than the ones reported in [14],
suggesting very likely in our case (i.e. nanosecond pulses), that
additional effects (mainly thermal effects) would play a role in the
poling process (see discussion later). In addition, for each glass, we
systematically recorded two sets of data collected from two
different poled areas: the SHG intensities were then averaged.
Finally, according to some theoretical background [47], as the
amplitude of the second order non-linearity is proportional to the
square of the thickness of the probed medium, the raw SHG data
have thus been normalized to the square of each sample thickness.
In our SHG measurements, we finally estimate the error bars to be
about 10%. The error bars include the slight energy fluctuations of
the laser that we noticed.
314
249
275
293
274
318
207
250
299
228
x
375
314
346
358
362
388
350
347
354
323
x
61
65
71
65
88
70
143
97
55
95
x
Amorphous
Amorphous
Amorphous
Amorphous
Amorphous
Amorphous
Amorphous
Amorphous
Amorphous
Amorphous
ZnTeO3
3
20
14
10
15
5
4
5
6
7
8
30
20
10
25
5
9
10
11
12
13
14
15
16
17
18
40
30
20
45
35
25
164
206
252
125
181
x
325
319
311
200
308
x
159
113
59
75
127
x
Amorphous
Amorphous
Amorphous
Amorphous
Amorphous
ZnTeO3

554
M. Soulis et al. / Materials Research Bulletin 45 (2010) 551–557
3. Results and discussion
Various chemical compositions have been tested in the TeO2–
TlO0.5–ZnO system in the aim of elaborating samples (pellets)
suitable for SHG experiments. The TeO2–TlO0.5–ZnO ternary
diagram with all the tested compositions is displayed in Fig. 1. In
addition, all the corresponding data are gathered in Table 1.
Fig. 1 shows that a relatively large glass domain already exists,
even if the glass domain limits have not been strictly established
yet. Indeed, some compositions still remain to be explored, on
the Tl-rich side of the ternary diagram. The aspect (color) of the
glasses varies with the composition, from what looks like
completely transparent (Zn-richer part) to yellowish (Tl-richer
part) glasses.
All the calorimetric data are listed in Table 1. In particular, we
wish to emphasize the strong effect of the Tl2O modifier
concentration on both Tg and T0 values. Fig. 3a indicates the
variation of both Tg and T0 values versus the Tl2O content, for a
constant ZnO content. Both Tg and T0 are reduced with the increase
in the Tl2O content; the former being more affected. Such variation
of the glass transition temperature was already observed in the
case of TeO2–Tl2O binary glasses [31,32]. As a consequence, the
(T0 ꢀ Tg) difference, which reflects the thermal stability of the
glass, is increased as indicated in Fig. 3b. Such results constitute
some interesting information in case of potential fiber-drawing
applications.
According to Fig. 3c, when considering now a varying ZnO
content, for a constant Tl2O content, the glass transition tempera-
ture remains constant. However, for glasses elaborated within the
binary TeO2–ZnO system, Sekiya clearly showed that the ZnO
addition leads to an increase in the glass transition temperature
[48]. This evolution of Tg can then be understood if one considers,
in the case of the TeO2–TlO0.5–ZnO ternary system, the effects of
both Tl2O and ZnO modifier concentrations simultaneously. In fact,
while increasing the Tl2O content for a constant ZnO concentration,
the Tl/Te ratio directly increases (main contribution) and, at the
same time, the ZnO/Te ratio indirectly increases (minor contribu-
tion). On the other hand, while increasing the ZnO content for a
constant Tl2O concentration, the Zn/Te ratio directly increases
(main contribution) and, at the same time, the Tl/Te ratio indirectly
increases (minor contribution). Therefore, the evolution of Tg
represented in Fig. 3a can be mainly attributed to the Tl2O addition,
whereas the evolution of Tg showed in Fig. 3c could be explained by
the two antagonistic effects of the addition of ZnO and Tl2O oxide
modifiers.
The vibrational properties of the elaborated glasses were
studied with Raman spectroscopy. The evolution of the Raman
spectra, as a function of the Tl2O content, for a fixed ZnO
concentration, and as a function of the ZnO content, for a fixed Tl2O
concentration, is displayed in Fig. 4a and b, respectively. As was
discussed in [33], several bands can be clearly identified:
-
a first one, located at roughly 660 cmꢀ1, corresponding to the
symmetric stretching vibration of the equatorial Te–O bonds
within the TeO4 groups.
Fig. 3. (a) Evolution of both Tg and T0 versus the TlO0.5 content; (b) evolution of the
Tg ꢀ T0 difference versus the TlO0.5 content; (c) evolution of both Tg and T0 versus
the ZnO content. The dotted lines are present only as guides for the eyes.
-
-
a second one, located at roughly 740 cmꢀ1, corresponding to the
2ꢀ
symmetric synchronous vibration of the TeO3 ortho-anions.
a third one, located at roughly 445 cmꢀ1, corresponding to the
bending deformation of the Te—Oꢂ ꢂ ꢂTe bridges, mixed with the
axial Te–O bond stretching.
intensity change corresponds to the transformation of TeO4
disphenoids into [TeO3]2ꢀ trigonal pyramid-like ortho-groups,
which reflects the depolymerization of the glass. Such
a
-
a fourth and weak one, located below 300 cmꢀ1, corresponding to
the bending deformation of O–Te—O angles.
modification of the TeO2 glassy framework into island-type
ortho-tellurite structures was already observed for both TeO2–
ZnO and TeO2–Tl2O binary systems, respectively [30–32], and thus
occurs as well for the TeO2–TlO0.5–ZnO ternary system. The
progressive decay of the band near 445 cmꢀ1 gives the real
evidence for the disappearance of the TeO2 framework which
The data in Fig. 4a and b clearly indicate the relative intensity
increase of the second band in respect to the first one, as a function
of the addition of either Tl2O or ZnO modifiers, respectively. This

M. Soulis et al. / Materials Research Bulletin 45 (2010) 551–557
555
Fig. 4. (a) Superimposition of the normalized Raman spectra for glasses presenting
various TlO0.5 contents, for a constant ZnO content: X labels the molar percentage in
TlO0.5. (b) Superimposition of the normalized Raman spectra for glasses presenting
various ZnO contents, for a constant TlO0.5 content: X labels the molar percentage in
ZnO.
Fig. 5. (a) Optical transmission data for the (80 ꢀ x)TeO2–xTlO0.5–20ZnO glasses
(with x = 10, 20 or 30 mol%), in the 300–2000 nm range. Insert: magnification of the
300–800 nm range in order to highlight the red-shift of the optical transmission/
absorption edge. The optical transmission of a
matter of reference. (b) Absorption coefficient
The arrow points out the red-shift of the optical transmission/absorption edge.
a
a
-TeO2 single crystal is indicated as a
(cmꢀ1) in the 350–800 nm range.
2ꢀ
transforms into isolated TeO3 units (see [33,34]). Such decay is
we have derived the refractive index n from the optical
more pronounced in Fig. 4a than in Fig. 4b, as the Tl/Te ratio varies
from 0.067 to 0.6 (i.e. a variation of a factor of 10), whereas the Zn/
Te ratio varies from 0.14 to 0.6 (i.e. a variation of a factor of 4.2).
Here, the effect of each oxide modifier concentration increase is
identical, in the sense that it systematically leads to the
depolymerization of the glass framework.
transmission data, in the transparent region. In this region, the
optical transmission coefficient T can be related to the refractive
index by the formula:
2n
T ¼
n2 þ 1
At 2
mm, these values have been calculated and are reported in
Three glasses were selected (see Section 2) in order to study the
impact of the Tl2O addition on the optical properties. The optical
transmission data are represented in Fig. 5a, where a transmission
level slightly below 80% in the near infrared range is noticed. In the
1500–2000 nm range (transparent region), each sample presents
more or less the same optical transmission value, thus indicating
that the refractive indices are very similar (see below). However,
some discrepancies between the three glasses can be evidenced in
the visible range: indeed, the 70TeO2–10TlO0.5–20ZnO glass
seems to transmit less light than the two others (which behave
similarly). The reason of this difference is so far unknown. For
indication, the optical transmission values for the three glasses,
Table 2. The values obtained are perfectly compatible with what
was reported by El-Mallawany in [2], for a huge variety of tellurite
glasses, and in particular, for TeO2–ZnO and TeO2–Tl2O binary
glasses.
Finally, the approximate (reflections at the two glass-air
interfaces are not taken into account) absorption coefficient
a
Table 2
Optical transmission coefficient data at
the three listed glasses.
v and 2v, and refractive index at 2 mm, for
Glass composition
Optical transmission
Refractive
measured at
v(1064 nm) and 2v(532 nm), are listed in Table 2. In
coefficient T
index n
the insert of Fig. 5a, a magnification of the optical transmission in
the 300–800 nm range is represented. The optical transmission of
(at 2 mm)
T2 (532 nm)
v
T (1064 nm)
v
70TeO2–10TlO0.5–20ZnO
60TeO2–20TlO0.5–20ZnO
50TeO2–30TlO0.5–20ZnO
0.682
0.739
0.735
0.763
0.790
0.785
2.08
2.05
2.04
a a-TeO2 single crystal is given as a reference in order to highlight
the noticeable red-shift of the absorption/transmission threshold
with the increase in the Tl2O content of the glass. For each glass,

556
M. Soulis et al. / Materials Research Bulletin 45 (2010) 551–557
We emphasize first that our experimental conditions to induce
the poling process are different from those reported in [14], in the
case of TeO2–Tl2O glasses. In our case, we have used nanosecond
pulses (20 ns) with PDD of about 10 times lower than in [14],
whereas they used picosecond pulses (80 ps). Therefore, in our
experimental conditions, we cannot rule out thermal effects during
the poling process, which was excluded in [14]. The first probable
signature of the existence of thermal effects would be the fact that
saturation of the SH signal is reached faster than in [14]. This will
be discussed in more details below.
We cannot directly and strictly compare our data with the data
reported in [14]. First, as explained immediately above, the
temporal poling regimes are different. Then, the composition, and
thus the structure, of the analyzed tellurite glasses are different.
We are indeed working on ternary glasses whereas Vrillet et al.
carried out SHG experiments on binary glasses. However,
comparing these two sets of data still remains very interesting
and, somehow, relevant. In addition, one has to admit that optical
poling data available in the literature for similar tellurite systems
are unfortunately limited to the results reported in [14], which are
mainly focused on TeO2–ZnO or TeO2–Tl2O binary glasses.
Our data indicate that the SHG amplitude seems to be
increasing with the increasing Tl2O content (Fig. 6a). However,
Vrillet et al. previously noticed a reduction of the SHG amplitude
with increasing Tl2O content [14], thus, apparently, in contradic-
tion with our observations.
Nevertheless, this observation/conclusion should be moderated
in light of the above and following comments. First, our data
concern lower Tl2O content (in our case, from 10 to 30 mol%) than
the ones discussed in [14], where the Tl2O content varies from 25 to
50 mol%. Thus, one cannot immediately compare the two
concentration ranges. As an argument, the SHG amplitude could,
for instance, saturate for a Tl2O concentration around 25–30 mol %,
and decrease for higher Tl2O contents. If one admits the latter
assumption, our data are not in contradiction with the data
published in [14]. Moreover, our data concern poled ternary
glasses. Thus, the effect of the second modifier cation (i.e. Zn) must
be taken into account in order to be rigorous. Vrillet et al. reported
a strong increase in the SHG amplitude for poled TeO2–ZnO glasses
[14]. The amplitude was approximately multiplied by a factor of 10
for ZnO contents ranging from 20 up to 35 mol%, and then
decreased for a ZnO content of 40 mol%. In our case, the ZnO
content is fixed to 20 mol% but we have previously mentioned that
the Zn/Te ratio indirectly increases, as Tl2O is incorporated. In fact,
the combined effects of both ZnO and Tl2O modifiers could result in
an increase of the SHG signal. Thus, it appears that the results
extracted from [14] could become now compatible with our
measurements.
Fig. 6. Normalized Second Harmonic Generation intensity versus time for the
(80 ꢀ x)TeO2–xTlO0.5–20ZnO glasses (with x = 10, 20 or 30 mol%). (a) During the
poling process of the non-linearity, with PPD1064 = 0.24 GW/cm2 and
PPD532 = 0.13 GW/cm2. (b) During continuous reading process, after 10 min
poling of the 60TeO2–20TlO0.5–20ZnO glass, with PPD1064 = 0.19 GW/cm2. The
dotted line is present only as a guide for the eyes.
was directly derived from the optical transmission data, using the
following formula:
1
a
¼ ꢀ lnðTÞ;
d
where d corresponds to the sample thickness, and
a is expressed in
cmꢀ1. Fig. 5b indicates the evolution of the absorption threshold as
a function of the Tl2O content. These data also clearly testify to the
red-shift of the absorption/transmission threshold, reflecting that
the optical band-gap is reduced with the increase in the Tl2O
content.
Finally, our SHG data for poled TeO2–Tl2O–ZnO glasses should
be compared to the non-linear optical properties of ‘‘similar’’
thallium tellurite glasses. The term ‘‘similar’’ should be understood
in the sense that the second oxide modifier, ZnO, could be for
instance replaced by PbO. The third order non-linear susceptibility
As mentioned in Section 1, previously in our laboratory, Vrillet
et al. demonstrated the generation of a second harmonic signal in
optically poled glasses elaborated in several binary systems, and
in particular in the case of TeO2–TlO0.5 and TeO2–ZnO systems
[14]. In this present work, we unambiguously evidence the
generation of a second order non-linearity optically created in
those new TeO2–TlO0.5–ZnO glasses. This is showed in Fig. 6,
where the SHG intensity is displayed as a function of the poling
and reading time, respectively. The poling curve (Fig. 6a) is typical
for poling experiments. Indeed, the SHG amplitude saturates after
a few minutes of exposure of the glasses: we consider that a
poling time of 5–10 min is typically sufficient to saturate the SHG
signal.
(
x(3)) was measured, for TeO2–Tl2O–PbO glasses. The measure-
ments revealed an increase of the x(3) value with the increase in the
Tl2O content, for various fixed PbO contents [39]. In particular, the
x(3) value for the three glasses of the following compositions
(70TeO2–10TlO0.5–20PbO, 64TeO2–16TlO0.5–20PbO and 56TeO2–
24TlO0.5–20PbO) was measured at 0.8
mm, using a Mach-Zehnder
interferometer. We selected intentionally such compositions as the
PbO content is equal to 20 mol% (comparable to 20 mol% in ZnO).
The respective x(3) values were obtained: 320, 433 and
567 ꢁ 10ꢀ23 m2/V2. Interestingly, for similar Tl2O contents, it
can be noticed that the x(2) amplitude detected for our TeO2–Tl2O–
ZnO poled glasses follows exactly the same trend as the x(3) value
measured for TeO2–Tl2O–PbO glasses [39]. These results are then

M. Soulis et al. / Materials Research Bulletin 45 (2010) 551–557
557
relatively similar as it is believed that x(3) is related to x(2) via the
[4] A. Mori, H. Masuda, K. Shikano, K. Oikawa, K. Kato, M. Shimizu, Electron. Lett. 37
(2001) 1142.
[5] V.V. RaviKanthKumar, A.K. George, J.C. Knight, P.St.J. Russell, Opt. Express 11
(2003) 2641.
following relationship: x(2)
internal electric field [49,50].
=
x(3) ꢁ Edc, where Edc represents the
[6] A. Mori, JCS-Japan 116 (2008) 1040.
The SHG decay curve (Fig. 6b) is measured after a poling time of
10 min, for a unique glass of the following composition: 60TeO2–
20TlO0.5–20ZnO. As stated earlier, we know after such poling time of
10 min (see Fig. 6a), that the SHG signal is saturated. Thus, assuming
an exponential decay for the erasing of the SHG signal during the
reading process, one obtains a time constant of about 37 min. Such
value is approximately 6 times higher than the one reported in [14]
in the case of a 70 mol% TeO2–30 mol% ZnO glassy sample. Despite
the difference in the chemical nature of the systems, we suspect that
thermal effects play here the main role in order to explain why the
SHG signal lasts for so long. Indeed, in our case, only slightly more
than 60% of the SHG signal is lost after 40 min of continuous reading,
whereas in [14], 75% of the SHG signal is lost after the same reading
time. Such observation suggests more persistency of the SHG signal,
after being poled with a pulsed nanosecond laser. However, as the
chemical nature of the systems is different, at this stage of the study,
it is impossible to draw any definite conclusion concerning laser
dynamics effects on SHG.
[7] R. Stegeman, L. Jankovic, H. Kim, C. Rivero, G. Stegeman, K. Richardson, P. Delfyett,
Y. Guo, A. Schulte, T. Cardinal, Opt. Lett. 28 (2003) 1126.
[8] A.P. Mirgorodsky, M. Soulis, P. Thomas, T. Merle-Mejean, M. Smirnov, Phys. Rev. B
73 (2006) 134206.
[9] U. Oesterberg, W. Margulis, Opt. Lett. 11 (1986) 516.
[10] R.H. Stolen, H.W.K. Tom, Opt. Lett. 12 (1987) 585.
[11] R.A. Myers, N. Mukherjee, S.R.J. Brueck, Opt. Lett. 16 (1991) 1732.
[12] Y. Yonesaki, K. Tanaka, J. Si, K. Hirao, J. Phys. Condens. Matter 14 (2002) 13493.
[13] Y. Yonesaki, K. Tanaka, A. Narazaki, J. Si, K. Hirao, J. Phys. D: Appl. Phys. 35 (2002)
2026.
[14] G. Vrillet, P. Thomas, V. Couderc, A. Barthe´le´my, J.-C. Champarnaud-Mesjard, J.
Non-Cryst. Solids 345 (2004) 417.
[15] K. Tanaka, K. Kashima, K. Hirao, N. Soga, A. Mito, H. Nasu, J. Non-Cryst. Solids 185
(1995) 123.
[16] K. Tanaka, A. Narazaki, K. Hirao, Opt. Lett. 25 (2000) 251.
[17] A. Narazaki, K. Tanaka, K. Hirao, N. Soga, J. Am. Ceram. Soc. 81 (1998) 2735.
[18] C. Lasbrugnas, P. Thomas, O. Masson, J.-C. Champarnaud-Mesjard, E. Fargin, V.
Rodriguez, M. Lahaye, Opt. Mater. 31 (2009) 775.
[19] K. Tanaka, K. Kashima, K. Kajihara, K. Hirao, N. Soga, A. Mito, H. Nasu, Second
Harmonic Generation in Electrically Poled TeO2 Based-Glasses, in: J. Michel,
Digonnet (Eds.), Proc. SPIE, vol. 2289, 1994, p. 167.
[20] A. Narazaki, K. Tanaka, K. Hirao, N. Soga, J. Appl. Phys. 85 (1999) 2046.
[21] K. Tanaka, A. Narazaki, H. Hirao, N. Soga, J. Appl. Phys. 79 (1996) 3798.
[22] K. Tanaka, A. Narazaki, K. Hirao, N. Soga, J. Non-Cryst. Solids 203 (1996) 49.
[23] A. Narazaki, K. Tanaka, K. Hirao, N. Soga, J. Appl. Phys. 83 (1998) 3986.
[24] M. Imaoka, T. Yamazaki, J. Ceram. Assoc. Jpn. 76 (1968) 160.
[25] W. Wogel, H. Bu¨ rger, F. Folger, R. Oehrling, G. Winterstein, H.G. Ratzenberger, C.
Ludwig, Silikattechnik 25 (1974) 206.
4. Conclusion
We reported on the possibility to elaborate new glasses in the
TeO2–TlO0.5–ZnO ternary system. The glass forming domain for the
elaboration of glassy pellets suitable for optical poling appears to
be already large, even if it is not fully established yet. The impact of
both Tl2O and ZnO addition on both calorimetric and structural
characteristics of the glasses was examined. The addition of each
oxide modifier clearly provokes a depolymerization of the glass
framework, as testified by the Raman spectroscopy data. Optical
properties, such as transmission data, were measured as a function
of the Tl2O content, evidencing a red-shift of the absorption/
transmission threshold with the increase in the Tl2O content; i.e. a
reduction of the optical band-gap. Finally, in this work, we
achieved our main goal, which was to prove the possibility to
generate a second order non-linearity in those new TeO2–Tl2O–
ZnO glasses. For the tested compositions, Second Harmonic
Generation was unambiguously detected after optical poling, with
a tendency for the SHG amplitude to be amplified by the Tl2O
addition. Work will be now focused on the study of the laser
dynamics (nanosecond or picosecond regime) on both the poling
efficiency and the SHG persistency. Work will be also to scrutinize
the poled regions using Raman spectroscopy in order to thoroughly
search for any potential structural changes of the glass after laser
exposure.
[26] V. Kozhukharov, M. Marinov, G. Grigorova, J. Non-Cryst. Solids 28 (1978) 429.
[27] A. Yakhkind, J. Am. Ceram. Soc. 49 (1966) 670.
[28] B. Jeansannetas, P. Marchet, P. Thomas, J.-C. Champarnaud-Mesjard, B. Frit, J.
Mater. Chem. 8 (1998) 1039.
[29] N. Mochida, K. Takahashi, K. Nakata, S. Shibusawa, Nippon Seram Kyo Gak 86
(1978) 316.
[30] T. Sekiya, N. Mochida, A. Ohtsuka, J. Non-Cryst. Solids 168 (1994) 106.
[31] T. Sekiya, N. Mochida, A. Ohtsuka, M. Tonokawa, J. Non-Cryst. Solids 144 (1992)
128.
[32] B. Jeansannetas, S. Blanchardin, P. Thomas, P. Marchet, J.-C. Champarnaud-Mes-
jard, T. Merle-Me´jean, B. Frit, V. Nazabal, E. Fargin, G. Le Flem, M.O. Martin, B.
Bousquet, L. Canioni, S. Le Boiteux, P. Segonds, L. Sarger, J. Solid State Chem. 146
(1999) 329.
[33] O. Noguera, T. Merle-Me´jean, A.P. Mirgorodsky, P. Thomas, J.-C. Champarnaud-
Mesjard, J. Phys. Chem. Solids 65 (2004) 981.
[34] M. Soulis, A.P. Mirgorodsky, T. Merle-Me´jean, O. Masson, P. Thomas, M. Udovic, J.
Non-Cryst. Solids 354 (2008) 143.
[35] Y. Shimizugawa, T. Maeseto, S. Inoue, A. Nukui, Phys. Chem. Glass. 38 (1997) 201.
[36] A. Berthereau, Y. Le Luyer, R. Olazcuaga, G. Le Flem, M. Couzi, L. Canioni, P.
Segonds, L. Sarger, A. Ducasse, Mater. Res. Bull. 29 (1994) 933.
[37] A. Chagraoui, A. Chakib, A. Mandil, A. Tairi, Z. Ramzi, S. Benmokhtar, Scripta Mater.
56 (2007) 93.
[38] M. Udovic, P. Thomas, A. Mirgorodsky, O. Masson, T. Merle-Mejean, C. Lasbrugnas,
J.-C. Champarnaud-Mesjard, T. Hayakawa, Mater. Res. Bull. 44 (2009) 248.
[39] M. Dutreilh-Colas, P. Thomas, J.-C. Champarnaud-Mesjard, E. Fargin, Phys. Chem.
Glass. 44 (2003) 349.
[40] R. Stegeman, C. Rivero, K. Richardson, G. Stegeman, P. Delfyett Jr., Y. Guo, A. Pope,
A. Schulte, T. Cardinal, P. Thomas, J.-C. Champarnaud-Mesjard, Opt. Express 13
(2005) 1144.
[41] M.R. Sahar, K. Sulhadi, M.S. Rohani, J. Non-Cryst. Solids 354 (2008) 1179.
[42] H. Xia, Q. Nie, J. Zhang, J. Wang, Mater. Lett. 57 (2003) 3895.
[43] T. Hayakawa, M. Hayakawa, M. Nogami, J. Alloy Compd. 451 (2008) 77.
[44] J.C. Boyer, F. Vetrone, J.A. Capobianco, A. Speghini, M. Bettinelli, J. Appl. Phys. 93
(2003) 9460.
Acknowledgements
This work was carried out within the frame of the national
project REGLIS. Some of the authors would like to thank as well the
[45] F. Vetrone, J.C. Boyer, J.A. Capobianco, A. Speghini, M. Bettinelli, Appl. Phys. Lett.
80 (2002) 1752.
[46] N. Jaba, H. Ben Mansour, A. Kanoun, A. Brenier, B. Champagnon, J. Lumin. 129
(2009) 270.
´
Region Limousin for its financial support.
[47] P.N. Butcher, D. Cotter, The elements of nonlinear optics, in: P.L. Knight, W.J. Firth
(Eds.), Cambridge Studies in Modern Optics, Cambridge University Press, 1990, 9.
[48] T. Sekiya, Structural study of tellurite glasses by Raman spectroscopy, PhD thesis,
1993.
[49] B.P. Antonyuk, Opt. Commun. 181 (2000) 191.
[50] B.P. Antonyuk, N.N. Novikova, N.V. Didenko, O.A. Aktsipetrov, Phys. Lett. A 287
(2001) 161.
References
[1] S.-H. Kim, T. Yoko, S. Sakka, J. Am. Ceram. Soc. 76 (1993) 2486.
[2] R.A.H. El-Mallawany, Tellurite Glasses Handbook: Physical Properties and Data,
CRC, 2001.
[3] J.S. Wang, E.M. Vogel, F. Snitzer, Opt. Mater. 3 (1994) 187.