Journal of Non-Crystalline Solids 95 & 96 (1987) North-Holland. Amsterdam
PHOSPHATE
LASER
H. Toratani, Hoya Optics, T.
GLASS
H. E. Inc.,
Izumitani,
S. E. Stokowski, California 94550,
701
OF ABSORPTION
Meissner Fremont,
Hoya
701 - 708
California
Corporation,
94538,
Tokyo,
Lawrence U.S.A.
OF 10-4cm-1
LOSS
Livermore
+
U.S.A.
Japan National
Laboratory,
Livermore,
We have experimentally determined loss coefficients of OH as 8.1x10-7cm-1/ ppm and of ionic platinum as 8.6x10-7cm-I/ppm for LHG-5 type phosphate laser glass without Nd203 doping. Glass has been produced with absorption loss of about 1x10-4cm-I which is one order of magnitude lower than is presently commercially available.
1. INTRODUCTION Lower
absorption
loss
and
an
increase
in
ful
for
diode
pumped
duced
phosphate
(430-650
loss
work
in
fibers
produced
phosphate' have of
been
glass
Losses
are
originating from
the
but
efforts positions
2.
loss
EXPERIMENTAL
2.1. A glass
+Supported
Glass
of
by
4f
laser
LHG-5,
and
-1
reduction silica
of glass
silicate'
and
applications to
metal
due
of due
glass
to
scalable
transition
absorption
by absorption
10-4cm-1
cm
lasers. the
fiber
readily
-3
to 1.5x10
multicomponent optical
pro-
large
shapes
slabs.
3d and
scattering for
to
is
or
materials; and
Hoya's
to
OH groups,
to
glass
of
high
(43
dB/km)
for
on
factors
ions,
Pt ion, depending
imperfections
quality.
mainly
introduced on
We report
commercial
contributing
melt-
causes
laser to
on glass
our com-
it.
PROCEDURE melting
composition
in
processes
1.0
relates
of for
use-
Currently
neodymium
majority
examples
plates
addition,
negligible
as
these
absorption
batch
material;
reduce such
of
of
thresholds
particularly
addresses
10 dB/km
than
losses of
lasing are
lasers.
literature the
lower loss
slab
wavelength the
some
less
amplifier
by
the
In are
to
as
caused
crucible
the in
process,
low
typically
is
in
of
zig-zag
Although
loss None
such
conditions.
losses
a CVll
with
from
exhibit
fibers.
reported.
laser
ing
by
glass
large
discussed
glass
results
Glasses
1.05um which
at
medium
apd
glasses
previously
optical
a lasing
efficiency.
miniature
laser
dB/km)
Most
of
slope
part
of
by
65
Lawrence
P205
-
12.5
Liver-more
A1203
National
0022-3093/87/.$03.50 0 Elsevier Science Publishers B.V. (North-Holland Physics Publishing Division)
- 22.5
Na20
Laboratory
(in
mol
'd) was
em-
H. Tornroni
702
ployed
for
with
the
Table
small
scale
composition
1 shows
suppliers.
1200°C
in
metal
experiments of
the All
coaniercial
impurity
content
glasses
furnaces
er 01. / Phosphore
were
which
while
larger
LHG-5
in
of
melted
were
scale
batch
Pt or
designed
to
gkm
melts
a prototype
glass in
her
were
materials
fused
carried
production as obtained
quartz
minimize
out
furnace. from
crucibles
at
contamination
by
about
transition
ions. Impurity
1
Table H3P04
contents
Fe
<
A1('N3
50
in
ppb
batch
materials < 50
Cu
< 300
ppb
< 50
NaN03
<
10
<
1
Na2C03
<
10
c
1
2.2.
Platinum
dissolution
To evaluate ial,
the
mined for
the
rate
at
of
preliminary
of
melts 3.
of
excluded the
EXPERIMENTAL Dissolution
Table
2 lists
was
of
optical
the
fused
inserted
crucible
quartz into
cleaned
9) was the
used
the
with
sample
is
mater-
was
deter-
melt
and
acid
measure
and
kept
its
absorption
detection
required
of
our
10 cm long
were
to
minimum
quality of
10-4cm-1
rate
rate
for
commercial to
Lamda
a 10 cm long
Pt
crucible
level for
glass
as
for
a 1 cm
determining
samples
in
a small
scale
samples.
measured
3
calorimetrically.
rates is
fused
contains
Pt the
Pt
dissolution
(1.1x10-‘cm/set)
grade
grade
materials
and
1200°C,
contaminate
purity
of
TM impurities
at
ventional
higher
of
remoyed,
Since
measurements
order
(2.3x10-7cJsec)
expected
from
that
RESULTS
3.1.
the
Elmer
' The poor reliable
of
Although
was
samples.
1x10-3cm-1
is
1x10-4cm-1.
Losses
as
plate
plate
(Perkin
evaluation
sample
quartz
the
originating
as well
measurement
A spectrophotometer
loss
fused
Then,
TM ions
Pt
imsasured.
Loss
long
glass
Pt and of
A Pt or times.
loss
2.3.
of
dissolution
12OO'C.
different
weight
in
effect
quartz
(99.95%).
glass
(99.99%)
lower
Pt
introduces
by
about
OH content
on
loss
crucible of
one
fused
for
quartz than
con-
materials
TM ions.
order
quartz.
fused
TM impurities
both levels
and
that
less
Therefore,
by comparable
of than
of
are
However, magnitude
lower
TM contents. 3.2.
Effect
Table
3 shows
calorimetric
of
OH the
measurements.
effect
of
at
1.05um
as obtained
from
H. Toromni
Table
2
TM impurities
Impurity
and
(ppm)
Dissolution
rate
Dissolved
content*
(wb)
Table
10 liter
3
of
glass
of
crucible
rate
703
materials
99.95%Pt
99.99%Pt
Fused
Fe
20
2
1
cu
5
1
0.16
o.17x1o-g
2.ox1o-g o.3x1o-g
Fe
1.7x1o-g
cu
o.43x1o-g
O.O8x1O-g
1.3
0.1
1.6
cu
0.33'
0.07
0.25
10 hrs
OH content
melting
on
Absorption la 3.35um
loss
Otl content*
cm-l
990
Loss
1
33.0
2
12.6
380
3
3.0
90
1.19
4
2.0
60
2.02
5
2.3
70
1.15
6
1.4
40
1.13
* OH content
is
estimated
quartz
2.3~10-~
Fe
crucible,
Effect
laser
1. 1x1o-g
(g/cm'/hr)
*
dissolution
(cm/s)
impurity
Impurity
er al. / Phosphate
ppm
@ 1.05um
8.9x10-4cm-1 3.2
as OH (ppm)
(cm-l)
= 3O.a
Ref.4
3.35um We estimate versus 100
the
OH content OH ppm appears
loss
coefficient
due
as 0.81x10-6cm-1/ppm to be insignificant
to
the
OH group
from
at 1.05um (Fig. 1). for obtaining levels
loss.
10
I
I
250
I
500
750
OH content FIGURE
1
Loss
coefficient
(ppm) due
to
OH
I
1000
a plot
of
loss
Loss due of 10 -4
to -1
OH below
cm
overall
704
H. Toramni
3.3.
Effect
Table
4 indicates
tribution is
of
below
of
the
ionic
ef al. / Phmphore
laser glass
platinum
the
effect
OH group
is
of
ionic
platinum
negligible
on
because
the
loss
at
1.05um.
OH content
of
The
these
con-
glasses
70 ppm.
. Table
4
Effect
of
Ionic
1
platinum
Pt
0 wm
on
loss
OH Content
Loss
40
1. 1 - 1. 2x10v4cm-l
- 70 ppm
200
70
3.0
3
500
40
5.44
We determine platinum
which
is
a loss of
almost (Fig.
of
platinum
ionic
ppm to
coefficient
about the
OH group
same
2).
due
as
that
Therefore, should
produce
the
be
a glass
_ the
‘:
content
d
of
less
than
with
3.4.
Effect
The ing
loss
time
after
of
at
does
not
17 hours
furnace
furnace
1.05um exhibit
loss
5). does
amounts
glass
of
of
melteven
Evidently, not
4
200 Ionic
to
FIGURE
5
Effect
Melting
lates
furnace
environment
time
on
OH Content
2
ionic
Loss
2 hrs
90
7
60
1.15
3
17
45
1.13
Prototype
the
we have for
geometry
coefficient
due
at
1.05um
wm
melts
point,
conditions
Loss platinum
1. 19x10e4cm-l
1
this
500 (ppm)
loss
2
3.5.
cess
of
Pt
the
to
At
0 i-----"
contribute
contaminants
8.6~10~~
t
the
melt.
Table
Slope:
$5 A .w m z
environment
change
1
10
b z.
about
overall
function any
(Table
environment
significant
as
1.05um
to
0.84x10-6cm-1/ppm
1x10-4cm-1.
of
at
82
ionic
100
ionic
attained
melting of
commercial
glass
sufficient in scale
a 0.5
understanding liter
production
prototype melters.
about
necessary
furnace
which
The
results
prosimusuggest
H. Toraroni
that
phosphate
laser
fully
produced
plates
when
4.
DISCUSSION
Table
1 lists
loss
of
10-4cm-1
able
as
laser
140
ppb
due loss
at
These
in impurity
1.05pm
laser
high
can
slabs
be
success-
and
amplifier
purity.
Co'+,
vary
with
be
for
Co'+,
glass
and
be
for
Ni2+
ppb
the
valence
dissolve to
less
in
ultra-
To achieve which
are
suit2+
than
47
ppb
for
Cu
and
590
ppb
for
V3+
re-
of
ions.
state
metallic 3+ Fe which
V3+
glass.2
compositions
should
350
converted
Ni2+,
a P205-Ge02-Ga203
content
for
ions Fe2+,
ultraphosphate
to
will
Cu2+,
data
the
2+
metal of
conditions Fe
705
at for
of
transition
1.05um
values
glass
TO LOSS 3d
ppb
required
materials
available
280
oxidizing most
to
and
Fe2+,
spectively.
Therefore,
batch
lawr
1x10-%m-1
of
shapes
coefficients
glass,
for
in
and
commercial
glasses5
melted
a loss
with
volume
OF CONTRIBUTIONS
Absorption
at
the
using
4.1.
phosphate
glass
in
er al. / Phosphore
platinum is
Laser
glass 6
inclusions.
known
to
absorb
,
is
less
1.05um. Table
6
Loss
coefficient
of
Loss
coefficient
Ion
2.4~10-~
Fe2+
0.7
2.4
co2+
0.35
Ni2+
0.28
v 3+
0.17 Ultraphosphate
B:
51.5P205-18.5Ge02-30 1 shows
about
loss 2.7x10
This
Table
5),
maximum loss
tribution crucible
68.2P205-1
their
1.8A1203-14
Ga203
the
maximum
contribution -4 -1 when cm , consistent
assuming
2,
mol
%)
5
that
(in
at
K20-6
content
1.05pm
applying the
(La+Nd)203
(in
%)
impurity
with the
wt
of
from the
the
batch
same
loss
of
impurity
6 also
allow
used,
Table
6 as
coefficients
calorimetrically
actual
materials
coefficients
to
measured concentrations
our
total were
loss
below
the
levels.
coefficients of
.
is
glasses
1.1
A:
Table
phosphate
(cm-l/ppm) B
than
The
in
2.3~10-~
composition.
stated
ions
A
Since
(e.g.
metal
cu2+
we estimate less
transition
of
impurities Using
which
experimentally
Table are
dissolved determined
an out
of
dissolution
assessment a platinum rates
of
the
maximum
or
fused
for
Pt
quartz and
fused
con-
706
H. Toramri
quartz
(Table
liter
2)
melt
terials. of
Therefore,
earth
due
extent
which
large
amounts
may not
be negligible.
efficient
is
3/2
which
Boltzmahn
cross
section
a weak
However,
equals
with
this
the
the
ground
the
is
that
at
1.05um
level,
is
5~10~’
10~10~~
1x1o-3
2x1o-3
a real
loss
case,
purer
but
to
by:
only
ions,
with
Nd203
should
99.99%
Since
the
10 weight
%
a loss
co-
be
used.
41 4
11/2level
I11,2
population
cross
given
but
with
as
transition
total
1.05um
for
such
the
thermal of
concentration
1~10~’
2 ppb
relatively
ppm even
levels
due
at
contains 100
harmful
emission
2x1o-4 not
often
most
the 5~10~~
stimulated
Nd203
are
transition.
coefficient
increasing
loss introduced
doping
In
about
ma-
since
They
20 to
the
lasing
is
to
Absorption
The
is
1.1
and
bands
suggests
of
Nd3'
ions.
The
absorption
section
which
is
due
about
k = Nox5x10-5x4x10-20
approximately
a decrease
of
as
inversion
shown:
density
in
0.97um.
although
2.87um
the
achieve on
efficient
not
loss data at
experimental
of of
value
should of
Absorption
due
absorption
bands to
and
affect
to
the
3.4,
presumed
This
less
than
of of
-1
, and
the is
1.44,
to
loss
is
at
2h30
absorption consistent
ppm co-
with
platinum to at
ionic 1.05um
platinum for
at higher
around
0.300
Pt
concentrations.
and
3.4
tolerable
ppm OH. 4
100
OH
at
mode
which
approximately
that
1 cm
coupled cause
fundamental
be
wave1.8,
absorption
likely to
OH groups to
indicates
about
is
the
various 2.0,
observed
effective
edge
at 2.6,
and mode
most
content
is
fibers 2.87,
predicted
absorption
1.05um
ionic
loss
optical
are
The
than
due
in about
vibration 1.1
fiber.
be
less
Broad
appear
of
glass
4.4.
3)
stretching
0.97
effect
loss at
between
be negligible. 10 -4 cm -1 at
silica
3.4um
of
observed
P-O-P at
the
will
a source are
A comparison
Absorptions
1.05um
OH
as
bands
that
vibration.
to
known
Absorption
1.28,
based
due
OH group
lengths.
(Fig.
are
platinum
Pm3+ increase
Nd203
Nd203
Sm3'
a 10
crucible
pumping.
4.3.
to
of
above
k (cm-')
optical
and
high
pure
the
ions
e.g.
absorption
inverse
N,(ions/cc)
and
3+
The absorption
increases
Since
in
of
level.
ions.
oxides, at
distribution
4x10-20cm2. and
ion. earth
l.lx10-5cm-1/ppm.
the cm -1
2000
the
metal
any
99.99%
Sm3+ and metal
active
Oy
use
for
10 -4 cm -'
as Oy 3+,
rare
has is
the
impurities
2 ppb
to
transition
contribution
about
itself
about
to
loss
of
Nd203
the
dissolved
than
3d transition
other
their
4f
at
laser glass
totally
less
necessary
such
provides
puri;y,
not
to
than
of
to
loss
impurities
a lesser
Nd203
is
affect
Absorption
Rare
of
amounts
it
do not
4.2.
4F
concentration
10 hrs
impurities
to
the
after
er -1. / Phosphore
0.43Oum The
our
H. Tororoni
ausorption fier
coefficient
of
in
fusion
discs
responds
to
laser
of
efficiency
0.2cm-1
and
(
of
100
total
ppm is
loss 100
at
systems
a concentration
concentration
CI al. / Phosphore
JUU
nm is
in
about
130
g/au
707
currently
terms
of
from
accepted
pumping
ppm of
acceptable -4 -1 10 cm .
of
her
ionic
the
for
ampli-
efficiency.
This
platinum.
viewpoint
' of
cor-
Therefore
both
the
pumping
Ionic
Pt
free
Thickness
of 1Onm
samples
1 400
FIGURE
5.
600
Wavelength
(nm)
Absorption
due
to
700
ionic
platinum
CONCLUSIONS Using
laser the
3
500
commercially glass
of
production Various
of
factor
ions
in
is
batch
which content
of
affect
loss
materials.
by
and
choosing
at
shapes
of
0.Blx10-6cm-1/ppm
controlled
purest loss
larger
factors
tant
about
available
1.1x10-4cm-1
batch 1.05pm laser at
impurities
such
The
of
effect
materials, in
slabs
and
1.05um as the
which
amplifier
were 3d
evaluated:
and
phosphate
scalable
The metal
of
respectively.
melting
melted is
to
discs.
transition
OH group
0.B6x10-6cm-1/ppm
appropriate
we have
a furnace
ionic Both
and
most
impor-
rare
earth
platinum
are
of
are
these
conditions.
ACKNOWLEDGEMENT We would measurements,
like
to and
A.
thank Pertica
F. Milanovich for
determining
and
R.
Robe1
some
of
for
the
the
absorption
calorimetric
loss spectra.
708
H. Tora~oni
el al. / Phosphare
laser glass
REFERENCES 1)
M. Yoshiyagawa, (1980) 489.
2)
T. Akamatsu,
3)
F. Milanovich E. Day
Y.
J.
Lightwave
and and
J.
Kaite,
R.
4)
0.
5)
S. E. Stokowski Society Symposia
6)
Laser Program Annual Liver-more, California,
Robel,
M. Stevels,
T.
Ikuma
Tech., to J.
and D. Kraskevich, Proc. 61 (1968) Report 1985, UCRL-50021-85
and
LT-1 be
T.
Kishimoto,
(1983)
J.
Non-Cryst.
Solids
580
published.
Non-Cryst. Defects 273. Lawrence (1985),
Solids, in
14
Glass,
Liver-more pp. 6-17
(1974) Materials
National to 6-21.
165. Research
Laboratory,
40