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FLUORIDE GLASSES – MATERIALS FOR
BULK LASERS AND
FIBRE OPTICAL AMLIFIERS
Michał Żelechower, Silesian University of
Technology, Katowice, Poland
1. What are fluoride glasses?
2. The role of rare earth elelments
3. Interaction of electromagnetic radiation with matter
a. Scattering, absorption, spontaneous and stimulated emission
b. Reconstruction of electron energy structure
c. Radiative and non-radiative transitions
4. Real structure of fluoride glasses
5. Applications – advantages and disadvantages
(drawbacks)
What is it?
Fluoride glasses can be formed by total
replacement of oxygen atoms in oxide glasses
by fluorine atoms
They are manufactured by melting of high purity
single element fluorides mixture
HEISENBERG’S UNCERTAINTY PRINCIPLE
E  t  
FREE ATOM  SOLID
ENERGY
E~2·10-19 eV  t~1h
E~10 eV  t~10-15s
Energy diagram
showing two atoms
encountering and
resulting in a new
molecule
DIELECTRICS
CONDUCTION BAND
FORBIDDEN BAND
(ENERGY GAP)
EMPTY
Eg > 2 eV
EF
VALENCE BAND
FULL
DOPED DIELECTRICS
CONDUCTION BAND (EMPTY)
DOPED IONS LEVELS
USED IN LASER ACTION
VALENCE BAND
FOR INSTANCE
RARE EARTH
ELEMENTS IN
GLASSES
RARE EARTH IONS IN CRYSTALS AND GLASSES
http://www.gel.ulaval.ca/~copgel/conferences/edfa1/tsld001.htm
RARE EARTH IONS IN CRYSTALS AND GLASSES
RARE EARTH IONS IN CRYSTALS AND GLASSES
RARE EARTH IONS IN CRYSTALS AND GLASSES
TABLE 1. CONVERSION FACTORS
FOR ENERGY UNITS
Unit
joule
joule
1
electron
1.602 × 10–19
volt
cm–1
1.9864 × 10–23
electron
volt
cm–1
6.24 × 1018 5.034 × 1022
1
8065.73
1.24 × 10–4
1
1240
λ nm 
E eV
10000600
λ nm 
1
E [cm ]
1240
E eV 
λ nm
10000600
1
E [cm ] 
λ [nm]
EXAMPLE : CONVERSION OF ENERGY IN JOULES TO CM-1
Given:
A HeNe laser photon has a wavelength of 632.8 nanometers
Find:
(a) Photon energy in joules
(b) Photon energy in cm–1
Solution
:
(a) find energy of HeNe laser photon in joules.
Where h=6.625´ 10-34J · sec
c=3´ 108m/sec
 =632.8nm=632.8´ 10-9m
(b) Use Table 1 to convert 3.14´ 10-19 joules to cm-1. Locate "joule" in the first row in the left hand
column. Follow this row over to the column headed "cm-1." At the intersection of the row and
column, find the conversion factor 5.034´ 1022 cm-1/joule. Multiply this factor by 3.14´ 10-19 joules
to change the energy from joules to cm-1.
The "joule" units cancel, and you get E=15,806.8cm-1
THE INTERACTION OF RADIATION WITH MATTER
X-rays
Scattering
Energy
Phototionisation
Ionisation energy
Large no.
of states
-strongly
absorbed
Ultraviolet
Visible
Infrared
Small no.
of states
-almost
transparent
Electronic
level
changes
Vibration
Microwaves
Rotation
ATOM MUST RETURN FROM EXCITED STATE TO GROUND STATE.
HOW?
SEVERAL WAYS TO RETURN TO GROUND STATE
QUANTUM YIELD OF LUMINESCENCE
SEVERAL WAYS TO RETURN TO GROUND STATE.
LIFETIMES
FLUORESCENCE VERSUS PHOSPHORESCENCE
SYMBOLS USED IN ATOMIC PHYSICS
Spin multiplicity
A state can be specified by its spin multiplicity (2S+1).
No. unpaired electrons
0
1
2
3



S
S=0
S = 1/2
S=1
S = 3/2
S0 ground state singlet
S1, S2……excited state singlets
T1, T2….…excited state triplets
Multiplicity
State
2S + 1 = 1
2S + 1 = 2
2S + 1 = 3
2S + 1 = 4
singlet
doublet
triplet
quartet
REE ABSORPTION SPECTRA IN FLUORIDE
GLASSES
Wavenumber [cm-1]
30000
10000
20000
3
5000
3
P2
3
1
P1, I6
3
5
3
P0
1
F3
F4
3
3
D2
1
G4
Absorbance
5
5
K7
5
4
5
D2
5
G6
G5
3
G4
G9/2
K15/2
F2
5
5
F5
5
300
4
Ho
I7
I6
F9/2
4
4
4
S3/2
4
I11/2
3
3
3
Er
I13/2
I9/2
F2 , F3
D2
400
5
H11/2
F7/2
F3/2
4
2
G9/2 F5/2
1
Eu
5
K 8 F3
4
F6
D0
3
1
Pr
S2 , F4
2
4
5
D1
G11/2
4
2
5
D3
5
5
H6
L6
7
3
F2
H5
3
H4
Tm
F4
G4
500
600
700
Wavelength [nm]
800
1000
2000
EACH ABSORPTION LINE CORRESPONDS TO THE
RESPECTIVE ELECTRON TRANSITION BETWEEN
TWO ENERGY LEVELS (GROUND STATE AND
EXCITED STATE)
WE ARE ABLE TO RECONSTRUCT THE ELECTRON
ENERGY STRUCTURE ON THE BASE OF
ABSORPTION SPECTRA
RECONSTRUCTED ELECTRON ENERGY LEVELS
IN FLUOROINDATE GLASSES
30000
Pr
Eu
Ho
5
25000
D4
5
G4
5
G2
5
L6
3
5
5
D3
3
P2
I
P1
3
P0
Energy [cm-1]
20000
5
D2
5
G4
5
1
D0
D2
K15/2
G9/2
4
G11/2
4
2
G5
D2
G9/2
F3/2
F5/2
4
1
4
2
H11/2
S3/2
5
S2
5
F4
4
F5
3
4
F9/2
I9/2
5
F
F
3 2
3
3
4
10000
G4
F7/2
5
15000
1
4
G6
3
5 K8
F
5 2
F3
5
D1
Tm
2
K7
5
1
3 6
Er
H4
I5
1
4
G4
I11/2
5
I6
3
H5
3
F4
F3
3
5000
0
4
3
F2
3
H6
3
H4
3
F0
3
4
3
F4
I7
F6
3
I13/2
5
5
I8
I15/2
H6
SPONTANEOUS EMISSION
THREE-LEVEL LASER (TRANSITION PROBABILITIES AND LIFETIMES)
E3
Pij = Pji
E2
P23 > P13 >> P12
2 >> 3
INVERSION
E1
N2 >> N1
STIMULATED EMISSION
Emission of Radiation
Stimulated Emission
Stimulated emission is the exact analogue of absorption. An
excited species interacts with the oscillating electric field and
gives up its energy to the incident radiation.
h
U
h
U
2h
L
L
Stimulated emission is an essential part of laser action.
LIFETIMES OF EXCITED STATES
FOUR-LEVEL LASER (Cr3+ doped ruby)
THREE-LEVEL LASER (quantum amplifier)
E3
10-8 s
E2
10-3 s
E = h· = E2 – E1
E1
OPTICAL PUMPING
Time-schedule of laser action
To amplify number of photons going through the atoms we need
more atoms in upper energy level than in lower.
Amplification or loss is just Nupper-Nlower.
Nupper > Nlower, more out than in
Nupper < Nlower, fewer out than in
PRINCIPLE OF LASER ACTION
PRINCIPLE OF LASER ACTION
NUMBER OF PHOTONS ~ 2N (N – ACTIVE ELEMENT CONTENT)
LASER RESONANCE SYSTEM
HISTORY
1974 - Marcel & Michel Poulain and Jacques
Lucas discovered first fluoride glass
(Univ. Rennes, France)
Accidentally !!!
First commercial fluoride glass – about 1990
FLUOROZIRCONATE GLASS
ZrF4-BaF2-LaF3-AlF3-NaF
Acronym - ZBLAN
FLUOROINDATE GLASS
InF3-ZnF2-BaF2-SrF2-GaF3-NaF
Acronym - IZBSGN
ADVANTAGES
1. Low phonon energy
2. Low absorption in IR range
3. Wide transmission band
4. High refraction index
Comparison of various glasses properties to those of silica
glasses
A PIECE OF PHYSICS
Phonons in a lattice
Acoustic branch-wide frequency
band
Optical branch - almost constant
frequency
THIS FREQUENCY IS MUCH LOWER IN FLUORIDE GLASSES
THAN IN SILICA GLASSES
IR light absorbtion in fluoride glasses is much lower than
in silica glasses
VIBRATIONS OF DIATOMIC CHAIN – OPTICAL PHONONS
Equation of motion (Newton’s second principle)
Disperssion relations
TRANSMISSION BAND
FLUOROINDATE GLASSES
FLUOROZIRCONATE GLASSES
SILICA
GLASSES
0
3000
6000
9000
12000
DŁUGOŚĆ FALI [nm]
Wavelength
15000
TRANSMISSION BAND – FLUOROINDATE GLASS
Wavenumber [cm-1]
4000
3000
2000
1000
Transmission[%]
100
0
3
Wavelength [m]
6
12
1824
ELECTRON ENERGY LEVELS
30000
Pr
Eu
Ho
5
25000
D4
5
G4
5
G2
5
L6
3
5
5
D3
3
P2
I
P1
3
P0
Energy [cm-1]
20000
5
D2
5
G4
5
1
D0
D2
K15/2
G9/2
4
G11/2
4
2
G5
D2
G9/2
F3/2
F5/2
4
1
4
2
H11/2
S3/2
5
S2
5
F4
4
F5
3
4
F9/2
I9/2
5
F
F
3 2
3
3
4
10000
G4
F7/2
5
15000
1
4
G6
3
5 K8
F
5 2
F3
5
D1
Tm
2
K7
5
1
3 6
Er
H4
I5
1
4
G4
I11/2
5
I6
3
H5
3
F4
F3
3
5000
0
4
3
F2
3
H6
3
H4
3
F0
3
4
3
F4
I7
F6
3
I13/2
5
5
I8
I15/2
H6
LUMINESCENCE (IZBSGN)
Ho
0.56 % mol.
EMISSION
EE[cm
[cm-1-1] ]
1200
Wavelength [nm]
1100
1000
900
800
700
Luminescence intensity [a.u.]
0.5 % mol.
5
6 % mol.
5
S2- I7
5
5
5
5
I6- I8
5
9000
5
S2- I6
5
F5- I7
10000
5
F5- I8
5
5
I5- I8
11000
5
5
I4- I8
12000
Wavenumber
13000
[cm-1]
14000
15000
EMISSION (IZBSGN)
E [cm-1]
Ho
0.5 % mol
LUMINESCENCE (IZBSGN)
Pr
EMISSION
Wavelength [nm]
Luminescence intensity [a.u.]
720
680
640
600
560
520
1
D2
P0 |
| 3
H4
3
H6
3
3
P0
|
3
P1
|
3
F4
3
1
3
3
3
P1 D2
|
|
14000
F3 H5
15000
F2
3
P1
|
3
3
P1
|
P0
|
3
H5
3
H5
3
H6
16000
17000
18000
-1
Wavenumber [cm ]
19000
EMISSION (IZBSGN)
Pr
E [cm-1]
Er
LUMINESCENCE (IZBSGN)
EMISSION
Wavelength [nm]
Luminescence intensity [a.u.]
560
4
540
520
4
S3/2- I15/2
18000 18600 19200
690
4
660
4
630
F9/2- I15/2
14400 15000 15600
870
4
840
4
S3/2- I13/2
11600
12000
Wavenumber [cm-1]
1050
4
1000
4
950
I11/2- I15/2
9600 10000 10400
EMISSION (IZBSGN)
Er
E [cm-1]
LUMINESCENCE (IZBSGN)
EMISSION
Tm + Tb
Luminescence intensity [a.u.]
1
0.5% Tm
3
D2- F4
1
 wzb. = 355nm ( D2)
1
1
1
3
1
3
D2- H4
3
G4- H5
12000
D2- H5
3
D2- F3
D2- F2
1
3
1
14000
0.5% Tm
3
G4- F4
16000
1
 wzb. = 470nm ( G4)
18000
20000
Wavenumber [cm-1]
22000
Intensywność luminescencji [j.wzgl.]
Tm
1
1% Tm + 3% Tb
3
D2- F4
(Tm)
1
 wzb. = 355nm ( D2)
(Tb)
5
1
3
G4 - F 4
5
7
D4- F5
1% Tm + 3%1 Tb
3
G4- H5
12000
(Tb)
(Tm)
(Tm)
1
7
D4- F5
5
5
D4
D
| (Tb) 4
|
7
7
F3
F4
14000
16000
18000
 wzb. = 470nm ( G4)
20000
22000
Wavenumber [cm-1]
24000
EMISSION (IZBSGN)
Tm
E [cm-1]
EMISSION (IZBSGN)
Tm - Tb
E [cm-1]
useless
LIFETIMES & QUANTUM YIELDS OF DOPED
FLUOROINDATE GLASSES
Aktywator
Dopant
Poziom
Level
3
Pr
1
Eu
Ho
5
P0
D2
D0
S2
5
4
S3/2
4
F9/2
Er
4
I11/2
1
D2
1
G4
3
H4
Tm
3
F4
Stężenie
Concentr.
[%mol]
[%mol]
Czas życia
Lifetime
[ms] [ms]
Zmierzony mm Computed
Obliczony rad
Experimental
rad
0.5
0.5
2
0.05
0.012
0.012
0.012
0.400
2
2
1
6
2
8
2
8
2
8
0.1
0.5
5
0.1
0.5
5
0.1
0.5
5
0.1
5
0.005
0.370
0.140
0.078
0.183
0.028
0.299
0.261
6.680
3.550
0.048
0.048
0.005
0.634
0.313
0.004
1.287
1.000
0.020
4.400
0.700
0.033
0.432
6.320
0.442
0.526
0.741
6.710
0.072
0.815
1.300
8.000
Wydajność
Quantum
kwant.
efficiency

 rad
=
[%]
=m
m//
rad [%]
36.4
36.4
36.4
92.6
1.2
5.9
31.7
17.6
34.8
5.3
40.3
35.2
99.6
52.9
66.7
66.7
6.9
77.8
38.4
0.5
99.0
76.9
1.5
55.0
8.8
DISADVANTAGES
(DRAWBACKS)
1. Substrates are hygroscopic (built-in OH groups result in
additional absorption band in IR range)
2. Difference of TX and Tg is low ( 100 0C)
3. Crystallization susceptibility is high
PARAMETERS OF STABILITY
Tg – glass transformation temperature
TX – crystallization temperature (beginning)
TP - crystallization temperature (peak)
T = Tx – Tg
 HRUBY PARAMETER
H = (TX – TG) / TG
 SAAD PARAMETER :
S = [(TX – TG) (TP – TX)] / TG
CHARACTERISTIC TEMPERATURES OF FLUORINDATE GLASSES
Various
in fluoride
Szkłodopants
fluoroindowe
glass Ln3+
domieszkowane
Tg [0C]
Tx [0C]
Tp [0C]
T [0C]
H
S
1 % mol PrF3
(*)
294
408
434
0.39
10.08
A
2 % mol EuF3
(**)
294
402
426
114
114
108
108
0.37
8.82
K
2 % mol EuF3
(*)
294
406
431
112
112
0.38
9.52
T
8 % mol EuF3
(*)
307
389
398
82
0.27
2.40
Y
0.5 % mol HoF3 (*)
294
410
430
116
116
0.39
7.89
W
6 % mol HoF3 (*)
306
386
399
80
0.26
3.40
A
2 % mol ErF3
(***)
305
423
457.5
118
118
0.39
13.35
T
8 % mol ErF3
(***)
310
375
382
65
0.21
1.47
O
0.5 % mol TmF3 (*)
294
409
430
115
115
0.39
8.21
R
5 % mol TmF3 (*)
300
388
394
88
0.29
1.76
(*) IZBSGN
(**) IZBS
(***) IZBSGL
GLOVE DRY PREPARATION BOX
GLOVE DRY MELTING BOX
Pr3+ doped fluoroindate glass
STRUCTURE OF FLUORIDE GLASSES
REVERSE MONTE CARLO MODELLING (RMC)
RIETVELD MODELLING
VARIATION OF GIBBS FREE ENERGY DURING
VITRIFICATION AND CRYSTALLIZATION
Overcooled liquid
liquid
glass
Stable glass
Single
crystal
Range of structural order
POULAIN & LUCAS
STRUCTURE OF
FLUOROZIRCONATE GLASS
(ZBLAN)
1974
EXAMPLE OF RMC MODELLING (NaPbM2F9)
PROJECTION OF THE RMC CUBIC BOX SHOWING THE 300
[MF6] POLYHEDRA NETWORK.
NaPbFe2F9
[MF6] octahedra are in blue; Na atoms in green
and Pb atoms in red
NaPbM2F
9
Five [MF6] polyhedra linked by edges as found
in the RMC model
EXPERIMENTAL VERIFICATION BY
NEUTRON DIFFRACTION OR
LOW ANGLE X-RAY SCATTERING
EXAMPLE
SiO2 - crystalline
SiO2 - amorphous
I coordination zone – 3 at
I coordination zone – 3 at
II coordination zone – 3 at
II coordination zone – 4 at
III coordination zone – 6 at
III coordination zone – 4 at
LEAST SQUARES FIT TO EXPERIMENTAL RESULTS
(NEUTRON DIFFRACTION AND X-RAY SCATTERING)
NaPbM2F9 : neutron data for M = Fe
LEAST SQUARES FIT TO EXPERIMENTAL RESULTS
(NEUTRON DIFFRACTION AND X-RAY SCATTERING)
NaPbM2F9 (M = Fe, V)
neutron data for M = V
LEAST SQUARES FIT TO EXPERIMENTAL RESULTS
(NEUTRON DIFFRACTION AND X-RAY SCATTERING)
NaPbM2F9 (M = Fe,
V)
X-ray data for M = Fe
REFERENCES
http://www.studsvik.uu.se/Software/RMC/mcgr.htm
http://tigger.phy.bris.ac.uk/~liqwww/links.html
http://www.cristal.org/glasses/glassvir.html
http://www.cis.tugraz.at/ptc/specmag/struct/s.htm
http://www.materials.leeds.ac.uk/Groups/Photonics/photonic.htm
http://www.gel.ulaval.ca/~copgel/conferences/edfa1/sld001.htm
http://irfibers.rutgers.edu/ir_rev_intro.html
http://www.mete.metu.edu.tr/PEOPLE/FACULTY/aydinol/gfa/sld001.htm