Bez tytulu slajdu

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FLUORIDE GLASSES MATERIALS FOR BULK LASERS AND
FIBRE OPTICAL AMLIFIERS
Michal Zelechower, Silesian University of
Technology, Katowice, Poland
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• What are fluoride glasses?
• The role of rare earth elelments
• 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
• Real structure of fluoride glasses
• Applications advantages and disadvantages
  (drawbacks)

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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
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HEISENBERGS UNCERTAINTY PRINCIPLE
FREE ATOM ? SOLID
?E210-19 eV ? ?t1h ?E10 eV ? ?t10-15s
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Energy diagram showing two atoms encountering and
resulting in a new molecule
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DIELECTRICS
EMPTY
CONDUCTION BAND
ENERGY
FORBIDDEN BAND (ENERGY GAP)
Eg gt 2 eV
EF
VALENCE BAND
FULL
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DOPED DIELECTRICS
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RARE EARTH IONS IN CRYSTALS AND GLASSES
http//www.gel.ulaval.ca/copgel/conferences/edfa1
/tsld001.htm
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RARE EARTH IONS IN CRYSTALS AND GLASSES
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RARE EARTH IONS IN CRYSTALS AND GLASSES
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RARE EARTH IONS IN CRYSTALS AND GLASSES
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THE INTERACTION OF RADIATION WITH MATTER
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ATOM MUST RETURN FROM EXCITED STATE TO GROUND
STATE. HOW?
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SEVERAL WAYS TO RETURN TO GROUND STATE
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QUANTUM YIELD OF LUMINESCENCE
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SEVERAL WAYS TO RETURN TO GROUND STATE. LIFETIMES
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FLUORESCENCE VERSUS PHOSPHORESCENCE
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SYMBOLS USED IN ATOMIC PHYSICS
Spin multiplicity A state can be specified by
its spin multiplicity (2S1). No. unpaired
electrons S Multiplicity State 0 S 0
2S 1 1 singlet 1 ? S 1/2 2S 1
2 doublet 2 ?? S 1 2S 1
3 triplet 3 ??? S 3/2 2S 1
4 quartet S0 ground state singlet S1,
S2excited state singlets T1, T2.excited
state triplets
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REE ABSORPTION SPECTRA IN FLUORIDE GLASSES
Pr
Eu
Ho
Er
Tm
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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
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RECONSTRUCTED ELECTRON ENERGY LEVELS IN
FLUOROINDATE GLASSES
Pr
Eu
Ho
Er
Tm
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SPONTANEOUS EMISSION
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THREE-LEVEL LASER (TRANSITION PROBABILITIES AND
LIFETIMES)
Pij Pji
P23 gt P13 gtgt P12
?2 gtgt ?3
INVERSION
N2 gtgt N1
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STIMULATED EMISSION
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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.
Stimulated emission is an essential part of laser
action.
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LIFETIMES OF EXCITED STATES
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FOUR-LEVEL LASER (Cr3 doped ruby)
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THREE-LEVEL LASER (quantum amplifier)
E3
10-8 s
E2
10-3 s
E h? E2 E1
E1
OPTICAL PUMPING
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Time-schedule of laser action
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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 gt Nlower, more out than in
Nupper lt Nlower, fewer out than in
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PRINCIPLE OF LASER ACTION
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PRINCIPLE OF LASER ACTION NUMBER OF PHOTONS 2N
(N ACTIVE ELEMENT CONTENT)
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LASER RESONANCE SYSTEM
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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 Ac
ronym - IZBSGN
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ADVANTAGES

• Low phonon energy
• Low absorption in IR range
• Wide transmission band
• High refraction index

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Comparison of various glasses properties to those
of silica glasses
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A PIECE OF PHYSICS
Acoustic branch-wide frequency band
Phonons in a lattice
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
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VIBRATIONS OF DIATOMIC CHAIN OPTICAL PHONONS
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Equation of motion (Newtons second principle)
Disperssion relations
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TRANSMISSION BAND
FLUOROINDATE GLASSES
FLUOROZIRCONATE GLASSES
SILICA GLASSES
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TRANSMISSION BAND FLUOROINDATE GLASS
Wavenumber cm-1
100
Transmission
0
Wavelength ?m
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ELECTRON ENERGY LEVELS
Pr
Eu
Ho
Er
Tm
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LUMINESCENCE (IZBSGN)
Ho
0.5 mol.
6 mol.
EMISSION
Wavelength nm
E cm-1
E cm-1
0.5 mol.
Luminescence intensity a.u.
6 mol.
Wavenumber cm-1
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EMISSION (IZBSGN)
E cm-1
0.5 mol
Ho
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LUMINESCENCE (IZBSGN)
Pr
EMISSION
Wavelength nm
Luminescence intensity a.u.
Wavenumber cm-1
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EMISSION (IZBSGN)
E cm-1
Pr
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LUMINESCENCE (IZBSGN)
Er
EMISSION
Wavelength nm
Luminescence intensity a.u.
Wavenumber cm-1
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EMISSION (IZBSGN)
E cm-1
Er
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LUMINESCENCE (IZBSGN)
EMISSION
Tm
Tm Tb
Luminescence intensity a.u.
Intensywnosc luminescencji j.wzgl.
Wavenumber cm-1
Wavenumber cm-1
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EMISSION (IZBSGN)
E cm-1
Tm
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EMISSION (IZBSGN)
E cm-1
Tm - Tb
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LIFETIMES QUANTUM YIELDS OF DOPED FLUOROINDATE
GLASSES
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DISADVANTAGES (DRAWBACKS)

• Substrates are hygroscopic (built-in OH groups
  result in additional absorption band in IR range)
• Difference of TX and Tg is low (? 100 0C)
• Crystallization susceptibility is high

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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

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CHARACTERISTIC TEMPERATURES OF FLUORINDATE GLASSES
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GLOVE DRY PREPARATION BOX
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GLOVE DRY MELTING BOX
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Pr3 doped fluoroindate glass
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STRUCTURE OF FLUORIDE GLASSES
REVERSE MONTE CARLO MODELLING (RMC)
RIETVELD MODELLING
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VARIATION OF GIBBS FREE ENERGY DURING
VITRIFICATION AND CRYSTALLIZATION
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POULAIN LUCAS 1974
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EXAMPLE OF RMC MODELLING (NaPbM2F9)
PROJECTION OF THE RMC CUBIC BOX SHOWING THE 300
MF6 POLYHEDRA NETWORK.
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NaPbFe2F9
MF6 octahedra are in blue Na atoms in green
and Pb atoms in red
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NaPbM2F9
Five MF6 polyhedra linked by edges as found in
the RMC model
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EXPERIMENTAL VERIFICATION BY NEUTRON DIFFRACTION
OR LOW ANGLE X-RAY SCATTERING
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EXAMPLE
SiO2 - crystalline
SiO2 - amorphous
I coordination zone 3 at II coordination zone
3 at III coordination zone 6 at
I coordination zone 3 at II coordination zone
4 at III coordination zone 4 at
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LEAST SQUARES FIT TO EXPERIMENTAL RESULTS
(NEUTRON DIFFRACTION AND X-RAY SCATTERING)
NaPbM2F9 neutron data for M Fe
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LEAST SQUARES FIT TO EXPERIMENTAL RESULTS
(NEUTRON DIFFRACTION AND X-RAY SCATTERING)
NaPbM2F9 (M Fe, V)
neutron data for M V
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LEAST SQUARES FIT TO EXPERIMENTAL RESULTS
(NEUTRON DIFFRACTION AND X-RAY SCATTERING)
NaPbM2F9 (M Fe, V)
X-ray data for M Fe
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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