Flux growth and laser operation of highly Yb 3+ -doped cubic Gd 2 O 3 laser crystals M. Velázquez, Ph. Veber, G. Buşe, E. Véron, D. Rytz, F. Druon, Ph. Goldner, P. Aschehoug, S. Janicot, S. Péchev, O. Viraphong, M. Abdou-Ahmed, Th. Graf and P. Georges
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Flux growth and laser operation of highly Yb3+-doped cubic Gd2O3 laser crystals
M. Velázquez, Ph. Veber, G. Buşe, E. Véron, D. Rytz, F. Druon, Ph. Goldner, P. Aschehoug, S.
Janicot, S. Péchev, O. Viraphong, M. Abdou-Ahmed, Th. Graf and P. Georges
Scintillation materials Eyesafe telecommunications lasers (Y2O3:Tm3+) Yb3+:Lu2O3 and LuScO3-based high-power and/or sub-100 fs pulse lasers Visible phosphors and red solid state lasers (Y2O3:Eu3+) Upconverter materials for 3rd generation photovoltaïc cell, upconversion lasers (Y2O3:Er3+, Gd2O3:Tm3+)
Rare Earth SesquiOxides siNgle crystAl growTh by the flux mEthod
MRS Bulletin issue emphasizing the two main
challenges of today’s crystal growth :
production of well-established crystalline materials with
improved quality and larger size at a lower cost ;
bulk growth of new categories of materials with extreme
thermodynamic characteristics.
Yb3+:Lu2O3 and LuScO3-based high-power and/or sub-100 fs pulse lasers
Yb:Lu2O3 more promising than Yb:YAG for high-power systems diode-pumped at 976 nm (with M21.2)
Evolution of the average power of mode-locked thin-disk lasers based on Yb:YAG and Yb:Lu2O3 (Baer et al., Opt. Lett., 2010)
Yb3+:Lu2O3 and LuScO3-based high-power and/or sub-100 fs pulse lasers (2)
Average power of mode-locked TDLs versus pulse duration
(Saraceno et al., Appl. Phys. B, 2012 Ricaud et al., Opt. Lett., 2012)
CW multimode laser performance of a Lu2O3:Yb3+ (5 at.%) : 670 W, M220,
e=250 m/=7 mm (Weichelt et al., Laser Phys. Lett., 2011)
CALGO:Yb3+
Damaged Yb:LuScO3 disk (e=250 m/=6-7 mm) in the pumped area marked with the white circle Need for better quality and easily available Yb:Lu2O3 and Yb:LuScO3 single crystals
Yb3+:Lu2O3 and LuScO3-based high-power and/or sub-100 fs pulse lasers (3)
high thermal conductivity : ~10 to 13 W.m-1.K-1 at RT in Lu2O3:Yb3+ (3.6 W.m-
1.K-1 in LuScO3:Yb3+) low population inversion threshold dependency on temperature low fluence threshold emission bandwidths broader than that of YAG:Yb3+ crystals (12 nm in Lu2O3:Yb3+, 22 nm in LuScO3:Yb3+) absorption cross section of Lu2O3:Yb3+ crystals four times higher than that of YAG:Yb3+ crystals exp~1 ms, optimal for both energy storage and Q-switching avoidance
Extreme thermodynamic conditions for crystal growth of RESO
high melting point : ~2400 0C (Sm(Y2O3)=4.1 R) expensive and soluble Re crucibles, the stability of which requires an H2-containing gas flow at ~2400 0C rich polymorphism (Adachi et al., Chem. Rev., 98 (1998) 1479-1514)
HEX P32/m
MONO C2/m
CUB Ia-3
CUB Im3m
HEX P63/mmc
Hot topic in crystal growth
A new solvent for a simple flux growth furnace
crystallization temperature ~TM/2 cubic phase stability domain directly reached isotropic thermal, thermomechanical and thermooptical behaviours higher thermal conductivity, higher liquid surface tension, lower vapour pressure crystal growth in air Yb3+ stabilization without post-growth thermal treatment annealing neither heavy metal, hydroxyl groups nor corrosive species in the solvent
New flux in Gd2O3-B2O3-Li2O system : Li6Gd(BO3)3
A new solvent for a simple flux growth furnace (2)
"Method for preparing single-crystal cubic sesquioxides and uses thereof“, Veber et al., PCT Int. Appl. WO 2011/055075 A1, 12/05/2011, PCT n° FR 2010052355.
From 2010 to 2013 : useful V40
Rare Earth SesquiOxides siNgle crystAl growTh by the flux mEthod
Section=2.654.35 mm2
Thickness=1.2 mm
Gd2O3:Yb3+
Clear crystals Section > 5 5 mm2
Thickness > 1. 5 mm
Section=2.654.35 mm2
Thickness=1.2 mm
Powder X-ray diffraction (XRD) characterization
Two-phase Le Bail full pattern matching of Yb3+:Gd2O3 (Ia-3, a=10.7847 Å, Rwp=27.7, 2=2.085) shows the presence of Li6Gd(BO3)3 inclusions
Yb3+:Y2O3
low OH- content, ~2,2.1021 cm-3
Yb3+:Lu2O3 and Yb3+:Gd2O3
virtually OH--free
FT IR spectra
S. Hraïech, PhD thesis, University Claude Bernard Lyon 1 (2007)
Veber et al. Crystengcomm, 13 (16) (2011) 5220-5225
Absorption and stimulated emission cross section spectra
simple energy level diagram of Yb3+ ions (=1 ; no ESA, no down-conversion cross-relaxation, no up-conversion) large crystal field splitting of the ground state manifold (900 cm-1 ; quasi-four level laser operation) large absorption cross section at ZPL (use of thinner disks) and low absorption cross section at L highest emission peak cross section on the 53 transition
e(Gd2O3)=670 µm e(Lu2O3)=590 µm
Non radiative relaxation mechanisms
...
111
?
1111111
1exp
'
nsdislocatioYb
TmYbErYbcoop
YbYbVYbOHphmrad
iem
OYb
n
self-trapping ~14.4%
m-ph min ~104 s
~0 (growth in air between 1250 and 1100 °C)
AR WNR E=p·ħM
Energy-gap law at fixed T
Mphm pCEW exp
2S’+1L’J’
2S+1LJ
S. Hraïech, PhD thesis, University Claude Bernard Lyon 1 (2007)
OH-~15 ms
C. K. Jørgensen, J. Phys.,
C7, S n° 12, t 48, (1987), 447-450
Transmission measurements performed over Lu2O3:Yb3+ and Gd2O3:Yb3+ crystals
No Yb2+ ions absorption bands at 480, 520 and 600 nm (V. Peters, PhD thesis, University of Hamburg (2001), Germany)
Absorption coefficient measurements performed over Sc2O3:Yb3+ and Lu2O3:Yb3+ crystals
Yb2+ ions absorption bands at 480, 520 and 600 nm
(V. Peters, PhD thesis, University of Hamburg (2001), Germany)
Cooperative emission
=exp/2
Non radiative relaxation mechanisms (2)
...11?
11111exp
nsdislocatioYbTmYbErYbcoop
YbYbrad
Yb-Er and Yb-Tm ETUs
[Er3+],[Tm3+] ~ 1016 cm-3
1
1
'''
dIII ememcoop
YbYb
480 nm
~660 nm
~550 nm
~800 nm
500 nm
[Nd3+] ~ 1016 cm-3
[Dy3+],[Fe3+] ~ 1017 cm-3
Anti-Stokes emission spectra in Gd2O3:Yb3+
Typical AS emissions from Er3+ (4S3/2,4F9/2) and Tm3+ (1G4) ions in the visible range
and Yb3+-pairs cooperative emission
RT AS fluorescence transients from levels 4S3/2 of Er3+ and 1G4 of Tm3+ ions
tWtW risedec eetI
Buisson and Vial, J. Phys., L42 (1981) 115-118
In Gd2O3:Yb3+ single crystals, rise and average decay times on the order of a few hundreds of s ;
At high excitation powers, such ETU processes are likely to deplete the laser emitting level and to increase the head load in the crystals under laser operation.
Examples of cavities in V and I shape, diode pumped and qcw Ti:Sa pumped and associated profiles, uncoated and uncooled Gd1.72Yb0.28O3 crystal