Martin Ostermeyer,1
Damien Mudge,2
Peter J. Veitch,2
and Jesper Munch2
1M. Ostermeyer (oster@rz.uni-potsdam.de) is with the Institute of Physics, University of Potsdam, 14669 Potsdam, Germany.
2D. Mudge, P. J. Veitch (peter.veitch@adelaide.edu.au), and J. Munch are with the Department of Physics, The University of Adelaide, Adelaide, South Australia 5005, Australia.
Martin Ostermeyer, Damien Mudge, Peter J. Veitch, and Jesper Munch, "Thermally induced birefringence in Nd:YAG slab lasers," Appl. Opt. 45, 5368-5376 (2006)
We study thermally induced birefringence in crystalline Nd:YAG
zigzag slab lasers and the associated depolarization losses. The optimum crystallographic
orientation of the zigzag slab within the Nd:YAG boule and photoelastic effects in
crystalline Nd:YAG slabs are briefly discussed. The depolarization is evaluated using the
temperature and stress distributions, calculated using a finite element model, for
realistically pumped and cooled slabs of finite dimensions. Jones matrices are then used to
calculate the depolarization of the zigzag laser mode. We compare the predictions with
measurements of depolarization, and suggest useful criteria for the design of the gain
media for such lasers.
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Maximum Temperature and Stresses for Two Infinitely Long, Optimum Cut Angle, Uniformly Pumped and Face-Cooled Slabsa
Slab height (h)
Tmax [K]
σxx,max [Mpa]
σyy,max [Mpa]
σxy,max [Mpa]
43 mm
431
130
16.4
13.3
4.3 mm
431
146
108
28
The slabs have heights of 4.3 and 43 mm. The width is w = 3 mm and the pump density is 672 MW∕m3. σxz = 0 and σyz = 0 as expected.
Table 2
Maximum Stress Levels for Slabs with Different Pump and Cooling Heights, for slab h = 4.3 mm and w = 3.0 mma
Slab
Pump profile
wcool [mm]
wpump [mm]
σxx,max [MPa]
σxy,max [MPa]
T [%]
gw11
Gaussian
1.4
1.4
144
22.6
98.5
gw22
Gaussian
2
2
128
20.7
98.5
gw33
Gaussian
3
3
109
17.7
91.5
The model assumes an incident pump power of 500 W, with 354 W being absorbed in the single pass resulting in 85 W of heating (due to the quantum defect of Nd:YAG). wcool denotes the height of the water channel, and wpump is the diameter of the Gaussian pump profile in the vertical (x) direction [see Fig. 4(b)]. T denotes the integrated transmission of a top-hat beam with diameter wpump passing through the zigzag slab located between parallel polarizers.
Table 3
Maximum Stresses for Slabs (h = 4.3 mm and h = 8.6 mm) with Different Pump and Cooling Geometries Using Top-Hat (uw) and Gaussian (gw) Pump Profilesa
Slab
Pump profile
h [mm]
wcool [mm]
wpump [mm]
σxx,max [MPa]
σxy,max [MPa]
T [%]
uw22
Top hat
4.3
2
2
122
20.2
98
gw22
Gaussian
4.3
2
2
128
20.7
98.5
uw66
Top hat
8.6
6.0
6.0
144
22.6
99
gw66
Gaussian
8.6
6.0
6.0
109
17.7
90
The model assumes an incident pump power of 500 W, with 354 W being absorbed in the single pass resulting in 85 W of heating (due to the quantum defect of Nd:YAG). h the height of the crystal, wcool denotes the height of the water channel, and wpump is the diameter of the pump profile in the vertical (x) direction [see Fig. 4(b)]. T denotes the integrated transmission of a polarized top-hat beam with diameter wpump passing through the zigzag slab located between parallel polarizers.
Table 4
Dimensions of the Side-Pumped, Side-Cooled Zigzag CPFS Slab Used in the Experiment
Pump profile
L [mm]
Lp [mm]
h [mm]
w [mm]
wcool [mm]
wpump [mm]
Cut angle φ
Gaussian
32.9
22
4.3
3.0
2.0
2.0
0°
Tables (4)
Table 1
Maximum Temperature and Stresses for Two Infinitely Long, Optimum Cut Angle, Uniformly Pumped and Face-Cooled Slabsa
Slab height (h)
Tmax [K]
σxx,max [Mpa]
σyy,max [Mpa]
σxy,max [Mpa]
43 mm
431
130
16.4
13.3
4.3 mm
431
146
108
28
The slabs have heights of 4.3 and 43 mm. The width is w = 3 mm and the pump density is 672 MW∕m3. σxz = 0 and σyz = 0 as expected.
Table 2
Maximum Stress Levels for Slabs with Different Pump and Cooling Heights, for slab h = 4.3 mm and w = 3.0 mma
Slab
Pump profile
wcool [mm]
wpump [mm]
σxx,max [MPa]
σxy,max [MPa]
T [%]
gw11
Gaussian
1.4
1.4
144
22.6
98.5
gw22
Gaussian
2
2
128
20.7
98.5
gw33
Gaussian
3
3
109
17.7
91.5
The model assumes an incident pump power of 500 W, with 354 W being absorbed in the single pass resulting in 85 W of heating (due to the quantum defect of Nd:YAG). wcool denotes the height of the water channel, and wpump is the diameter of the Gaussian pump profile in the vertical (x) direction [see Fig. 4(b)]. T denotes the integrated transmission of a top-hat beam with diameter wpump passing through the zigzag slab located between parallel polarizers.
Table 3
Maximum Stresses for Slabs (h = 4.3 mm and h = 8.6 mm) with Different Pump and Cooling Geometries Using Top-Hat (uw) and Gaussian (gw) Pump Profilesa
Slab
Pump profile
h [mm]
wcool [mm]
wpump [mm]
σxx,max [MPa]
σxy,max [MPa]
T [%]
uw22
Top hat
4.3
2
2
122
20.2
98
gw22
Gaussian
4.3
2
2
128
20.7
98.5
uw66
Top hat
8.6
6.0
6.0
144
22.6
99
gw66
Gaussian
8.6
6.0
6.0
109
17.7
90
The model assumes an incident pump power of 500 W, with 354 W being absorbed in the single pass resulting in 85 W of heating (due to the quantum defect of Nd:YAG). h the height of the crystal, wcool denotes the height of the water channel, and wpump is the diameter of the pump profile in the vertical (x) direction [see Fig. 4(b)]. T denotes the integrated transmission of a polarized top-hat beam with diameter wpump passing through the zigzag slab located between parallel polarizers.
Table 4
Dimensions of the Side-Pumped, Side-Cooled Zigzag CPFS Slab Used in the Experiment