1. Situation of Yb:YAG Thin Disk Laser for A1 Ground Laser Hut
SuperKEKB Injector Laser RF Gun Workshop
Rui　Zhang
ACCL Division V, RF-Gun Group
Jun 10, 2016

2. Outline Low temperature Yb:YAG thin disk laser
Preparatory work and results
Problems
Solution and next step work
Novel bonding method for thin disk laser head
Background
Experimental setup introduction
Yb:YAG regenerative amplifier
Ring cavity
Cryogenic experiment
Summary
Yb:YAG thin disk laser 2 of 11

3. Low temperature Yb:YAG thin disk laser
Low temperature laser operation feasibility analysis
Available high gain is possible
Low amplified spontaneous emission (ASE)
Simpler and more stable (compare with cryogenic laser)
Current low temperature laser operation at A1 laser hut co
Peltier cooling plates: Controllable temperature from 23 oC to -36 oC
Small vacuum chamber
Home made laser soldering laser head
Yb:YAG thin disk laser 3 of 11

4. Low temperature Yb:YAG thin disk laserco
Gain test for different temperature and wavelength
Home made tunable seed laser
Face pump and seed laser edge injection
Face pump and edge injection
Yb:YAG thin disk laser 4 of 11

5. Low temperature Yb:YAG thin disk laser at different temperature
Amplification factor against wavelength
at different temperature
Yb:YAG thin disk laser 5 of 11

6. Problems for low temperature Yb:YAG thin disk laser
Damage of soldering thin disk laser head
Bigger temperature gap for low temperature laser operation
Serious residual stress introduced by soldering
Thermal expansion mismatch between coper and Yb:YAG
Yb:YAG thin disk laser 6 of 11

7. Solution for laser head damage
Comparison between Yb:YAG, CuW and Cu
Yb:YAG
Cu10W90
Cu15W85
Copper
Thermal conductivity (W/m/K) 11
190
200
396
Thermal expansion coefficient (10-6/K)
6.8
6.3
7.0
16.4
Cu15W85 is an excellent candidate to solve mismatch
Cu15W85 heatsinks are preparing and will be tested recently
Yb:YAG thin disk laser 7 of 11

8. Novel bonding method for thin disk laser head
Residual stress introduced by soldering is unavoidable (heating)
Ambient temperature bonding is suggested
Atomic level contact for different materials
Without any residual stress
Direct bonding without intermediate
Proven technique
Suitable to thin disk laser configuration
Principle of ambient bonding
Yb:YAG thin disk laser 8 of 11

9. Novel bonding method for thin disk laser head
Ambient bonding technique has attracted attention all over the world
Work together with a research group for high quality bonding (from this summer)
Bonding sample made by Chou Univ.1
Laser operation by use of ambient temperature bonding components in Osaka Univ.2
21a-S611-3, The 63 Spring Annual Meeting, Tokyo, JSAP.
21a-S611-2, The 63 Spring Annual Meeting, Tokyo, JSAP.
Yb:YAG thin disk laser 9 of 11

10. Yb:YAG regenerative amplifier
Yb:YAG regenerative amplifier 8 of 11

11. Summary
Yb:YAG regenerative amplifier 11 of 11