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

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

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

Low temperature Yb:YAG thin disk laser co 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

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

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

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

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

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

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

Summary Yb:YAG regenerative amplifier 11 of 11