Situation of Yb YAG Thin Disk Laser for

Situation of Yb: YAG Thin Disk Laser for A 1 Ground Laser Hut Super. KEKB 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) – co • Current low temperature laser operation at A 1 laser hut – Peltier cooling plates: Controllable temperature from 23 o. C to -36 o. C – 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 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 thin disk laser 6 of 11

Solution for laser head damage Comparison between Yb: YAG, Cu. W and Cu Thermal conductivity (W/m/K) Thermal expansion coefficient (10 -6/K) Yb: YAG Cu 10 W 90 Cu 15 W 85 Copper 11 190 200 396 6. 8 6. 3 7. 0 16. 4 • Cu 15 W 85 is an excellent candidate to solve mismatch • Cu 15 W 85 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 ü Atomic level contact for different materials ü Without any residual stress ü Direct bonding without intermediate ü Proven technique Principle of ambient bonding ü Suitable to thin disk laser configuration 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 Bonding sample made by Chou Univ. 1 Laser operation by use of ambient temperature bonding components in Osaka Univ. 2 • Work together with a research group for high quality bonding (from this summer) 1. 2. 21 a-S 611 -3, The 63 Spring Annual Meeting, Tokyo, JSAP. 21 a-S 611 -2, The 63 Spring Annual Meeting, Tokyo, JSAP. Yb: YAG thin disk laser 9 of 11

Yb: YAG regenerative amplifier 8 of 11

Summary Yb: YAG regenerative amplifier 11 of 11