Abstract
In this paper, Ti:Sa amplifiers with crystals of the different geometries are discussed. Benefits of using this active medium for a thin disk (TD) and slab amplifiers are evaluated numerically and tested experimentally. Thermal management for amplifiers with multi-kW average power and multi-J pulse energy has been demonstrated. The presented numerical simulations revealed the existing limitations for heat extraction in TD geometry in the sub-joule energy regime for higher repetition rate operation. Geometry conversion from TD to thin-slab (TS) and cross-thin-slab (XTS) configurations significantly increases the cooling efficiency with an acceptable crystal temperature for pump average power values up to few kW with room temperature cooling, and up to tens of kW with cryogenic cooling. The abilities to attain 0.3 J output energy and a greater than 50% extraction efficiency were demonstrated with a repetition rate exceeding 10 kHz with room temperature cooling and one order more of a repetition rate with cryogenic conditions with pulsed pumping. Direct diode pumping simulated for CW regimes demonstrated 1.4 kW output power with 34% extraction efficiency using room temperature cooling and more than 10 kW and ~40% efficiency with cryogenic cooling.
Highlights
The recent achievements in the research area of ultra-high peak power laser systems allowed to reach extremely high concentration of the light energy after focusing with intensity 1022–1023 W/cm2 [1]
Thin disk (TD) geometry has been used as the laser active media in oscillators and amplifiers and has resulted in 100 kW output power with CW regimes [7] and up to several joules energy per pulse with the high repetition rate in a master oscillator–power amplifiers (MOPA) system [8]
The heat from the thin disk (TD) is extracted through the largest face of the active media, making cooling more effective and uniform compared to the conventional a-side surface heating extraction technique
Summary
The recent achievements in the research area of ultra-high peak power laser systems allowed to reach extremely high concentration of the light energy after focusing with intensity 1022–1023 W/cm2 [1]. The progressive idea of the chirped pulse amplification (CPA) [5,6] for the optical range gave an efficient way to increase energy of the pulses with extremely short duration This approach allowed to reach a very high peak power and intensity. Contrary to the relatively low YAG thermoconductivity ~11 W/(m·K) at 300 K, which requires a very thin sub-mm crystal thickness for efficient heating extraction, Ti:Sa possesses 35 W/(m·K) at 300 K and 1000 W/(m·K) at 77 K This allows further scaling of energy and power, by increasing thickness and aperture of the crystal. Ti:Sa’s larger emission cross section and crystal thickness permits to reach the saturation and efficient energy extraction only for few passes, and significantly simplify the system [8,14]
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