Abstract

High brightness power lasers have been constructed for specific research activities, including electron acceleration for compact X-ray free electron lasers (XFEL) by using laser plasma acceleration (LPA) and THz wave dielectric acceleration (THz-DLA), ion (proton) acceleration for radiation therapy, and so on. On the other hand, the downsizings of high brightness power laser to achieve extreme material states in the laboratory have become “impulsing paradigm change through disruptive technologies”, such as laser ignitor, laser peening of metallic bridges, long-distance laser induced breakdown spectroscopy (LIBS), laser material processing with robot arms. Passively Q-switched compact giant pulse microchip lasers (MCL) with > MW peak power based on a short pulse width (τ) and a single axial mode are therefore very attractive for such applications [1]. Further peak power scale of MCL as well as keeping compactness is necessary for applications requiring more intense laser induced plasma. From a practical view point, a higher peak power allows a wider plasma area which results in a faster process speed such as for laser peening. However, peak power and brightness [B = E/{ τ∙(λ∙M²)²}] scale of flat-flat cavity MCL was limited by pulse width broadening and M² increase because of the degradation of beam pattern due to transverse higher-order modes [2]. As a solution, we reported unstable resonator MCL has a record peak power of 59.2 MW (E=24.1 mJ, τ=407 ps), and a brightness of 8.9 TW/(sr∙cm²) at 20 Hz (Fig. 1) [3]. For further power scaling, the thermal problem managements by the stress-free bonding with a high-thermal conductivity heat sink should be required. Newly developed an inter-layer assisted surface activated direct bonding (il-SAB) can realize it [4].

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