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惯性约束聚变激光驱动器中,熔石英透镜的紫外激光损伤问题一直是限制其负载能力提升的重要因素。对此提出了一种新的大口径光束三倍频构型方案,将三倍频晶体置于聚焦透镜之后,在基频光和倍频光的会聚过程中实现和频。大口径会聚光束的入射角度达36.35 mrad,为满足相位匹配条件,三倍频晶体采用相位匹配接受角度更大、损伤阈值更高的LBO晶体。理论分析表明,3块切割角度不同的LBO晶体拼接即可满足会聚光束相位匹配容忍角的要求。原理性实验也验证了该方案的可行性。该构型不仅能规避熔石英透镜的紫外激光辐照,提升激光驱动器的负载能力,而且能突破LBO晶体的口径受限问题。
Inertial confinement fusion laser driver, fused silica lens UV laser damage has been an important factor to limit the load capacity increase. In this regard, a new scheme of triple-frequency configuration of large-aperture beam is proposed. After the triplet-frequency crystal is placed in the focusing lens, the sum frequency is achieved during the convergence of the fundamental frequency and frequency doubling light. The incident angle of the large-aperture convergent beam reaches 36.35 mrad. To meet the phase matching condition, the triplet crystal adopts phase matching to accept LBO crystal with larger angle and higher damage threshold. Theoretical analysis shows that the splitting of three LBO crystals with different cutting angles can meet the requirement of phase angle tolerance of convergent beam. The principle experiment also verifies the feasibility of this scheme. The configuration can not only evade the ultraviolet laser irradiation of the fused silica lens, but also improve the load capacity of the laser driver, and can overcome the limitation of the caliber of the LBO crystal.