Liu Guowei, Wang Zhengping, Yu Pingzhang, Ren Hongkai, Sun Xun, Xu Xinguang
Opt Express. 2024 Feb 26;32(5):8122-8128. doi: 10.1364/OE.518377.
In current inertial confinement fusion (ICF) facilities, potassium dihydrogen phosphate (KHPO, KDP) type crystals are the only nonlinear optical (NLO) materials that can satisfy the aperture requirement of the ICF laser driver. Ammonium dihydrogen phosphate (NHHPO, ADP) crystal is a typical isomer of KDP crystal, with a large nonlinear optical coefficient, high ultraviolet transmittance, and large growth sizes, which is an important deep ultraviolet (UV) NLO material. In this paper, we investigated the effect of ADP temperature on its fourth-harmonic-generation (FHG) performance. When the temperature of the ADP crystal was elevated to 48.9 °C, the 90° phase-matched FHG of the 1064 nm laser was realized. Compared with the 79° phase-matched FHG at room temperature (23.0 °C), the output energy at 266 nm, conversion efficiency, angular acceptance, and laser-induced damage threshold (LIDT) increased 113%, 71%, 623%, 19.6%, respectively. It shows that elevating ADP temperature is an efficient method to improve its deep UV frequency conversion properties, which may also be available to other NLO crystals. This discovery provides a very valuable technology for the future development of UV, deep UV lasers in ICF facilities.
在当前的惯性约束聚变（ICF）设施中，磷酸二氢钾（KH₂PO₄，KDP）型晶体是唯一能够满足ICF激光驱动器孔径要求的非线性光学（NLO）材料。磷酸二氢铵（NH₄H₂PO₄，ADP）晶体是KDP晶体的典型异构体，具有大的非线性光学系数、高的紫外透过率和大的生长尺寸，是一种重要的深紫外（UV）NLO材料。在本文中，我们研究了ADP温度对其四倍频（FHG）性能的影响。当ADP晶体温度升高到48.9 °C时，实现了1064 nm激光的90°相位匹配FHG。与室温（23.0 °C）下79°相位匹配的FHG相比，266 nm处的输出能量、转换效率、角度接受度和激光诱导损伤阈值（LIDT）分别提高了113%、71%、623%、19.6%。结果表明，提高ADP温度是改善其深紫外频率转换特性的有效方法，这对其他NLO晶体也可能适用。这一发现为ICF设施中紫外、深紫外激光器的未来发展提供了一项非常有价值的技术。
