瓦级319 nm单频连续紫外激光的实现及铯原子单光子Rydberg激发

Realization of a watt-level 319-nm single-frequency CW ultraviolet laser and its application in single-photon Rydberg excitation of cesium atoms

结合光纤激光器、光纤放大器和非线性光学高效频率转换技术及准位相匹配材料,服务于原子物理领域铯原子单光子跃迁里德堡激发的实际需求,研究并掌握了产生318.6nm波长连续单频紫外激光的关键技术。采用1560.5nm与1076.9nm连续激光先通过单次穿过PPLN非线性晶体和频,再经腔增强谐振倍频过程高效地产生了输出功率大于2W的318.6nm紫外激光,半小时内,光功率的方均根起伏优于0.87%。采用电子学边带锁频方案,实现了整个紫外激光系统在保持相对于高精细度超稳腔锁定条件下较大范围连续调谐,其连续调谐范围大于4GHz,残余频率起伏约16kHz。采用本文研制的高功率窄线宽可调谐318.6nm紫外激光系统,在铯热原子气室中实现了6S1/2→nP3/2(n=70~100)的单光子跃迁里德堡激发,并对相关现象作了相关的理论分析与研究。采用纯光学探测方案观察到了318.6nm紫外激光对磁光阱中铯冷原子系综的单光子跃迁里德堡激发。

In order to meet the demand for single-photon Rydberg excitation of cesium atoms in the field of atomic physics,we investigated the key technolgies of single-frequency continuous wave(CW)tunable ultraviolet(UV)laser at 318.6 nm.Combining the fiber lasers,fiber amplifiers and the nonlinear crystals,we achieved 318.6 nm UV laser over 2 Watt output with cavity-enhanced second-harmonic generation following the sum-frequency generation of two infrared lasers at 1 560.5 nm and 1 076.9 nm in PPLN crystal.The typical root-mean-square fluctuation of UV laser power was less than 0.87%within 30 minutes.The electronic side-band locking scheme based on a temperature controlled hyper-fine ultra-stable ultra-low-expansion cavity placed in an ultra-high vacuum chamber was used to achieve the continuously tuning of UV laser in a wide range while still keeping it locked.The continuously tunable range was larger than 4 GHz and the residual frequency fluctuation of UV laser was about 16 kHz.We employed this high-power single-frequency continuously tunable UV laser system for the direct 6S 1/2→n P 3/2(n=70-100)Rydberg excitation of cesium atoms with atomic vapor cells in experiments.After that,relevant theoretical analysis and research have been done.With a magneto-optical trapped cesium atomic ensemble,single-photon Rydberg excitation using the UV laser system was achieved with a pure optical detection scheme.