We have demonstrated two-photon spectroscopy in a power-enhanced cavity of helium \(2^{3}S_{1}\)–\(8^{3}D_{1,2,3}\) transitions in a radio frequency (RF)-discharged vapor cell with a compact laser system at 544 nm. An external-cavity diode laser at 1088 nm was constructed to seed a Ytterbium-doped fiber amplifier. By employing a MgO:PPLN crystal, we have successfully doubled the laser frequency of the fiber amplifier output, generating laser power exceeding 1.2 W at 544 nm. The normalized doubling efficiency was measured to be \(0.78 \%/cm\cdot {}W\). The optical power within the power-enhanced cavity was 11.8 W. Notably, the \(2^3S_1\)–\(8^3D_{1,2,3}\)transitions were observed for the first time. Subsequently, we have investigated the pressure shift and AC stark effect of the spectra. These results pave the way for precision measurement of the transition frequencies and will provide stringent test for QED atomic calculations.

我们已经在射电中的氦功率增强腔 \(2^{3}S_{1}\)–\(8^{3}D_{1,2,3}\) 跃迁中演示了双光子光谱具有 544 nm 紧凑型激光系统的频率 (RF) 放电蒸汽室。构建了 1088 nm 的外腔二极管激光器来为掺镱光纤放大器提供种子。通过采用 MgO:PPLN 晶体，我们成功地将光纤放大器输出的激光频率加倍，在 544 nm 处产生超过 1.2 W 的激光功率。标准化倍增效率经测量为\(0.78\%/cm\cdot {}W\)。功率增强腔内的光功率为11.8 W。值得注意的是，首次观察到\(2^3S_1\)–\(8^3D_{1,2,3}\)跃迁。随后，我们研究了光谱的压力变化和交流斯塔克效应。这些结果为精确测量过渡频率铺平了道路，并将为 QED 原子计算提供严格的测试。