用于互组跃迁谱测量的窄线宽激光系统

Narrow linewidth laser system used for the intercombination transition spectrum measurement

采用Pound-Drerer-Hall稳频技术将689 nm激光锁定在高精细度超稳极低膨胀系数材料腔上,实现用于探测锶原子互组跃迁谱的窄线宽激光.利用光腔衰荡光谱技术,测量了不同阶次多横模情况下腔的精细度,并在理论上分析了平凹型Fabry-Perot腔的损耗与多横模阶次的关系.考虑了光开关延时及探测器响应时间在测量中的影响,对腔衰荡时间的实验测量值进行了修正.利用光纤飞秒光频梳测量了激光器的频率漂移,测出窄线宽激光频率稳定度的秒稳优于2.8×10-13.利用窄线宽激光在锶原子束上观测到具有高信噪比的窄线宽原子跃迁谱线,实验测得谱线的线宽为55 kHz,该窄线宽原子谱线可应用于锶原子二级冷却激光绝对频率的精确测量及锶原子互组跃迁谱的四种同位素位移测量.

We observe the intercombination transition spectrum of alkaline-earth strontium, using a stable narrow 689 nm laser which is locked to a high fineness ultralow expansion reference cavity. The finesse is measured using cavity ring down techniques in different transverse modes of the cavity. Additionally, the response time of optical switch and PD monitor are taken into consideration in the measurement. Using a fiber-based optical frequency comb, the Allan deviation calculated from the counter value of the beat frequency shows a stability of 2.8 × 10-13in a 1 s averaging time. The saturation spectrum is measured with a minimum sub-Doppler width of 55 kHz. The high resolution intercombination transition spectrum can be used for absolute frequency stabilization.