碘吸收激光稳频中调制信号的理论计算

Theoretical calculation of modulation signal in iodine absorption laser frequency stabilization

激光频率标准是将激光频率锁定于原子或分子的超精细能级间的跃迁频率,从而获得高精密度的激光频率输出。在激光稳频研究工作中,通常将碘分子的吸收谱线采用导数谱、FM光谱和调制转移光谱MTS(ModulationTransferSpectroscopy)进行频率的精密控制。为更好地消除吸收谱线的本底噪声,目前最好的稳频方案是采用调制转移光谱法。它具有高灵敏度、高分辨率和无多普勒背景等特点。从物理学的原理出发,分析了激光对介质的极化机理,导出介质对激光的吸收和色散作用的数学模型,用信号处理的技术从理论上推导了MTS谱线线型,分析了光谱线型的特性,讨论了提高激光频率稳定度的各种情况。

Laser frequency standard is high precision laser whose frequency is locked on the transition frequency between hyperfine energy levels of atom or molecule. Derivative spectroscopy, FM(Frequency Modulation Spectroscopy) and MTS(Modulation Transfer Spectroscopy) are often adopted to control the laser frequency with high precision and stabilization. At present time, MTS is the best method of laser frequency stabilization since spectrum background noise can be eliminated well, with high sensitivity & resolution, and without Doppler background. According physics principle, analyzing the mechanism of medium polarization in optic field, the mathematic model of absorption and dispersion effect on laser are deduced. By using technology of signal processing, spectra line-shape of MTS was obtained. Its properties are analyzed and various conditions of getting high stabilization laser are discussed.