我們依過去Cs:6S1/2→8S1/2 直接雙光子躍遷的實驗經驗，認為Cs 對於雙光子躍遷對於磁場並不敏感。透過這次實驗我們發現如果是階梯式雙光子躍遷則可能對磁場非常敏感，在論文中我將由基本的原子物理解釋這樣差異。;This paper attempts to develop a offset-frequency locking technology for our laboratory, which we call pulse offset frequency locking technique. This technique can indirectly refer ordinary mode-locked lasers to cesium atomic clocks through an optical comb laser. The key is to use an optical comb laser with self-referencesystem as a frequency reference for other mode-locked lasers that cannot confirm their carrier-envelope offset frequency.
This technique is use to study direct frequency-comb spectroscopy of Cs&Rb atoms, mainly Cs:6S1/2→6P3/2→8S1/2and Rb:5S1/2→5P3/2→5D5/2stepwise two-photon transition. While Rb spectral line is one of the frequency standards suggested by BIPM. This research develops experimental techniques for building optical clocks using comb lasers and Cs&Rb mixed atomic cell.
In the past, mode-locked laser in our laboratory needs beat frequency with other stabilized single-frequency lasers to obtain the carrier envelope offset frequency. However, the absolute frequency of our stabilized single-frequency laser is unconfirmed. From past experiments in our laboratory, our senior member found that the Cs spectra had an error of 200 ~300 kHz compared with the theoretical calculation. In order to solve the defect that absolute frequency cannot be directly obtained in the experiment, I locked the mode-locked laser with pulse offset frequency locking technique, and use this laser to scan the atomic spectral lines. We confirmed the reason of 300 kHz error is Zeeman shift caused by magnetic field on atomic cell. We try to correct this error and verify the reliability of the pulse offset frequency locking technique for scanning atomic spectra.
According to experiences from Cs:6S1/2→8S1/2direct twophoton transition experiments, We think that the 6S1/2→8S1/2 two-photon transition of Cs is insensitive to magnetic fields. However, from this experiment we found that the transition may be very sensitive to magnetic fields if it is a stepped two-photon transition. In this paper I will explain the difference between the two types of two-photon transition from atomic physics.
