Research Of Laser Techniques And Spectroscopy Detection For Strontium Optical Lattice Clock

The modern sciences and technology demand a much higher time and frequency precision in some fields, such as the measurements of the physical constant, navigation and astronomical observation. The strontium optical clock is one of proactive primary frequency standard, and both the frequency instability and uncertainty of which have been entered the order of 10-18, indicating a prospective possibility of being the next primary frequency standard.The work of this paper based on the platform of the strontium optical lattice clock in National Time Service Center(NTSC). The primary researches were focused on the narrow linewidth laser and the precision spectra. The works are summarized as below:1. The establish of 689 nm narrow linewidth laser. With the Pound-Drever-Hall(PDH) technique, an external cavity diode laser was locked to the resonance frequency of an ULE optical cavity, and the linewith of which is about 230 Hz measured by beating two identical system. The frequency was also measured using an optical frequency comb, turning out the linear frequency drift with the time is 0.16 Hz/s. Also, the power was amplified by an optical injection locked slave laser, and the time sequence control was designed. These results demonstrate this laser system satisfying the demanding of narrow line laser cooling of strontium atoms.2. The frequency measurement of the intercombination transition of the four natural strontium isotopes. In order to measure the intercombination transition frequency, the saturated absorption spectra are detected in spite of the extremely weak fluorescence of the low abundance isotopes. Especially for the 84 Sr, only being of abundance with 0.56%, It was the first reported result. The center frequencies of the lamb dips were measured using a fiber femtosecond laser optical frequency comb, and corrected after taking into account the main systematic errors. The final results were given out with an uncertainty and keep a good agreement with other reported results within the uncertainty. The results of this work give more confirmations of the reported results and supplemented the data of the lowest abundance isotope 84 Sr.3. The femtosecond laser optical frequency comb(FLOFC) can be used for the optical frequency measurement and optical clock, and also can be an optical frequency synthesizer which can generate arbitrary frequency laser within it covered range. But the outputting contains a giant number of modes that is extremely low power for individual mode, resulting it can not be directly used for the most of experiments. What is more, the weak power of the individual mode may limit the signal to noise ratio and the loop bandwidth of the phase locking when using the optical comb to transfer the coherence of frequency reference. This work selected and amplified a single mode from a FLOFC with a power about 10 m W and a side mode suppression about 37 d B, and obtained a satisfying narrow linewidth laser at 689 nm for the narrow line laser cooling of strontium atoms.4. The obtaining of cold strontium atoms and the detection of clock transition of the 88 Sr boson strontium. With the established narrow linewith laser, a strontium cold atom MOT below 1μK was obtained and further loaded into an one dimension optical lattice that confine the atoms into Lamb-Dicke regime. The magnetic induced clock transition spectrum of 88 Sr was acquired using an Hz level linewidth 698 nm laser. The Rabi flopping of the clock transition also be measured which can indicate the coherence of the system.