Study Of Sub-Hertz Linewidth Laser And Theoretical Study Of Atom Coherent Effect In Sr System

Up to now, the best 87Sr optical lattice clock constructed by the research team of JILA has a fractional frequency inaccuracy of 1.0×10-16, which is much better than that of the present primary frequency standard based on Cs atomic fountain clock. To detect the frequency of optical lattice clock, we must have a laser beam with sub-Hertz linewidth. Therefore, the research on improving the technique of realizing sub-Hertz linewidth laser at 698nm becomes a key point of optical lattice clock. Besides, it is innovation for finding a better way to narrow the linewidth of 689nm laser which being used in the second stage cooling.In this thesis, the main work and result we have accomplished are shown as follows.First, we used frequency stabilization method of Pound-Drever-Hall radio-frequency sideband to narrow the linewidth of 698nm laser. We have achieved about 20kHz linewidth after first frequency stabilization stage, by using a pre-stable cavity as reference. Furthermore, we detailed constructing and debugging of the ultra-stable cavity.Second, we calculate the velocity distribution of atomic beam and the radius of cold atom optical molasses.At last, based on first-stage cooling , we investigated theoretically the EIT(Electromagnetically Induced Transparency) effect and Kerr nonlinear effect in Sr atomic system. This result builds theoretical basis for frequency stabilization of 689nm laser and probing frequency signal of 88Sr bosonic optics clock by using EIT effect.