Experimental Research On All-optical Trapping Of The⁴⁰ca⁺

Trapping atoms and ions chronically and stably,and isolating them from the environment is essential for the research and improvement of the precision measurement physics.For several decades,this has been achieved by trapping ions with radio-frequency fields and atoms with optical fields.With the development of ion trap and laser cooling technology,ion optical frequency standards based on the single ion trapped in radio-frequency fields have also been rapidly developed.However,the radio-frequency fields will inevitably introduce micromotion,which contributes greatly to the systematic frequency shifts of optical frequency standards,and it requires a generic solution to the elimination of micromotion.In 2010,the T.Schaetz group from Germany demonstrated the first all-optical trapping of single ²⁴Mg⁺ion by interaction with dipole laser fields and DC electric fields without any radio-frequency fields.This can be seen as a starting point of combining the advantages of optical trapping and ions for optical frequency standards and is also significant to the development of ion optical frequency standards.Although the laser field will cause frequency shifts to the spectrum of the ion,by selecting the laser at a specific wavelength,which means the "magic wavelength",the frequency shifts caused by the laser field to the clock transition of the ion's optical frequency standards can be greatly decreased.Therefore,the frequency shift effects caused by the laser field on the ion's optical frequency standards can be avoided.Our group is also committed to the research of ⁴⁰Ca⁺all-optical trapping in order to promote the development of ⁴⁰Ca⁺ ion optical frequency standards.The experimental research progress of all-optical trapping of ⁴⁰Ca⁺ during my doctoral period is as follows:1.The experiment system has been built for the ⁴⁰Ca⁺ all-optical trapping,including:the establishment and improvement of the blade-shape linear ion trap;the setup of a vacuum system with background gas pressure of P=3×10-9 Pa;the design and optimization of a radio-frequency system which realized the ion trapping at low frequency of ?=2?×1.319 MHz;and the establishment of the laser system including pulse ablation laser,cooling laser,detecting laser and dipole trapping laser.2.The realization of long-term stable trapping of a single ⁴⁰Ca⁺ion in the radio-frequency fields:using the pulse laser ablation method to accurately generate and load a single ⁴⁰Ca⁺ion;evaluating the trapping ability of the radio-frequency fields by measuring the secular motion frequency and ion temperature;optimizing the excess micromotion and restraining the stray electric field shifts of the ion.The single cooled ⁴⁰Ca⁺ion could stay more than 1 day in the radio-frequency fields.3.The far-detuned magic wavelength in the infrared spectrum of the clock transition of the ⁴⁰Ca⁺optical frequency standard has been measured and the attempt to implement the ⁴⁰Ca⁺ion all-optical trapping's exploratory experiment by using 397 nm laser as the dipole laser has been done:establishing the dipole trapping laser,measuring and optimizing the beam waist of the dipole laser;measuring the AC-Stark shifts caused by the dipole laser,and estimating the trapping depth of the dipole trap potential;calculating the heating rate of the dipole laser,and the optimization and improvement plan for the ⁴⁰Ca⁺ion all-optical trapping experiment has been proposed.