Experimental Study On Frequency Stability Of Trans Portable Ytterbium Clock Laser Using Iodine Molecular Spectrum

Atomic optical clocks with ultra-narrow optical frequency transitions of atoms or ions as reference have higher frequency stability and lower uncertainty because their transition frequencies are 4-5 orders higher than those of microwave clocks.At present,the stability or uncertainty of atomic light clocks has entered 10-18 orders of magnitude,which is two orders higher than that of cesium fountain clocks defined by international unit "second".Among them,the stability of strontium and ytterbium clocks has entered 10-19 orders of magnitude.Therefore,the International Metrology Committee has planned to use atomic light clocks instead of cesium fountain clocks to redefine the international unit second,and has developed a road map to redefine the second.In order to realize the optical clock as a recommendation standard for second definition,it is a very important step to carry out high-precision comparison measurement of various optical clocks in different research institutes by means of portable optical clocks,optical fiber links or satellite links.At present,the accuracy of satellite link alignment can only reach 10"15 magnitude,which can not meet the requirements of high-precision optical clock alignment,while the optical fiber link can not achieve cross-continental remote alignment.Therefore,the development of high-precision portable optical clock is of great significance for the development of international optical clock time-fr-equency alignment and the redefinition of seconds.At the same time,transportable optical lattice clock have wide application value in the fields of high-precision geoid measurement,detection of dark matter and gravitational waves,basic physical research and space time-frequency datum,etc.Ytterbium atomic optical lattice clock with second-order second definition qualification is a popular candidate for second-order redefinition.Based on the strategic needs of the country for portable optical clock,we have developed a portable Ytterbium atomic optical clock system.The main work of my master's degree is to realize the frequency locking system of the transportable Yb atomic optical clock cooling and pumping laser,which mainly includes the following aspects:1.A temperature control device for iodine molecule absorption cell used in saturated absorption and frequency stabilization system was designed and implemented.The temperature of iodine molecule absorption cell was accurately controlled,and the temperature fluctuation was not more than 0.1 degrees Celsius.2.The hyperfine transition spectrum of iodine molecule near 798 nm was measured by the fundamental frequency light of 399 nm laser.The iodine molecule spectrum with a line width of 102 MHz was obtained,which shows the feasibility of the experimental scheme.3.The ultrafine transition spectrum of iodine molecule at 556 nm was obtained experimentally.The linewidth of the spectrum is about 1 MHz.The frequency locking of 556 nm secondary cooling laser is realized by using the transition spectrum.The laser linewidth after locking is 195 KHz,which meets the experimental requirement of secondary cooling imprisonment.4.The ultra-fine transition spectrum of iodine molecule at 694 nm with a line width of 13 MHz was obtained experimentally.The spectrum can be used to stabilize the frequency of 1388 nm pumped back laser of Yb atomic lattice clock.