Study On Alkali Atom Assembly Absorption And Dispersion Characteristics

Alkali atoms are the most important elements which prevail in precision spectroscopy,fast and slow light,and the standard quantum information discipline.Its also shows importance in atomic spin gyroscope and sodium laser guide star,with their buildings standing on grounds of manipulating hot atom's macro quantum spin state from a universal quantum view.Moreover,alkali atoms act as gain medium for alkali vapor laser,one of most promising high energy laser candicates.Absorption and dispersion,as wide known by physicists,are just two faces of light interaction with matters,and alkali atoms are the most prominent example due to its strong D line transitions.This is just the background of the thesis,the contents are as follows:1.Based on the density matrix theory and the optical-Bloch equations,a theoretical model is set up to describe the interaction between light and atom assembly.The dispersion and absorption expressions are deduced from the model.The dispersion characteristics are simulated and analyzed with different conditions of absorption and gain,homogeneously broadening and vise versa,the equivalence between absorption and dispersion is re-discussed with Kramers-Kronig view.2.The availability of different saturated vapor pressure equations is discussed and the dipole moments of rubidium hyperfine structure are calculated by means of Clebsch-Gordan coefficients and Wigner-Eckart theory.Afterwards,the absorption and dispersion characteristics of rubidium D1 line with isotope and natural abundance considered are simulated.The agreement between quantum theory and the mathematical deriving from Kramers-Kronig relations tests the availability of Kramers Kronig relations.3.Using differential spectroscopy based on Beer-Lambert theory,a high precision absorption spectroscopy of Rb⁸⁷ atom assembly's D1 line was acquired.Through theoretical estimation and experimentally verification,an appropriate incident laser intensity of I/Isat=0.1 was adopted with taking the signal to noise ratio of detectors into account.The absorption spectroscopy of hot atom assembly indicated ²% abundance of Rb85 atoms in the cell.4.By Mach-Zehnder interferometer,D1 line dispersive characteristic of Rb⁸⁷ atom assembly was quantitatively measured.With limited experimental conditions,the measurement accuracy was as high as 10 ppm.Compared with theoretical prediction,the deviations were less than an order of magnitude.We propose a Kramers-Kronig relations based,sensitive interferometry method for alkali laser gain distribution measurement which derives from spatial dispersion information.