Experimental Studies On High Resolution Spectroscopy Of Rubidium Atom At Low Excited State

The interaction between light and atom is an important research issue in atomic and molecular physics.Improving the spectral resolution can help us to intensively study the internal structure and properties of atoms.However,at room temperature,the Doppler broadening that comes from the thermal motion of atoms in the matter obscures the physically important structures in spectra and greatly limits the spectral resolution.There are now a variety of spectroscopic techniques which employ lasers to avoid the limitations imposed by Doppler broadening,such as saturation absorption spectroscopy(SAS),electromagnetically induced transparency(EIT),double resonance optical-pumping(DROP)and optical-optical double resonance(OODR).Using these high resolution spectroscopic methods,the eigenstate energies of atoms and molecules can be determined with high precision.However,with the application of external electric and magnetic fields,the experimental data obtained by the usual EIT and DROP spectroscopy methods are quite different from theoretical calculations.We can also apply high-resolution spectroscopic methods to the EIT transient process to obtain additional dynamic properties of atoms.In this dissertation,various improved high resolution spectroscopic methods are used to study the nonlinear optical properties and Zeeman splitting spectroscopy of rubidium for transitions to low excited state in applied magnetic fields,and optical properties of transient EIT spectroscopy of rubidium for transitions to low excited state.The main research contents of the dissertation are as follows:(1)The OODR high resolution spectroscopy of 87Rb for transition 5S1/2→ 5P3/2→ 5D3/2,5/2 in magnetic fields is studied.Usually,the EIT spectrum of the 87Rb atom for transition 5S1/2→ 5P3/2→5D3/2,5/2 is accompanied by the DROP effect,which leads to the broadening and distortion of the atomic spectrum,making it very difficult to extract the structural information of the atom from the spectral lines.For the first time,we adopt the OODR method to record Zeeman-splitting spectra of 87Rb to low excited states 5D3/2 and 5D5/2 in external magnetic fields.This method can remove or reduce the state-dependent spectral broadening due to DROP effect,and the obtained spectral structures are very clear.The theoretical calculations are well in accordance with experimentally observed spectra.This method allows us to accurately study the variation of a certain transition spectral line with the magnetic field strength.(2)The high resolution far-detuning EIT spectroscopy of 87Rb for transition 5S1/2→5P3/2→5D5/2 in magnetic fields is studied.Our experimental study found that the DROP effect in the EIT spectrum of 87Rb for transition 5S1/2→5P3/2→5D5/2 can also be suppressed by the method of far detuning.By the rational utilization of the far-detuning conditions,broad background in the EIT spectrum disappears and the narrow spectral lines appear which clearly show the information of the atomic Zeeman structures,with their linewidth reduced from 20 MHz to the natural linewidth limit(6 MHz).The experimental spectra are consistent with our theoretical calculations,indicating that the far-detuning EIT spectroscopy method can well reveal the high-precision structure of atoms.(3)The transient response dynamics of 87Rb atomic vapor buffered in 8 Torr Ne gas through an EIT configured in Λ-scheme are studied.We design a sequential switch to turn on and off the coupling light and record the transient transmission spectra of probe light which is resonant to transition F=2→F’=2 of 87Rb D1 line.To account for the transient switching spectral feature,we establish the time-dependent optical Bloch equation,which introduces the transverse relaxation dephasing process of the fluorescence(longitudinal)relaxation process along with the optical absorption.The corresponding Zeeman transverse relaxation time can be extracted from the theoretical simulations that well explain the experimental observation.We also study the variation of the transverse relaxation time along with the environment(coupling beam power and cell temperature).These high resolution spectroscopy methods improved and proposed by us are universal and can be applied to other atomic and molecular spectroscopy studies.These methods are of great significance to reveal the resolved structure information of atoms and molecules and the dynamic properties of related quantum states in the external fields.