Theoretical And Experimental Research For Atomic Optical Filter Based On Laser Induced Optical Anisotropy

With the rapid development of the optical information technology, laser spatial information technology such as laser communication, remote sensing and lidar attract more attention. These optical systems can not operate well due to bad SNR (signal to noise ratio) caused by broadband solar background radiation and dispersive medium. However, the SNR and the sensitivity of the optical system can be improved by using an ultra-narrow bandwidth optical filter before the receiver of the optical filter. In this dissertation, laser induced optical anistropy atomic optical filter (LIAOF) were theoretically and experimentally studied based on the reviewing of the domestic and abroad developing background for atomic optical filter. The main contents of the dissertation include the following aspects:Firstly, the theoretical model for LIAOF was given. Through the analysis of the filtering mechanism for LIAOF, the density matrix equation in the semi-classical theory was utilized to deal with the interaction between two laser fields and three-level atomic system. The system susceptibility was obtained by solving the density matrix equation in the steady state. And then the complete filter model was established with associating the filter parameters with the system susceptibility.Secondly, the filter characteristics of the excited-state Rb-LIAOF at 775.9 nm were theoretically and experimentally investigated. In order to analyze the pump process of the filter behavior, the absorption spectroscopy and saturated absorption spectroscopy for Rb D2 line were theoretically and experimentally studied, and the population dynamics of magnetic sublevels for Rb D2 line were also theoretically analyzed. The experimental transmission spectrum displayed a single peak transmission of 14.4% with 396 MHz bandwidth narrower than the Doppler width. In addition, the filter characteristics of the excited-state Rb-LIAOF at 775.9 nm versus pump intensity, pump detuning, cell temperature and cell length were detailedly researched in theory and experiment.Once again, in order to further verify the reliability and universality of the theoretical model for LIAOF, the filter characteristics of the the excited-state K-LIAOF at 694 nm and 532 nm were theoretically calculated. The simulation results were in good agreement with experimental data reported previously. Through the analysis of the simulation results, a large-scale tunable atomic optical filter scheme via dynamic Stark effect was proposed. The theory predicts that tunable ability can reach over 100 GHz, what is important for laser communication and lidar subjected to large Doppler shift.Finally, the LIAOF based on optical anisotropy induced by a coherent control field was preliminarily studied in theory. The LIAOF described above is based on optical anisotropy induced by selective optical pumping. However, the medium can also exhibit optical anisotropy experienced by the linearly polarized probe field via atomic coherent induced by a strong coherent control field. In such a mechanism, the EIT and filter characteristics of the ground-state Rb-LIAOF at 780 nm were theoretically studied.