Atomic Frequency Discriminator And Its Application In Solar Observation

The atomic frequency discriminator (AFD) is of ultra narrow bandwidth optical frequency discriminator with stable transmission function and is employed in various photoelectric systems. The solar observation based on AFD offers high spectral resolution raw data for the research and application of solar physics and space weather. In this dissertation, the AFD and its applications in solar observation were reported.With help of software which was programmed to simulate the transmission function of AFD and experimental test, some AFDs were developed for high spectral resolution solar observation. A compact twin Faraday AFD was proposed and demonstrated to overcome the polarization loss and improve the transmission for the naturally polarized light. For the purpose of observing solar atmosphere at two or more heights with one Fraunhofer line, a four-peak potassium AFD was developed under the configuration of perpendicular magnetic field. And a Zeeman AFD was developed also to select two peaks of four.The sodium and potassium two-peak Faraday AFD and Zeeman AFD were designed to ob-serve the solar Dopplergrams and magnetograms. The two-peak Faraday AFD has two peaks, named blue peak and red peak, and the Zeeman AFD was employed to select the blue or red peak of the two-peak Faraday AFD. Therefore, a frequency discriminator unit was constructed with a two-peak Faraday AFD followed by the Zeeman AFD. The AFD and optical interference fre-quency discriminator were used simultaneously to improve the tune capabilities. An etalon was employed to select the blue or red peak of the two-peak Faraday AFD. The combined frequency discriminator unit combined by a two-peak Faraday AFD and an etalon is of not only stable with ultra narrow pass band but also of tunable.Two high spectral resolution solar observation systems were developed in our laboratory. One of them is based on the two-peak Faraday AFD followed a Zeeman AFD. The other one is based on the two-peak Faraday AFD followed an etalon. The preliminary image of solar rotation was obtained with our solar observation systems. And the solar velocity field was resolved from the image of solar rotation. Then the noise and spectral interference from earth’s atmosphere was analyzed for ground-based high spectral resolution solar observation.