CEDAR: Vapor Filters: Developing New Measurement Capabilities for Narrowband Na Lidar

这个项目是一个为期两年的努力，以启动蒸汽过滤器的发展，用于激光雷达测量在中间层顶区域。它提出了两种不同类型的蒸汽过滤器，它们的使用将为窄带Na荧光激光雷达增加新的测量能力。首先是基于Na蒸气近共振法拉第色散的窄带通滤波器。该滤波器的有效带宽约为2 GHz，峰值传输率为85%，具有宽视场。当在弗劳恩霍夫线使用时，它可以比法布里-珀罗系统更有效地抑制天空背景光，比法布里-珀罗系统有效50倍以上，使Na温度激光雷达在白天工作变得可行。第二种是温度稳定的碘蒸气电池，用作传输过滤器。I2蒸汽电池的透光率随频率的变化在几GHz范围内变化很大。由于弹性散射和Na荧光信号发生在不同的频率，比较激光雷达在两个工作频率v2和vc下，通过和不通过I2蒸汽池的回波，将为确定温度和量化弹性散射提供足够的信息。因此，在极帽区使用具有良好特征的碘蒸气过滤器和钠温度激光雷达，可以同时监测温度分布和夜光云。

This project is a two-year effort to initiate the development of vapor filters for lidar measurements in the mesopause region. It proposes two different types of vapor filters whose use will add new measurement capabilities to the narrowband Na fluorescence lidar. First is a narrow band-pass filter based on Faraday dispersion in Na vapor near resonance. This filter has an effective bandwidth of approximately 2 GHz, 85% peak transmission, and wide field-of-view. When used at a Fraunhofer line, it can reject sky background light more effectively than a Fabry-Perot system by more than a factor of 50, making the daytime operation of the Na temperature lidar practical. Second is a temperature stabilized iodine vapor cell to be used as a transmission filter. The transmittance of the I2 vapor cell as a function of frequency varies considerably within a few GHz. Since elastically scattered and Na fluorescence signals occur at different frequencies, a comparison of lidar returns at the two operating frequencies, v2 and vc, with and without passing through the I2 vapor cell will provide enough information for the determination of temperature and quantification of elastic scattering. Therefore, the use of a well characterized iodine vapor filter with a Na temperature lidar in the polar cap region will allow simultaneous monitoring of temperature profiles and noctilucent clouds.