Research And Application Of All-solid-state Tuning-free Laser Source For Ozone Differential Absorption Lidar

Ozone is one of the most important gas components in the Earth’s atmosphere.Stratospheric ozone serves as an umbrella for lives on Earth.The ozone of high concentration absorbs most of the ultraviolet rays in the sun to prevent damage to the planet’s lives.The reduction of stratospheric ozone concentration,especially the discovery of the Antarctic ozone hole,has made stratospheric ozone the focus of attention of scientists and the public worldwide,and a large number of research results have been published around this issue.Compared with the protective effects of stratospheric ozone on the earth’s organisms,tropospheric ozone is one of the greenhouse gases and pollutant which is harmful to human health and plant growth,and can even destroy ecosystems and affect global climate change.Regional tropospheric ozone pollution incidents have occurred in many countries around the world,and China’s tropospheric ozone pollution problem is also very serious.With the rapid development of the urban economy,the air pollution in China’s large cities and urban agglomerations such as the Beijing-Tianjin-Hebei region and the Yangtze River Delta region has become more serious,and tropospheric ozone pollution has occurred frequently.In order to study the distribution of tropospheric ozone concentration and analysis of development and evolution,and to control emissions,long-term and regional monitoring is required.The differential absorption lidar can actively and quickly obtain the spatial and temporal distribution characteristics of atmospheric pollution gas concentration,which is very suitable for ozone concentration monitoring.In order to obtain the temporal and spatial distribution characteristics of tropospheric ozone in the region and analyze its development and change laws,observations at many geographic locations are needed.Therefore,there is a need for an unattended reliable system that can flexibly perform ground-based or movable observations.One of the key techniques of research in this system is a stable and reliable laser source.In the current research on the laser source of differential absorption lidar around the world,researchers usually use gas Raman,dye laser,and optical parametric oscillation(OPO)for obtaining emitting laser beams.The technology are applied to the lidar laser source system,but the light-to-light conversion efficiency,long-term operation stability,practical operation convenience,and maintainability are still insufficient.This article will introduce a compact and movable ozone differential absorption lidar based on an all-solid-state tuning-free laser source for observation of the temporal and spatial distribution of tropospheric ozone.In this paper,This paper presents the overall design scheme of the ozone differential absorption lidar system based on the all-solid-state tuning-free laser source.For the first time,the solid-state Raman technique is used in an ozone differential absorption lidar system based on an all-solid-state tuning-free laser source.First of all,the solid stimulated Raman technology,which is the key technology of ozone differential absorption lidar,is studied in detail.The lidar laser source requirements are introduced and the common types of solid Raman media and solid Raman lasers are described.A SrWO4 crystal and an external cavity Raman laser structure were used for the solid Raman media and Raman lasers suitable for this structure.The laser rate equation was used to numerically optimize the external cavity Raman laser and a set of external cavity Raman laser device was built for experimental demonstration.The spectrum,pulse width,beam profile,and output power characteristics of the Stokes beam output are analyzed.The results show that the solid-state Raman technique is suitable for ozone differential absorption lidar light source system.The 560nm first-order Stokes light of 3.3mJ and the 590nm second-order Stokes light of 2.9mJ were obtained respectively.The light-to-light conversion efficiency reached nearly 70%;the pulse width compression phenomenon in the simulation was confirmed;the power was stable during the test time,the value was 0.6%,meeting the needs of engineering use.Due to its characteristics of all-solid-state and tuning-free,while greatly improving the stability of the lidar,it also achieves the advantages of compactness and mobility.The continuous unattended observation by the customer reduces the complexity of maintenance work and makes it flexibly applied to ground-based or mobile observation.This article uses the ozone differential absorption lidar system based on the solid-state Raman technology to carry out ground-based observation and demonstration experiments.The spatial resolution of 75m and the temporal resolution of 1min are obtained,and the spatiotemporal distribution of tropospheric ozone concentration of 0.2-3km can be detected.The comparison with the ozone lidar based on the gas Raman technology shows that the lidar has a significant improvement in spatial and temporal resolution and signal-to-noise ratio.On this basis,the integrated verification of the movable ozone lidar was carried out,and the mobile observation experiments were carried out in the areas with high incidence of ozone pollution in summer to quickly obtain the regional ozone concentration distribution profile,which illustrates the ozone differential absorption lidar based on the solid Raman technology Feasibility and reliability of mobile observations.In addition,the paper also shows the airborne observation experiment of the ozone differential absorption lidar,and it also shows the effectiveness and reliability of the observation on the fast platform.It shows that the solid Raman laser light source has a series of advantages such as good reliability,high seismic performance and high system stability.