转动能级拉曼抽运技术在NO_2激光探测雷达中的应用

Novel Approach of Stimulated Rotational Raman Scattering Used in NO_2-DIAL System

差分吸收激光雷达(DIAL)是目前探测大气污染成分最有效的方法之一。介绍了一种新型NO_2激光探测雷达(N(O_2-DIAL)差分吸收光源的设计:选择Nd:YAG的三倍频输出激光作为λ_(on)(354.7nm),并采用该三倍频激光的圆(或椭圆)偏振光抽运D_2拉曼池,选择其中距抽运光波长最接近的第一级纯受激转动拉曼散射光作为特征吸收波长λ_(off)(359.9nm)。抽运光的偏振态调制采用1/4波片调谐技术方便地测定和实现。这一方法保证了两个差分激光的中心波长稳定、频漂小、线宽窄,同时系统只需使用一个拉曼池,即可获得同轴性很好的两束激光输出,在技术指标的提升和经济性两方面都具有很大的优势。

Differential Absorption Lidar （DIAL） for detecting atmospheric pollution is used extensively for its high precision and spatial resolution. A new approach is presented for obtaining the differential absorption light sources in design of the new type NO2-DIAL. We take the third harmonic of Nd：YAG laser itself as the selected λon（354.7nm）, and also converted it to the circularly or elliptically polarized laser to pump the D2 Raman cell. The first-order pure stimulated rotational Raman scattering light nearest to the pumping laser wavelength is taken as the λoff（359.9nm） for DIAL. The polarization state of the pumping laser can be conveniently modulated by using a λ/4 wave-plate. This design ensure the stability of the centre wavelength of the couple absorption lights and will achieve smaller frequency shifting and narrower linewidth. In addition, the system can get the two output specific beams with excellent coaxiality requiring only one Raman cell. It is of large advantages in raising the technical performance and the economical efficiency.