Using a photo-acoustic cell to manage pulsed laser spectral shift:application to accurate atmospheric CO_2 Heterodyne Differential Absorption Lidar measurements

摘要

A photo-acoustic technique is implemented into a 2-μm heterodyne differential absorption lidar. A 1-bar CO_2-filled PAC enabled us to select on- and off-line signals and to prevent from mode hopping. Moreover, it can be used to correct from the emitter spectral drift provided that the signal to noise ratio is sufficient and that the spectral characteristics of the absorption are known with accuracy. From then on a 1% of accuracy has been demonstrated for the PAC used in this experiment. For CO2 HDIAL measurement, the PAC error has to be added to the statistical error from the slope method calculations developed in Ref. 5.