2-m Ho emitter-based coherent DIAL for CO₂ profiling in the atmosphere

We report on the use of a thulium-fiber-pumped holmiumbased emitter in a coherent differential absorption lidar (CDIAL) experiment for high time and space resolution of CO₂ absorption field in the atmosphere. The 2-m high-power dual-wavelength single-mode Q-switched Ho:YLF oscillator delivers 10-mJ pulses with a duration of 40 ns at 2 kHz. Both short pulse duration and high repetition rate were chosen to increase the DIAL precision and time and space resolution in coherent detection. The CDIAL provides 150-m range and 15-min time-resolved CO₂ absorption coefficient with a calculated instrumental error of 0.5% at 500 m and less than 2% at 1 km. Dry-air CO₂ mixing ratio estimates from the DIAL system are compared with simultaneous in situ gas analyzer measurements during a 20-h-long experiment.