Effective nonlinear rovibrational response of water vapor for efficient pulse propagation simulations

The long-range delivery of high-energy, long-wavelength pulses over kilometer ranges in the atmosphere could be potentially offset by nonlinear spectrally broadband responses of hundreds of thousands of nearby rovibrational transitions of water, CO ₂ , and other atmospheric constituents. To study this scenario, an effective multi-level optical Bloch-equation-based approach is developed, extending the linear response of the HITRAN database to capture the nonlinear rovibrational response of water vapor. The model is sufficiently compact and computationally efficient to source the unidirectional pulse-propagation equation and enable the first study of long-range, 10 μm pulse delivery over hundreds of meters to kilometer distances. The simulation results clearly show that long-range delivery is possible due to the low peak intensities achieved in self-trapped multi-Joule pulses.