The propagation loss of ultrashort laser pulses in water clouds

Abstract

When a high-power laser beam is incident on water clouds, often along with optical breakdown occurs. In that case, the droplet becomes highly opaque and strongly absorbs incident laser light. In this study, we construct a transient coupling model to elucidate the evolution of the light field and the distribution of plasma in the interaction between laser and cloud droplet in detail, and further quantify the nonlinear absorption of droplet under the action of high-power laser. The results showed that linear dependence existed between the proportion of absorbed energy by the droplet and the incident laser wavelength at the same laser energy. Such a relationship, combined with existing scattering theory, can be used to evaluate the propagation distance of the ultrashort laser in water clouds and the specific light attenuation under different parameters. In the same type of water cloud, the laser propagation distance decreases with increasing laser intensity, thereby confirming the availability of non-linear absorption on the laser propagation. Furthermore, a smaller pulse duration typically corresponds to a larger peak power, which results in stronger non-linear absorption and a shorter propagation distance in water clouds. On the other hand, a comparison of laser propagation distances in different types of water clouds reveals that scattering effects dominate in dense water clouds, with stronger propagation losses to the incident laser. Finally, the light attenuation in different water clouds is given accordingly. This study opens up new perspectives for the assessment of laser propagation loss in different water clouds and the propagation distance.