Midinfrared femtosecond laser pulse filamentation in hollow waveguides: A comparison of simulation methods

摘要

This work compares computational methods for laser pulse propagation in hollow waveguides filled with rarengases at high pressures, with applications in extreme nonlinear optics in the midinfrared wavelength region. Asnthe wavelength of light λ = 2π/k increases with respect to the transverse size R of a leaky waveguide, the lossnof light out of the waveguide upon propagation, in general, increases. The now standard numerical approachnfor studying such structures is based on expansion of the propagating field into approximate leaky waveguidenmodes. We compare this approach to an improved method that resolves the electric field in real space andncorrectly captures the energy loss through the waveguide wall. The comparison reveals that the expansion-basednapproach overestimates losses that occur in nonlinearly reshaped pulsed waveforms. For a modest increase inncomputational effort, the alternate method offers a physically more accurate model to describe phenomena (e.g.,nextreme pulse-selfcompression) in waveguides with smaller values of kR.