Wideband pulse propagation: Single-field and multifield approaches to Raman interactions

We model the process of ultrabroadband light generation in which a pair of laser pulses separated by the Raman frequency drive a Raman transition. In contrast to the usual approach using separate field envelopes for the different frequency components, we treat the field as a single entity. This requires the inclusion of few-cycle corrections to the pulse propagation. Our single-field model makes fewer approximations and is mathematically (and hence computationally) simpler, although it does require greater computational resources to implement. The single-field theory reduces to the traditional multifield one using appropriate approximations.

Figure 1

Transient Raman generation using 17.5-fs and 62.5-f pump pulses as described in the text. Here we compare three simulation results: (a) single-field GFEA simulation, (b) multifield simulation, and (c) single-field SVEA simulation. The dashed lines help compare the relative heights of the first Stokes and anti-Stokes peaks. The vertical scale is in arbitrary units.

Figure 2

10-fs probe pulse incident on a medium with an initial polarization of ${\rho }_{12}=0.025ı$. Here we compare three simulation results: (a) single-field GFEA simulation, (b) multifield simulation, and (c) single-field SVEA simulation. The dashed lines help compare the relative heights of the first Stokes and anti-Stokes peaks. The vertical scale is in arbitrary units.