Supercontinuum from an ultra-thin slab of two-level atoms ensemble

Highlights: • Supercontinuum spectral width increases initially with pump intensity before it saturates. • Spectrum from a slab of thickness = $\left(m+\frac{1}{4}\right)\lambda is$characteristic of one-mode dominance. • Spectrum from a slab of thickness = $m\lambda /2$ reflects competition between two leading modes. I investigate the effects of intermodal interference on the supercontinuum generated from a very thin sample of two-level system. I find that: (i) in all cases, the spectral width of the emitted radiation increases with the pump intensity to reach a saturated value; (ii) for slabs with one dominant mode [thickness equal to $(m\pm \frac{1}{4})\lambda$, where m is an integer and $\lambda$ is the wavelength of the atomic resonance frequency] the value of the saturation spectral width increases almost linearly with the slab thickness; and (iii) for slab thicknesses not on this lattice, the value of the spectral width is not a monotonic function of the slab thickness.