Few-cycle pulse propagation in multiple scattering media

The propagation of an ultrashort pulse (pulsewidth ∼8 fs), comprised of few optical cycles, through a strongly scattering random medium is studied using Monte-Carlo simulations. The disordered medium is made up of passive high-index sub-wavelength sized alumina microspheres. The transmitted pulse decays non-exponentially, exhibiting a significant departure from typical diffusive profiles. This effect originates from the frequency response of the multiple scattering medium. A strong spectral shift in the transmitted pulse profile with time is observed, suggesting a positive chirp-like phenomenon in random media. The chirp depends upon scatterer size and degree of disorder, and not on the dispersive properties of the scatterer. The relevance of these investigations on biological imaging through turbid media is discussed, including the possibility of a novel gating technique to extract images from turbid media using few-cycle pulses.