The intensity of the early-arriving snake portion of 100-fs ultrashort laser pulses transmitted through biological tissue of increasing thickness was measured by a streak camera. The snake photon intensity within the first arrival time interval. Δt was found to decrease exponentially with tissue thickness (z) as I(Δt) = I0A exp[−b(Δt)z/lt], where I0 is the incident laser pulse intensity, lt is the transport mean free path of the medium, and the parameters b and A depend on the time interval Δt. This result shows that the intensity of snake photons decays significantly more slowly than that of ballistic photons as tissue thickness increases.
© 1994 Optical Society of AmericaFull Article | PDF Article