Nanosecond laser pulse propagating through turbid media: a numerical analysis

Abstract

A short pulse transmitted by a turbid medium is both distorted in shape and shifted temporally as its passes through. If the incident pulse is short enough an analytical expression of the deformed pulse can be calculated using the diffusion approximation of the radiative transport equation (RTE), and the optical properties of the medium can be recovered from the transmitted pulse. In this work, the effect of a homogeneous turbid medium on the transmitted temporal profile of nanosecond laser pulses was studied both experimentally and numerically for samples with different optical properties and various laser pulse widths. The numerical results showed a dependence of the pulse distortion on the variables tested, finding that this dependence dramatically changes upon varying pulse width. This work contributes to the field by showing that the interaction between turbid media phantoms and nanosecond laser pulses can also be analyzed, as it is the case for ultrashort laser pulses, by using the diffusion approximation of the RTE in certain regimes. This finding is significant and useful for applications when a laser pulse must attain to certain duration and shape after propagation through a turbid medium or when at a certain time an intensity threshold is required.