Fourier spatial filter acts as a temporal gate for light propagating through a turbid medium.

The temporal profiles of ultrashort light pulses propagating through turbid media of different lengths were measured with a streak camera. Various Fourier spatial filters were used to select the spatial frequencies of the scattered pulses. The temporal profiles of the pulses scattered by a 0.4% Intralipid solution in a cell of 5-cm thickness were signif icantly narrowed because of the removal of the higher-frequency components by a Fourier spatial filter.