Shortening of ultrashort optical pulses colliding in a dye solution

A numerical analysis is made of the changes in the parameters of ultrashort optical pulses interacting in a bleachable dye solution. It is is found that the pulse durations may increase or decrease depending on the position of the dye layer relative to the meeting point of the pulses. The shortening of the pulses may be up to an order of magnitude greater than the known reduction of the duration due to absorption of the leading edge when a pulse passes once through a solution.