Control of the duration of picosecond infrared pulses in semiconductors with variable dispersion

A method is proposed for altering the duration of picosecond radiation pulses by direct control of the group velocity. In semiconductor media such control can be implemented by altering the density of free carriers N_e during the passage of a pulse. Different mechanisms of changes in N_e are considered and these result in shortening or lengthening of infrared radiation pulses.