Controlling the photoluminescence of gallium arsenide with trains of ultrashort laser pulses

A train of three equally spaced femtosecond laser pulses is used to induce electron recombination in GaAs 100 . Photoluminescence from the E1 transition is observed when the spacing between the pulses is an integer multiple of the longitudinal-optical phonon period. This effect is also controlled by varying the relative optical phase and the polarization plane of the pulses. These observations are explained by a mechanism in which hot electrons excited in a plasma collide with the underlying lattice to produce coherently excited phonons, which scatter carriers into the L valley, where they recombine.