Picosecond photon echoes detected by optical mixing

Picosecond photon echoes are shown to be easily detected by optical mixing. The synchronized picosecond excitation and probe pulses are generated by amplifying pulses from two dye lasers, synchronously pumped by a mode-locked argonion laser. The technique is used to study optical dephasing in the organic mixed crystal of pentacene in p-terphenyl.