THz Emission by Coherent Lattice Vibrations in Tellurium

We report on the time-resolved observation of coherent infrared-active phonons excited by fs-laser pulses in single crystal Tellurium. The coherent lattice vibrations are detected in an optical pump-probe experiment in amplitude and phase. The emission of electromagnetic waves at THz frequencies associated with the coherent lattice vibration is observed. This is the first demonstration of THz emission by coherent phonons for any semiconductor.