Abstract

Coherent phonons excited in various solid- state materials, such as semiconductors and semimetals, have been so far studied extensively by measuring the transient reflectivity or transmittance. However, results only for the Raman-active phonon modes have been reported, whereas the only-infrared(IR)-active (Raman-inactive) phonon modes have not been observed except in extraordinary crystal conditions. Recently, emission of coherent terahertz (THz) radiation from the coherent phonons of the only-IR-active-modes excited in Te was reported.¹ Such observation of the radiation from coherent phonons enables us the direct observation of coherent phonon dynamics for the IR-active modes which are not accessible by the standard transient reflectivity/transmittance measurements.

© 1998 Optical Society of America