Infrared Piezoabsorption of Silicon in the Multiphonon Spectral Range

Piezoabsorption measurements have been performed on silicon in the multiphonon spectral range (500 to 1000 cm−1). Uniaxial stress along [100] is applied and the light is polarized parallel and normal to the stress axis (‖ and ⟂ [100]). The change of the absorption constant induced by hydrostatic pressure is calculated from the results. Sign and location of the piezoabsorption bands yield a topological classification for the critical points which give rise to the two‐phonon absorption structure in silicon.