Ultrafast lattice-bonding dynamics of tellurium

Summary form only given. We present a study of the ultrafast bonding dynamics of tellurium in the presence of a symmetry-preserving coherent phonon. The coherent phonon modulates the band structure at THz frequencies. We measure the dielectric function, because it is closely related to the band structure, over a broad frequency range (1.8 eV to 3.4 eV) following excitation by an 800-nm, 50-fs pump pulse. In order to measure the two independent components of the dielectric tensor of a uniaxial material (/spl epsiv//sub ord/(/spl omega/) and /spl epsiv//sub ext/(/spl omega/)), four pump-probe measurements are required. Each component describes the optical properties along certain directions in the crystal: /spl epsiv//sub ord/(/spl omega/) corresponds to the ab-plane and /spl epsiv//sub ext/(/spl omega/) to the c-axis (helical axis). The symmetry-preserving phonon mode excited in Te is confined to the ab-plane, so we expect that the ordinary dielectric function will be most sensitive to these oscillations.