Time-domain spectroscopy of coherent optical phonons in bismuth germinate (Bi4Ge3O12) is presented. Utilizing both impulsive stimulated Raman scattering and time-domain terahertz spectroscopy, more than 12 unique vibrational states ranging in frequency from 2 to 11 THz are identified, each with coherent lifetimes ranging from 1 to 20 ps. These modes are highly sensitive to crystal orientation and demonstrate frequency shifts on picosecond timescales consistent with an anharmonic lattice potential.

We report the generation of high wavevector, large amplitude coherent optical phonons in a microstructured Bismuth film. A femtosecond laser pulse optically excites a periodic micron scale grating etched into a Bismuth film. The ultrafast excitation produced coherent optical phonon oscillations with wavevectors as large as 1 microm(-1), providing a possible method of generating an efficient sub-picosecond switch for hard x-rays.