Time-Resolved Observations of Soft Phonon Modes in Strained BaTiO$_{3}$/Si Heterostructures*

Ferroelectric thin films such as BaTiO$_{3}$, grown on Si(100) substrates, have enormous potential for applications ranging from non-volatile random access memories to electro-optic gates for quantum information processing architectures. Optical techniques provide powerful means for obtaining time-resolved information about the ferroelectric soft mode in these materials. Using a two-color pump-probe arrangement, we observe THz-frequency soft modes in strained BaTiO$_{3}$/Si heterostructures grown by oxide-molecular beam epitaxy.