Acoustic spectroscopy for studies of vitreous silica up to 740 GHz

Due to the high attenuation in vitreous silica, acoustic attenuations in the THz regime are typically measured by incoherent techniques such as Raman, neutron, and X-ray scattering. Here, we utilized multiple-quantum-well structures to demonstrate acoustic spectroscopy of vitreous silica up to ∼740 THz. The acoustic properties of silica thin films prepared by physical and chemical deposition methods were characterized in the sub-THz regime. This technique can be useful in resolving debated issues relating to Boson peak around 1 THz.