Sandra G. Malhotra

Picosecond ultrasonics study of the vibrational modes of a nanostructure

We report experiments in which a subpicosecond pump light pulse is used to excite vibrations in a nanostructure consisting of a periodic array of copper wires embedded in a glass matrix on a silicon substrate. The motion of the wires after excitation is detected using a time-delayed probe light pulse. From the measured data, it is possible to determine the frequencies νn and damping rates Γn of a number of the normal modes of the structure. These modes have frequencies lying in the range 1–30 GHz. By comparison of the measured νn and Γn with the frequencies and damping rates calculated from a computer simulation of the vibrations of the nanostructure, we have been able to deduce the vibration patterns of six of the normal modes.

A study of the vibrational modes of a nanostructure with picosecond ultrasonics

Abstract We describe experiments in which a sub-picosecond pump light pulse is used to excite vibrations in a nanostructure. The sample consists of a periodic array of copper wires embedded in a glass matrix on a silicon substrate. The motion of the wires after excitation is detected using a time-delayed probe light pulse. From the data, it is possible to determine the frequencies ν n and damping rates Γ n of a number of the normal modes of the structure. These modes have frequencies lying in the range 1–30xa0GHz. By comparison of the measured ν n and Γ n with the frequencies and damping rates calculated from a computer simulation of the vibrations of the nanostructure, we have been able to identify the different normal modes and deduce their vibration patterns.