Studying periodic nanostructures by probing the in-sample optical far-field using coherent phonons

Abstract

Optical femtosecond laser pulses diffracted into a crystalline substrate by a goldgrating on top interact with gigahertz coherent phonons propagating towards the grating from the opposite side. As a result, Brillouin oscillations are detected for diffracted light. The experiment and theoretical analysis show that the amplitude of the oscillations for the first order diffracted light exceeds that of the zero order signal by more than ten times. The results provide a method for internal probing of the optical far-field inside materials containing periodic nanostructures.