Transient reflectivity pump-probe experiments are performed on a single gold particle to analyze the vibration
of the particle as well as the propagation of the resulting GHz acoustic wave in the embedding medium. In a
first part, the vibration of a single 430 nm diameter gold particle embedded in a silica matrix is investigated.
A semi-analytical model is presented and demonstrates that the detection mechanism relies on an intrinsic
common-path interferometer which directly images the particle interface displacement. The coherent phonon
propagation inside the embedding medium is then studied in the case of a gold particle embedded in an
agarose gel. A comparison between experimental results and calculations suggests a detection of the Brillouin
scattering in agarose, so long as the Brillouin frequency at the considered probe wavelength matches the
fundamental breathing mode frequency (or one of its harmonics) of the particle.
We have fabricated three-dimensional (3D) colloidal crystals containing a defect by the Langmuir-Blodgett (LB) technique. A controlled number (from one to four) of layers of colloidal silica particles were inserted between two opal films of silica spheres of different size. The presence of the extrinsic defect led to an impurity mode within the photonic stop band, which was observed as a pass band in the near-infrared (NIR) spectra. The position of this defect mode was found to vary periodically with the value of the ratio of the thickness of the defect to the diameter of the colloids of the upper and lower opals. We also show that the amplitude of the pass band in the band gap is maximum when the two opals confining a defect monolayer made of smaller colloids have the same number of layers.