Figure 2.

(a) Brillouin light scattering (BLS) spectra for in-plane phonon propagation at q = 0.013 55 nm^–1. The polarized spectra (in the range of −8 to 8 GHz) are represented by single Lorentzian peaks for the bulk TE (black line) and TE/TiO₂ nanocomposite (red line for TiO₂-30 wt % and blue line for TiO₂ nanoparticle films). The depolarized BLS spectrum of the bulk TE (in the range of −4 to 4 GHz) is also represented by a single Lorentzian peak (gray line), indicating a weak cross-linked structure of TE matrix. (b) The phonon dispersion relations for these three compositions shown with the same color are linear, f(q) ∼ q, as indicated by the four black lines.