Fig. 2.

Illustration of the THz pulse incident on the front surface of the silicone at 30° and refracted due to the refractive index n_THz before being reflected from the embedded TiO₂ layer at location 1 and silicone back interface at location 2. The angle ϑ₂ is unknown in this case since it depends on n_THz, and n_THz is assumed to be unknown. The time-of-flight for a normally incident THz pulse is shown as t_THz, while the measured time-of-flight of the THz pulse, incident at 30° is t_THz30.