Figure 3: Azimuth dependence and dominant components of THz signal Sx.
From: Ultrafast photocurrents at the surface of the three-dimensional topological insulator Bi2Se3
(a) THz signal waveforms at various sample azimuth angles ϕ and for fixed pump polarization. (b) Extracted THz amplitude versus ϕ for various pump-polarization settings (→ and differential signals ↖−↗ and 
−
). While both Sx and Syz exhibit a 3ϕ-type-dependent component of comparable magnitude, Syz has a much larger and dominant component independent of ϕ. (c) Dominant temporal components of signal sets Syz(t, ϕ) and Sx(t, ϕ) for various pump polarizations, extracted by using equation (2) (see the ‘Methods’ section).
