Figure 2

(a–d) Time-domain P-polarized THz waveforms radiated from the (111) surface of n-type Cu_0.02Bi₂Se₃ and p-type Bi₂Te₃ by P- and S-polarized optical pulse excitation. In (a), the thin-red line represents the 0.015-times smaller P-polarized THz wave that is generated from an n-type InAs under the same conditions. In both P_Opt-P_THz and S_Opt-P_THz configurations, the polarities of the P-polarized THz waveforms from p-type Bi₂Te₃ (c,d) are in the reverse of that from n-type Cu_0.02Bi₂Se₃ (a,b). A_THz is the peak-to-peak value of the THz waveform. (e–h): the plots of A_THz for the P-polarized THz waveforms as a function of azimuthal angles (-scan) of Cu_0.02Bi₂Se₃ (a,b) and Bi₂Te₃ (c,d) single crystals (black). The corresponding XRD -scans for the (1 1 15) peak for both single crystals are also shown in (e–h) (green).