Fig. 1. (a) Experimental setup of optical pump-probe spectroscopy in reflection configuration; (b) typical optical pump-probe signal of GaAs.(a)反射式光学抽运-光学探测光路; (b)GaAs的典型的光学抽运-光学探测信号

Fig. 2. (a) Electro-optic sampling^[15]; (b) experimental setup of OPTP spectroscopy. (a) 电光采样法^[15]; (b) OPTP光谱光路示意图

Fig. 3. (a) Schematic of magneto-optic Kerr effect^[9]; (b) TRKR^[8] via pump-probe technique. (a)磁光克尔效应的原理^[9]; (b)基于抽运-探测技术的时间分辨克尔旋转光谱示意图^[8]

Fig. 4. Schematic of (a) ARPES and (b) Tr-ARPES^[23] setups. (a) ARPES 和(b) Tr-ARPES^[23]实验平台示意图

Fig. 5. (a), (b) Transient reflectivity of Bi₂Se₃ measured via OPOP at room temperature^[7,11]. The red squares in (b) show the full width half maximum of the probe light’s spot as a function of delay time^[11]. (a), (b)室温下Bi₂Se₃单晶的OPOP信号^[7,11], 其中图(b)中红色方框为探测光在Bi₂Se₃样品表面上的光斑的半高全宽随时间延时的变化^[11]

Fig. 6. OPTP signals of Bi₂Se₃ thin film^[32]: (a) Conductance of Bi₂Se₃ without optical pump; (b) transmitted terahertz electric field after sample under optical pump; (c), (d) transient THz peak signal of samples with different thickness and pump power; (e)—(h) scattering rate and plasma frequency obtained from the fitting of conductance of Bi₂Se₃ by Drude-Lorentz model with different sample thickness and pump delay. Bi₂Se₃薄膜的OPTP信号^[32] 　(a)无光抽运下的Bi₂Se₃电导; (b)有光抽运下透过Bi₂Se₃的太赫兹波形; (c), (d)不同样品厚度以及不同功率下太赫兹电场峰值随着抽运延时变化; (e)—(h)为在不同抽运延迟下, 通过用Drude-Lorentz拟合的对于不同厚度样品散射率和等离子频率

Fig. 7. (a), (b) OPTP signals of Bi_1.5Sb_0.5Te_1.7Se_1.3 (BSTS) and Bi₂Se₃; (c), (d) schematic diagrams of energy bands and electron transfer in BSTS and Bi₂Se₃^[35](a), (b) Bi_1.5Sb_0.5Te_1.7Se_1.3(BSTS)和Bi₂Se₃的OPTP信号; (c), (d)BSTS和Bi₂Se₃的能带结构示意图和电子转移^[35]

Fig. 8. Experimental Tr-ARPES data^[13]: (a) The relaxation process for different bands of p-doped Bi₂Se₃ excited by light; (b) schematic of the electronic band structures of Bi₂Se₃ for reference; (c) electronic band structures for Bi₂Se₃, and the surface states and bulk conduction band are unoccupied due to the Fermi energy sitting inside the bulk valence band; (d) electrons are excited to high energy band after the excitation; (e)–(g) relaxation process of high energy electrons. Bi₂Se₃的Tr-ARPES信号^[13] 　(a) p型掺杂的Bi₂Se₃受光激发后不同能带的弛豫过程; (b)用于参考的Bi₂Se₃的能带; (c)平衡态Bi₂Se₃的能带结构, 由于掺杂导致费米能级较低, 表面态和体态导带并没有被占据; (d)在刚刚被抽运光激发时, 电子被激发到较高能级处; (e)—(g)则描述了较高能量的电子的弛豫过程

Fig. 9. Electron temperature of Bi₂Se₃ obtained by Tr-ARPES from Shen's group (a)^[13] and Gedik's group (b)^[36]. 由Shen研究组(a)^[13]和Gedik研究组(b)^[36]利用Tr-ARPES所测得的Bi₂Se₃电子温度数据

Fig. 10. OPOP experimental data and Fourier transform of the oscillatory data for Bi₂Se₃ at 293 K^[8]. Bi₂Se₃的OPOP实验数据及其傅里叶变换结果^[8]

Fig. 11. Experimental Tr-ARPES data of Bi₂Se₃^[48]. Bi₂Se₃的Tr-ARPES实验数据图^[48]

Fig. 12. Photoinduced relaxation processes of carriers and spin in Bi₂Se₃^[14]: (a)−(d) correspond to the relaxation processes of different time scales Bi₂Se₃中载流子和自旋在光激发下的弛豫过程图示^[14] 　(a)−(d)不同时间尺度下的弛豫过程

Fig. 13. (a) Time-resolved Kerr rotation of Bi₂Se₃ at 10 K and 80 K. Red line indicates that the pump laser is left circularly polarized while the blue one is right circularly polarized^[8]. (b) Time-resolved Kerr rotation of Bi₂Se₃ excited at different photon energies for different temperatures^[8]. (c) fittings of the TRKR experimental data for Bi₂Se₃^[8]. (d) Kerr rotation experimental data via second harmonic generation(oblique pump)^[14]. (e)−(h) transient reflectivity corresponding to the left and right circularly polarized pump light^[53]. (a) Bi₂Se₃样品在10 K和80 K时的克尔转角光谱, 红线代表抽运激光为左旋圆偏振光, 蓝色实线代表右旋圆偏振光^[8]; (b) Bi₂Se₃样品在不同光子能量和不同温度下的克尔转角光谱^[8]; (c) Bi₂Se₃实验数据拟合^[8]; (d)二次谐波克尔光谱(斜入射抽运光)测得的实验数据^[14]; (e)−(h)左右圆偏振光激发后反射率变化随时间变化的实验数据^[53]

Fig. 14. Schematic of photo-excitation processes via light with different photon energies in Bi₂Se₃^[8]. Bi₂Se₃在不同光子能量激发下的能带跃迁示意图^[8]