Fig. 1. Schematic diagram of OPTP lightpath

Fig. 2. UV-Vis absorption spectrum of GaSb at room temperature

Fig. 3. Relationship between change rate of terahertz peak intensity and both the energy density and delay time of pump light. (a) Variation in change rate of terahertz peak intensity with delay time under different energy densities of pump light; (b) variation in maximum change rate of terahertz peak intensity with energy density of pump light

Fig. 4. Variation in carrier recombination time with energy density of pump light

Fig. 5. Terahertz time-domain and frequency-domain intensity spectra of GaSb under different energy densities of pump light (illustrated as locally enlarged images). (a) Terahertz time-domain spectra; (b) terahertz frequency-domain intensity spectra

Fig. 6. Real part and imaginary part of the conductivity of GaSb under different energy densities of pump light. (a) 45 μJ/cm²; (b) 93 μJ/cm²; (c) 240 μJ/cm²