Ultrafast expansion of electron-hole plasma in GaAs probed by THz radiation

• Main Authors: Ostatnicky, Tomas, Klimovic, Filip, Troha, Tinkara, Kadlec, Filip, Kuzel, Petr, Nemec, Hynek
• Format: Conference Proceeding
• Language: English
• Subjects: Crystals; Gallium arsenide; Optical solitons; Stimulated emission; Surface waves; System dynamics; Temperature distribution
• ISSN: 2162-2035
• DOI: 10.1109/IRMMW-THz57677.2023.10299363

Ultrafast and long-distance expansion of electron-hole plasma in bulk GaAs crystal at temperatures ranging from 20 K to 300 K is observed by means of the optical pump - THz probe experimental technique. The expansion speed \sim c/50 at 300 K notably exceeds values reported earlier in the literature but it also exceeds the values permitted by the GaAs band structure for a bare electron. This observation is interpreted in terms of a stimulated emission, fast transport and reabsorption of photons by creation of electron-hole pairs. Theoretical quantitative model, based on the above interpretation, shows a very good agreement with the experimental data, gives a valuable insight into the system dynamics and predicts conditions at which the effect should be observable. At temperatures below 100 K, further increase of the propagation speed of electron-hole plasma surface (up to \sim c/10) is observed. This effect is interpreted as the direct observation of the optical soliton propagation in the crystal.