| Popis: |
Laser cooling of gallium arsenide is of high industrial and academic interest and has been actively investigated using different experimental methods based on steady-state concepts. We demonstrate for the first time an onset of transient cooling in GaAs after an impulsive excitation, verified by two independent methods of time-resolved spectroscopy. We observe that transient cooling lasts for about 100 ps, becoming overwhelmed on longer timescales by parasitic heating associated with the nonlocal character of the background absorption processes. In addition, new insights into the physics of the Urbach tail excitation, being at the heart of the laser cooling in semiconductors, are revealed. |
