Optical response of semiconductor nanostructures in terahertz fields generated by electrostatic free-electron lasers

Semiconductor heterostructures are the foundations for revolutionary advances in solid-state optical devices of the last few decades. The family of semiconductors that has had the largest impact is based on elements from groups III (Ga, In, Al) and V (In, As, Sb, N) in the periodic table. Of these so-called III-V semiconductors, the gallium arsenide (GaAs) aluminum gallium arsenide (AlxGa1-xAs) system is the favorite of optical physicists. GaAs can be grown very cleanly by molecular beam epitaxy, and has a direct bandgap near 300 THz (1.5 eV) at low temperatures. This photon energy is extremely convenient for state-of-the-art detectors and sources of near-infrared (NIR) radiation.