1.26 $\mu$m intersubband transitions in In$_{0.3}$Ga$_{0.7}$As/AlAs   quantum wells
  We observed room-temperature intersubband transitions at 1.26 microns in n-doped type-II In$_{0.3}$Ga$_{0.7}$As/AlAs strained quantum wells. An improved tight-binding model was used to optimize the structure parameters in order to obtain the shortest wavelength intersubband transition ever achieved in a semiconductor system. The corresponding transitions occur between the first confined electronic levels of the well following mid-infrared optical pumping of electrons from the barrier X-valley into the well ground state. 
Cesar Pascual Garcia, Andrea De Nardis, Vittorio Pellegrini, Jean Marc   Jancu, Fabio Beltram, Bernhard H. Mueller, Lucia So...