  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.
