High Energy Intersubband Transitions in InAs/AlSb QWs

InAs/GaSb/AlSb heterostructures are a promising material system for intersubband optically-pumped applications due to their large conduction band offsets ($\sim $2 eV in InAs/AlSb). Applications include FIR generation and ultrafast all-optical switching at the communication wavelength of 1.55 $\mu $m. We have observed intersubband absorption at E$_{12}$ up to 670 meV (1.85 $\mu $m) in 2.1 nm Si-doped InAs/AlSb QWs. We have also attempted THz generation by difference frequency mixing in resonant InAs/AlSb asymmetric double quantum wells.