FIR quantum cascade lasers at lambda > 20 pm and THz emitters at lambda=80 mu m

Quantum cascade lasers operating at lambda > 20 mum wavelength are reported. Pulsed operation as obtained up to 140 K with a peak power of few milliwatts at cryogenic temperatures, Laser action originates from interminiband transitions in ``chirped'' superlattice active regions. The waveguides are based on surface-plasmon modes confined at a metal semiconductor interface, but we also report on a 21.5 mum wavelength laser based on a double-sided interface-plasmon waveguide. This latter, contrary to the single-sided surface plasmon, is a viable waveguiding solution in the THz range, i.e. at wavelengths between 60 and 100 mum. Finally, intersubband electroluminescence is reported in a quantum cascade structure based on asymmetric superlattice active regions and designed for emission in the THz range at lambda approximate to 80 mum. (C) 2002 Published by Elsevier Science B.V.