Very short wavelength (λ=3.1–3.3μm) quantum cascade lasers

Quantum cascade lasers emitting at wavelengths as short as 3.1–3.3μm are reported. Such high intersubband emission energies (up to 400meV) have been obtained thanks to the high conduction band offset of the InAs∕AlSb material system. The structures, grown by molecular beam epitaxy on InAs substrates, are based on the bound-to-continuum design and use a low loss plasmon enhanced waveguide consisting of n+-InAs cladding layers with InAs∕AlSb superlattice spacers surrounding the active zone. The lasers exhibit threshold current densities close to 3kA∕cm2 at 83K and operate in pulsed mode up to 240K.