Room-temperature long-wavelength (λ = 13.3µm) unipolar quantum dotintersubband laser

Abstract
Long-wavelength (λ = 13.3 µm) unipolar lasing at 283 K from self-organised In0.4Ga0.6As/GaAs quantum dots, due to intersubband transitions in the conduction band, is demonstrated for the first time. The threshold current density under continuous wave operation is 1.1 kA/cm2 for a 60 µm × 1.2 mm broad-area plasmon-enhanced waveguide device and the maximum power output is ≃ 1 µW. The long intersubband relaxation time in quantum dots, together with the short lifetime in the ground state, due to interband stimulated emission, help to achieve the necessary population inversion and gain.