Design and analysis of Si/CaF 2 near-infrared ( λ ∼ 1.05 μm) DFB quantum cascade laser with wide transition layer

Abstract In this paper, we have designed and analyzed a room temperature near-infrared quantum cascade laser with wavelength of λ = 1.05 μm from Si/CaF 2 heterojunction and distributed feedback conduction layer (CL). The designed device contains multi-Si/CaF 2 active layer on n-Si (111) layer of a silicon-on-insulator substrate, forming a single-mode propagation waveguide in transverse magnetic mode. We innovatively designed the active layer structure that consists of a 12-monolayer (ML) transition layer quantum well (QW), quad-injector-barrier and a 4-ML blocking layer, with transition from 4th state to 1st state in QW. The minimum threshold current density of 7.32 kA cm −2 was obtained at waveguide width of 0.25 μm, period number of 15, and CL thickness of 25 nm, which is lower than calculated injection current density of 31 kA cm −2 ; in addition, the inter-subband relaxation time from 4th state to 1st state τ 41 and the lifetime of 1st state τ 1 , are roughly estimated to be 1.5 ps and 0.7 ps, which ensures population inversion. The analysis above indicated the possibility of laser oscillation.