Design results are presented for the quantum parallel laser (QPL) at 1–20 μm wavelengths and the cryogenic 4–20 μm quantum cascade laser (QCL). For 1–2 μm lasing, the optimum multiple quantum well heterostructures are Si quantum wells (QWs) confined by wide-gap lattice-matched semiconductor layers, especially the Si/ZnS, Si/BeSeTe, Si/γ–Al2O3, Si/CeO2, and Si/SiOx systems (SiOx is a crystalline suboxide). The electrically pumped 300 K unipolar p-i-p. QPL consists of tightly coupled QWs exhibiting coherent transport of carriers on superlattice (SL) minibands. A good QPL candidate is the symmetrically strained Gen–Sin SL grown on relaxed Si0.5Ge0.5. Local-in-k population inversion is engineered between two valence minibands. Our calculations indicate that the p-i-p QCL is feasible in Ge–Si or in lattice-matched Si0.63Ge0.33C0.04/Si. The oscillator strength fz=0.1 calculated for the 8 ML×8 ML Si/ZnS zone-folded SL is insufficient for 1.1 μm band-to-band lasing; however, the in-plane dispersion of Si QWs in Si/ZnS SLs shows valence subbands that are sufficiently nonparabolic for local-in-k lasing in QPLs and QCLs. © 1998 American Vacuum Soc- - iety.