Low-internal-loss separate confinement heterostructure InGaAs/InGaAsP quantum well laser.

An InP-based separate-confinement-heterostructure quantum-well (SCH QW) laser grown by atmospheric pressure metal-organic vapor deposition (MOCVD) is discussed. This growth technique provides very precise thickness control and good layer uniformity for multiple-quantum-well (MQW) material, allowing quantum wells as thin as 10 angstrom to be reproducibly grown. For the present laser four narrow (80-angstrom each) InGaAs quantum wells surrounded by 1.3-μm bandgap InGaAsP barriers, which also provide the separate optical confinement, were grown. The operating wavelength shifts from 1.67 μm for bulk InGaAs to a 1.54-μm wavelength for the QW laser. This is in very good agreement with the theoretical energy shift predicted for QWs of this thickness. An intrinsic internal loss which is significantly lower than the loss observed for conventional InGaAsP lasers was demonstrated. This appears to be associated with the very low confinement factor Γ for the optical mode in the QW active layers. High differential quantum efficiency (22% facet) with weak dependence on cavity length (internal loss = 16 cm^{- 1}) and high output power (42 mW/facet) have been obtained. The low internal loss could be a useful advantage of the long-wavelength QW lasers over conventional laser diodes.