LASER ENGINEERING; Optical Feedback and Mode Selection in Semiconductor Lasers Used in Resonators with Dispersive Element

摘要

The main field of application of injection lasers is telecommunications [1]. Laser diodes are used as active elements (emitters in multichannel optical fiber links) operating as signal regenerative repeaters and sources for pumping erbium fiber amplifiers. In optical transmission and data processing systems, tunable laser diodes are used. In this case the main problems are to obtain wideband amplification (and, correspondingly, extended tuning curves) and continuous tuning with a narrow spectral emission line and no mode jumping for sufficient output power. In this paper we discuss the use of asymmetric multilayer quantum-well laser heterostructures and analyze the selective characteristics of an external resonator with diffraction grating. As an example of tunable laser emitters, we refer to asymmetric four-layer quantum-well heterostructures. In laser heterostructures of this kind, the active region contains amplifying quantum-well layers of different widths or compositions. The barrier layers are properly doped to achieve conditions for the nonuniform excitation of quantum wells. As a result, the amplification spectrum of the heterostructure becomes wider