Modulation Characteristics of Tunable Quantum-Well Heterolasers at the Radiation Frequency Tuning

Abstract

ture of nonlinear response. Introduction. At present, semiconductor lasers determine the advancements made in many fields of science and engineering. However, their radiation parameters should be further improved in accordance with new and specific requirements imposed on them by practice. For this purpose, a number of effects arising in the indicated systems should be investigated in greater detail. In particular, of great interest is the influence of the position of the radiation frequency of a laser within its amplification band on the laser modulation parameters. In this connection, the nonlinear amplitude-detuning characteristics (ADC) of injection quantum-well heterolasers have been theoretically investigated in (1-3). These characteristics reflect the dependence of the response of a laser and the modulation of its pump current on the laser radiation frequency; however, they were obtained only for certain particular cases. For example, it was suggested that the pump current remained unchanged when the radiation frequency was tuned within the limits of the amplification band. Some conclusions were also made on the basis of data obtained with the use of a single model of an active medium. The present work is devoted to investigating the behavior of the nonlinear ADCs of a laser in the case where the excess of the invariable component of the pump current over its threshold value remains unchanged when the laser radiation frequency is changed. Our investigations were performed with the use of two optical models of an active me- dium under conditions close to the experimental ones. We also investigated the multiresonance structure of the non- linear response of quantum-well heterolasers with pump-current modulation in greater detail. Main Equations and Parameters Used. For definiteness, we carried out calculations for quantum-well het- erolasers based on GaAs with quantum wells of width 5-15 nm in the active region. The dynamics of generation of a monochromatic radiation of frequency νst by such systems was described using standard equations for the density of