Non-uniform strained quantum well amplifiers for multichannel optical signal amplification in the WDM system

Abstract

This paper presents a new longitudinal non-uniform compressively strained quantum well amplifier for multichannel optical signal amplification in the wavelength division multiplexing (WDM) system. Quantum transmission line modelling (Q-TLM) method is adopted to analyse the scattering spectra of electron transitions as well as the gain spectrum of QW-SOAs. It is found that the electron scattering spectrum exhibits blue shift and reduced magnitude with the decrease of carrier density while there exists red shift and enhanced magnitude with the increase of compressive strain. Furthermore, it is found that the effects of decreased carrier density on the wavelength and bandwidth of the QW-SOA gain spectrum can be compensated by increasing compressive strain. Based on the theoretical analysis, the longitudinal non-uniform (linearly and Gaussian-distributed) compressively strained quantum well amplifiers are proposed. Multichannel and dense multichannel optical signal amplification in the proposed QW-SOAs are studied and it is found that distributing non-uniform compressive strain along the quantum well amplifier cavity can effectively improve the output performance of QW-SOAs by increasing the amplification amplitude and bandwidth. The quantum well amplifier with Gaussian strain distribution has a better output spectral property for multi-channel optical signal amplification in the WDM system. These studies provide important guidance to optimize the multichannel optical signal amplification in semiconductor optical amplifiers by the band engineering.