Enhanced wavelength shift in partly gain-coupled distributed feedback lasers using quantum well intermixing

Abstract

In this paper, we present a theoretical study on the properties of wavelength shift due to quantum well (QW) intermixing in the partly gain-coupled distributed feedback (DFB) lasers. A maximum possible wavelength red-shift of 9.2 nm is predicted if using a proper DFB grating, whose period is smaller than that in the conventional DFB lasers. In contrast to the index-coupled λ/4-shifted DFB lasers, no increase in carrier density is required to compensate for the gain reduction due to QW intermixing, as the threshold gain in the partly gain-coupled DFB laser decreases with the QW intermixing because of the increase in the coupling coefficient. The injected threshold current density for lasing is considerably flat in the wavelength red-shift range. The result is important as it indicates that the QW intermixing technique may be used in the fabrication of the equal threshold DFB lasers with different wavelengths in the monolithically integrated laser arrays.