<title>Gain-coupled DFB lasers for spectroscopic application</title>

Abstract

Pure gain-coupled distributed feedback (DFB) lasers and complex-coupled DFB lasers, based on a current modulation concept is investigated. An n-doped current blocking layer is formed, either directly on top of the active region or on top of the InGaAsP index-modulation grating. The blocking layer causes a spatial modulation of the carrier concentration at the active region, forming a gain-grating. The blocking layer causes a spatial modulation of the carrier concentration at the active region, forming a gain- grating. The addition of the n-doped current blocking layer did not cause any deterioration in either the I-L or I-V curves. The stop band, which can be clearly observed in the index-coupled and the complex-coupled DFB lasers, cannot be distinguished in the pure gain-coupled DFB lasers, suggesting that the current blocking layer is sufficient to incorporate gain-coupling mechanism to the DFB lasers. The gain- and complex-coupled DFB lasers exhibit significant improvement in single model yield and susceptibility to optical feedback, compared to index-coupled DFB lasers. The concept is applied to the fabrication of DFB lasers at various wavelength from 1.3 to 1.7 micrometers .