Abstract

One of the most important device parameters of distributed- feedback (DFB) semiconductor lasers is the coupling coefficient k, which describes the strength of the coupling due to the internal diffraction grating between two counterpropagating waves. The coupling coefficient of actual devices has been determined by observing the stop-band width in below-threshold emission spectra.¹ However, this is not an easy task unless reflectivity of both the cleaved facets is sufficiently reduced (typically less than 1%). If facet reflection exists, the intrinsic emission spectrum of the DFB cavity is distorted by the Fabry- Perot (FP) cavity, which makes precise determination of the stop-band width difficult. The stop-band width becomes dependent on the positions of the facets relative to the spatial phase of the grating.

© 1993 Optical Society of America