Abstract

The linewidth-enhancement factor a determines the spectral linewidth and frequency chirping under high-speed modulation in semiconductor lasers.^1,3 The spectral purity and the frequency chirping of the semiconductor lasers are important in their application to optical communication systems. In a recent experimental study we found that the spectral linewidths of quantum-well (QW) lasers are strongly affected by the quantum-well barrier height in the QW structure.⁴ We have attributed this phenomenon to the fact that the linewidth-enhancement factor a is significantly influenced by the inevitable thermal population of injected carriers in the optical confining region, which contributes to α through the dominant interbandtransition component and the subordinate free-carrier component of the amplitude-phase coupling in the QW lasers. Here we report on the direct measurement of the dispersion of the a parameter in QW lasers with different quantum-well barrier heights.

© 1993 Optical Society of America