Spectral linewidth broadening due to self-modulation of the refractive index of semiconductor lasers

We propose a new mechanism for the spectral linewidth broadening of semiconductor lasers, which is self-modulation of the refractive index of the semiconductor cavity caused by interference between the lasing modes. It is shown that the broadening of the main-mode linewidth due to submodes is explained reasonably well by the self-modulation term. A new interpretation of the power-independent linewidth problem is also suggested.