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.