Heuristic approach to spontaneous emission factor of gain-guided lasers

The problem of the spontaneous-emission coupling into the lasing mode of a gain-guided semiconductor laser is addressed using a heuristic approach based on the notion of the angular-spectrum width. By using physical arguments, it is shown that a gain-guided laser has enhanced contribution from spontaneous emission simply because it has wider lateral angular spectra and far fields compared with those obtained for an index-guided laser. In contrast to previous work, here much lower values of the enhancement factor are predicted.