Large linewidth-enhancement factor in a microchip laser

Abstract

We evidence experimentally that the linewidth-enhancement factor $\ensuremath{\alpha}$ can take a rather large value ($\ensuremath{\alpha}\ensuremath{\approx}1$) for a nonsemiconductor laser, here a ${\mathrm{Nd}}^{3+}$: YAG microchip laser. This measure is performed using an original and simple method adapted to this kind of laser and based on the variations of the laser relaxation frequency when the laser is subjected to an optical feedback.