Nonlinear mode coupling in Er,Yb:glass microchip lasers

Summary form only given. Coupling between laser modes is a crucial phenomenon when single-frequency operation is desired in Er,Yb:glass microchip lasers. For instance, Taccheo et al. (see Opt. Lett., vol.20, p.889, 1995) have obtained single longitudinal mode operation of a laser with a net gain bandwidth 10 times larger than the cavity free spectral range. Furthermore, single polarization oscillation may be obtained in spite of the inherent cylindrical symmetry of the system. These results raise the question of the coupling strength between modes in these lasers. Consequently we develop here an experimental technique to investigate the coupling between either longitudinal modes or polarization eigenstates in such microchip lasers.