Abstract: An IAU laser is stabilized to reduce intensity fluctuations. The laser comprises an IAU gain medium disposed in an optical resonance cavity and a multiphoton absorbing medium disposed in the cavity to reduce intensity fluctuations. A pump source to excite the gain medium is coupled to the cavity. In operation, the multiphoton absorbing material absorbs primarily at high intensity levels, effectively increasing the loss at high intensities. In an advantageous embodiment, the active medium comprises erbium-doped glass and the multiphoton absorber comprises a body of semiconductor exhibiting two-photon absorption at the emission wavelength.