  Stimulated emission of sensitized Erbium atoms is reported in silicon-rich
silicon nitride waveguides. Visible pump and infrared probe measurements are
carried out in waveguides fabricated from erbium-doped silicon rich silicon
nitride. A decrease in the photoinduced absorption of the probe in the
wavelength range of the erbium emission is observed and is attributed to
stimulated emission from erbium atoms excited indirectly via the silicon excess
in an SiNx matrix. A near 50% decrease in absorption is measured, corresponding
to an 8% fraction of inverted erbium atoms. This fraction is an order of
magnitude higher than that obtained in counterpart oxide systems possessing
observable nanocrystals. Our results indicate that population inversion and
gain at 1.54 um might be possible by optimizing the silicon excess in the SiNx
matrix.
