Optically active substoichiometric Si3N4 μ-cavities

We report on the morphological and emission properties of microdisk resonators with an optically active disk material made of luminescent substoichiometric Si3N4 matrix. We demonstrate the importance of optimising the material by finding a compromise between the photoluminesce properties and optical losses. A careful design of the cavities for optimising the radiative quality factors has been also performed, enabling us to produce active disks with low intrinsic losses. Subnanometer whispering gallery mode (WGM) resonances have been experimentally detected, showing quality factors as high as 1200 around the wavelength of 719 nm. These values are among the highest previously reported values in Sinanocluster-based systems and are actually limited by the spectral resolution of our experimental setup. In addition, an increasing of the pumping flux is not generating a spectral widening of the resonances, thus not affecting the quality of the cavities. This is in contrast to what observed in other reports of Si-nc based microcavities, where significant enlargements are observed associated to carrier absorption losses