Observation of second harmonic emission and three-photon fluorescence from Gallium-Nitride

Abstract

In this study, optical emission from the undoped GaN epilayer sample was characterized using confocal micro-spectroscopy. A femtosecond laser was used to excite the sample. As the laser wavelength tuned from 762-796nm, the sample emitted a corresponding second harmonic signal from 381-398nm with a quadratic power dependence. A strong signal at 367nm resulted from a three-photon process with cubic power dependence was simultaneously observed for the first time.