Second order optical nonlinearities of radio frequency sputter-deposited AlN thin films

Polarized second harmonic generation measurements were performed on AlN films deposited on (100) sapphire substrates by the reactive rf sputtering technique. The bulk effective second order nonlinearity observed in these films is typically about 6×10−9 esu at 1.06 μm, several times larger than that of quartz or KTP. The tensorial properties of the nonlinearity are consistent with the crystal symmetry of AlN and the microcrystallinity of these films.