Nonlinear optical properties of AlN thin films characterized by the Nonlinear elliptical polarization rotation technique

Aluminum nitride (AlN) thin films were deposited on glass substrates and analyzed for their potential in integrated nonlinear photonics. The material features a wide bandgap (6.2 ± 0.05 eV), an infrared refractive index of 2.00 ± 0.05, and full CMOS compatibility, making it well-suited for on-chip devices. AFM and Raman spectroscopy confirmed a uniform morphology and amorphous structure with a thickness of approximately 350 nm. The nonlinear optical response, examined through the nonlinear elliptical polarization rotation (NER) technique, showed a third-order nonlinearity approximately fifteen times higher than fused silica, confirming AlN’s potential for efficient integrated photonic applications.