EO properties and photorefractive two-beam coupling in AlN at 375 nm

Abstract

Aluminium nitride (AlN) is a wide bandgap semiconductor with an intrinsic band-to-band absorption edge at ∼200 nm wavelength. Therefore, the material is promising for optical use in the ultraviolet region. With a wurtzite-type, noncentrosymmetric crystal structure, AlN is also interesting for second order nonlinear optics and electro-optics. As grown crystals of AlN show relatively large absorption starting below 650 nm. With the material properties of AlN supporting the photorefractive effect we examined AlN as a photorefractive beam coupler. No effect was observed in the visible spectral range. Using the UV wavelength of 375 nm, where the absorption constant is (17 ± 2) cm-1 for the extraordinary polarization beam coupling was realized. The results show relatively weak and slow photorefractive effect.