Engineering of 2D and 3D holographic gratings in photorefractive media

Abstract

The formation of 2D and 3D photonic lattices by Bessel standing wave and combined interferometric-mask techniques is performed with the use of cw 532 nm laser beam in photorefractive lithium niobate crystal doped with Fe and Fe, Cu impurity ions. The non-uniform intensity distribution of the beams is imparted into the irradiating photorefractive medium via electro-optic effect thus creating micro- and nano-scale 2D and 3D refractive index gratings with new symmetries and properties. Non-diffracting Bessel standing wave technique provides the recording of high contrast 2D photonic lattices which is the combination of annular and planar gratings with the period of ~9 μm in radial direction and half-wavelength period of 266 nm in azimuthal direction. The created by combined interferometric-mask technique 3D photonic lattices can be represented as numerous mask-generated 2D quasi-periodic structures located in each antinode of the standing wave. The formed 3D gratings have ~ 30 μm period in radial and azimuthal directions and 266 nm in axial direction. The 2D and 3D gratings were interrogated by diffraction of low intensity Gaussian probe beams from the recorded structures, as well as by direct observation by phase microscope.