Lithium Niobate: The Silicon of Photonics!

Abstract

Lithium Niobate and its isomorphs (e.g. LiTaO3) is an artificial ferroelectric crystal belonging to the 3 m crystallografic group [1]. It is characterised by large pyroelectric, piezoelectric, acusto-optic, nonlinear and electro-optic coefficients features and is one of the key materials for the fabrication of integrated optical devices [2]. LiNbO3 is one of the most versatile and widely used material in photonics, with a broad range of applications ranging from acoustic-wave transducers and filters in mobile telephones, to optical modulators and wavelength converters in fibre telecommunication systems, to name just a few. Recent advances in linear and nonlinear microstructuring technologies on the LiNbO3 material platform, involving domain engineering by electric field poling techniques as well as ion-exchange processes and etching techniques, enable the fabrication of both linear and nonlinear photonic crystals as showed in Fig. 42.1. Open image in new window Fig. 42.1 View of structures for photonic applications in Lithium Niobate.(a) 1D and (b) 2D are bulk nonlinear photonic crystals for frequency doubling [3,4]; the quasi phase matching configuration is showed below.(c) and (d) show a bulk nonlinear photonic quasi-crystal and a group waveguides The possibility of periodically engineering the nonlinearity (χ (2)) of LiNbO3 in one, two dimensions or also in quasi-periodic manner by mean of electric field poling enables high conversion efficiencies in nonlinear optical interactions employing the Quasi-Phase-Matching (QPM) technique [5]. Moreover, by employing common micro fabrication or UV writing techniques is possible to fabricate surface waveguides (Fig. 42.1d) for more compact and efficient surface photonic devices.