Second Order Nonlinear Optical Processes in KTiOPO4 Waveguides

Abstract

Second order nonlinear optical processes have been commonly used with bulk materials for various applications such as second harmonic generation, sum and difference frequency generation, optical parametric generation and amplification, etc.[1] Most of these applications require very high input intensities to achieve reasonable conversion efficiencies and, hence, are mostly limited to use with high power laser or to resonant cavity systems.Confining the beam to an optical waveguide can significantly enhance the conversion efficiency and will require less input power. The hope is that such waveguide systems can be coupled to laser diodes to make compact visible laser sources. This paper will first discuss second order processes in waveguide systems generally, focusing on the phase matching problem and on various waveguide structures used to overcome this problem.We will then discuss the characteristics of the widely used nonlinear optical material,KTiOPO4 (KTP), including basic structure, optical waveguide fabication and domain reversal. Other materials such as LiNbO3 and LiTa03 are discussed in other lectures given at this Advanced Study Institute[2] and will not be repeated here. Finally, we will discuss the fabrication, characterization and practical limitations of several KTP optical waveguide systems designed to generate green, red, blue and uv outputs using various combinations of second harmonic and sum frequency generation.