Characterization of 8 mol% Mg-doped congruent LiTaO3 crystal for high-energy quasi-phase matching device

Abstract

Quasi-phase matching (QPM) technique have realized an efficient and various types of nonlinear wavelength conversion by using a desired nonlinear coefficient in arbitrary wavelength by specially designed crystal structure. Ferroelectric crystals such as LiNbO3 (LN) and LiTaO3 (LT) have been reported for major materials of the QPM device from visible to mid infrared (MIR) wavelength region. In last several years, we have reported a large-aperture QPM device using a Mg-doped congruent LN (MgLN) for high-power/energy operation, and demonstrated a highly efficient and high-energy optical parametric oscillation with > 0.5 J output energy by a 10-mm-thick periodically poled MgLN (PPMgLN) [1]. As increasing of both conversion efficiency and handling power/energy in PPMgLN device, crystal damage have become severe problem, which needed to find another choice for the QPM material. Compared to LN-type crystals, LT-type crystals have relatively wide transparent range, small absorption, and high thermal conductivity, although their nonlinear coefficients are low, which are suitable for high-power/energy QPM devices. LT crystal with Mg-doped stoichiometric composition, grown by double crucible Czochralski or vapor phase epitaxy method, have been already reported [2]. In this study, we focus on the Mg-doped congruent LT (MgLT) grown by conventional Czochralski method. An increase of Mg doping can basically improve various properties for the QPM device, though high-quality crystal growth become difficult. Here we focus on the characterization of 8 mol% MgLT (Mg8LT), and compare with low Mg-doped MgLTs [3] and 5 mol% MgLN.