Femtosecond-Laser-Written Waveguides in Periodically Poled MgO-Doped Stoichiometric Lithium Tantalate for Frequency Conversion

Optical waveguides are often used to enhance frequency conversion efficiencies. Various types of waveguides have been applied to frequency conversion devices such as ridge and proton exchange. Recently, femtosecond laser writing technique attracted a lot of attentions, which enable 3D micromachining inside transparent materials by inducing local refractive index change [1]. Compared to conventional waveguides, the laser-written waveguides have many advantages such as keeping bulk optical damage resistance, flexible mode profile, and capability to make symmetric waveguide structure. Thus, laser-written waveguides can be used for high power and high conversion efficiency. In addition, recently, there are some demands for high power and high conversion efficiency for IR or UV generation by frequency conversion of ultrashort pulse laser with wide bandwidth for dual frequency comb spectroscopy. In order to achieve the requirements, we focused on periodically poled MgO-doped stoichiometric lithium tantalate (PPMgSLT) as a frequency conversion device, which has high optical damage threshold, high nonlinear optical coefficient and wide transparent region [2]. In this work, we developed the femtosecond-laser-written waveguides in PPMgSLT targeting the device with high power and high conversion efficiency. The waveguiding and SHG properties were characterized with a CW laser at the wavelength of 1064nm.