Nonlinear optical waveguides inscribed by fs-laser in organic crystal for broadband second harmonic generation of UV pulses

Abstract

Optical waveguides are main components for the development of integrated photonic devices, not only for allowing light guidance but also for their ability to act as nonlinear optical elements. Direct laser writing with ultrashort pulses has provided considerable advances in the fabrication of 3D waveguides and the improvement of its optical properties. Nonetheless, such progresses have been achieved for waveguides designed in inorganic materials and little attention has been devoted to organic crystals, which offer new perspectives for the field. In this direction, this paper describes the fs-laser inscription of cladding waveguides in an amino acid crystal, with guiding losses on the order of 0.5 dB/mm at visible and infrared regions. Such waveguides are able to act as active nonlinear optical elements, supporting broadband second harmonic generation centered at 377 nm, with a normalized power conversion efficiency of (10.3 ± 0.4) % (MW cm2)−1. Its normalized intensity conversion efficiency was greater than the one for the crystal itself, probably due to the influence of the waveguide dispersion contribution on the phase matching condition.