Hannover 2016 – wissenschaftliches Programm

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Q: Fachverband Quantenoptik und Photonik

Q 9: Photonics II

Q 9.3: Vortrag

Montag, 29. Februar 2016, 15:00–15:15, f342

Laser-induced volume phase gratings in lithium niobate for noncollinear frequency conversion — •Haissam Hanafi, Dennis Niemeier, Sebastian Kroesen, Mousa Ayoub, Jörg Imbrock, and Cornelia Denz — Westfälische Wilhelms-Universität Münster, Institute of Applied Physics, Corrensstr. 2, 48149 Münster, Germany

We demonstrate the fabrication and characterization of direct femtosecond laser written volume diffraction gratings (VDG) for efficient second-harmonic generation (SHG) in x-cut lithium niobate (LiNbO₃). The designed integrated nonlinear beam splitter device allows due to it’s hybrid architecture to satisfy the noncollinear phase matching condition between the transmitted and diffracted fundamental wave within the crystal. To determine the grating period, grating thickness and refractive index change, we have measured the linear diffraction efficiency of 532 nm cw laser light depending on the incident angle and input-polarization. The nonlinear properties are analyzed by measuring noncollinear phase-matched SHG using femtosecond laser pulses with a wavelength between 1200 nm and 1400 nm. The linear as well as the nonlinear properties are investigated for a large variety of fabrication parameters of the grating, like writing speed, pulse energy, polarization, and writing direction in order to characterize the diffraction properties. Using a laser scanning SHG microscope, the structural modifications are visualized in three dimensions with high spatial resolution. Furthermore, these permanent femtosecond laser-induced gratings were systematically compared with optical erasable gratings, induced by cw laser light using the photorefractive effect in LiNbO₃:Fe.