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Published online by Cambridge University Press: 15 March 2011
We report electro-optic performance of highly polar axis oriented Na0.5K0.5NbO3(NKN) films grown directly on Pt(100nm)/Ti(10nm)/SiO2/Si(001) substrates by rf-magnetron sputtering. Semitransparent gold electrodes (diameter Ø= 2 mm) were deposited ontop the NKN films by a thermal evaporation through the contact mask. Processing parameters have been specially optimized to obtain “electrosoft” NKN films with a non-linear fatigue-free P-E characteristics: low remnant Pr = 3.6 μC/cm2 and high induced polarization P = 26 μC/cm2 @ 522 kV/cm, and the coercive field Ec= 39 kV/cm. Electro-optical characterization of NKN/Pt/Si films has been performed using waveguide refractometry: a free-space coupling of a light beam into the thin-film waveguide modes. Intensity of TM- andTE-polarized light of 670 nm laser diode reflected from the free surface of NKN film and Au-cladding NKN/Pt/Si waveguide was recorded at zero and 30 V (100 kV/cm) bias electric field. Extraordinary and ordinary refractive indices as well as electro-optic coefficient have been determined by fitting these experimental data to the Fresnel formulas. Applying 160 V (530 kV/cm) across the parallel plate NKN capacitor (Ø= 2 mm, thickness 3 μm), modulation of the reflected light as high as 40% was achieved.