Ti-diffused KTN waveguide enabling intensity modulation based on the quadratic electro-optic effect

Optical waveguides are fundamental components in integrated optics, enabling the confinement of light beams at micron and nanometer scales. The performance of electro-optic materials is the key to realizing waveguide-based modulation devices. Potassium tantalate niobate (KTN) crystals exhibit exceptional quadratic electro-optic effects, making them highly promising for applications in optical waveguides and electro-optic modulators. This study explored a novel, to our knowledge, optical waveguide leveraging the quadratic electro-optic effect of KTN crystals. Buried waveguides with a width of 10 μm were fabricated in KTN crystals using the titanium ion diffusion method. The impact of ion diffusion on the crystal structure of KTN was analyzed using confocal Raman spectroscopy. Based on the optical waveguide, an intensity modulator with a single waveguide and an extinction ratio of 14.2 dB at 1550 nm was developed. The modulator's different modulation functions were evaluated without and with an applied bias voltage. This research offers valuable insights for the design and production of low-driving, efficient electro-optic modulation devices in integrated optics.