Electro-absorption modulator configuration integrated with Ti diffused waveguide in lithium niobate

Lithium niobate (LiNbO 3 ) remains a prominent material in integrated photonics due to its excellent electro-optic characteristics. Titanium diffused waveguides on LiNbO 3 substrates facilitate efficient single-mode light coupling, particularly at the 1.55 μm telecom wavelength. Despite their advantages, conventional modulators built on this platform often exhibit substantial footprints, limiting large-scale photonic integration. This paper introduces a compact electro-absorption modulator design that utilizes an ITO/SiO 2 /Au multilayer stack with an overlaid TiO 2 film atop a Ti-diffused waveguide. The high-index TiO 2 layer shifts the optical mode profile closer to the surface, enhancing interaction with the active ITO layer. Simulations predict an extinction ratio of 3.75 dB within a 20 μm device length, corresponding to a modulation efficiency of 0.19 dB/μm and an insertion loss of 2.1 dB. Materials-level validation of the ITO/SiO 2 /metal Metal-Oxide-Semiconductor (MOS) electro-absorption mechanism is presented using an ITO-coated rutile prism, demonstrating an extinction ratio of 5.1 dB with a 3 dB bandwidth of 1.1 kHz.