Mid-Infrared Electro-Optical Modulation Using Monolithically Integrated Titanium Dioxide on Lithium Niobate Optical...

Area of Science:

• Photonics
• Materials Science
• Integrated Optics

Background:

• Mid-infrared (mid-IR) photonics requires efficient tunable devices.
• Titanium dioxide (TiO2) offers broad transparency and tunable refractive index.
• Lithium niobate (LiNbO3) possesses a strong electro-optic (E-O) Pockels effect for tunability.

Purpose of the Study:

• To demonstrate tunable photonic circuits in the mid-IR regime.
• To develop integrated TiO2-on-LiNbO3 (ToL) waveguides for E-O modulation.
• To investigate the performance of ToL waveguides for optical switching.

Main Methods:

• Fabrication of ToL waveguides using sputtered TiO2 thin films on z-cut LiNbO3 substrates.
• Characterization of waveguide optical properties and E-O modulation.
• Analysis of the hybrid mode profile and its dependence on TiO2 ridge height.

Main Results:

• Achieved sharp waveguide modes at 2.5 µm without scattering or distortion.
• Measured an effective E-O coefficient (γeff) of 5.9 pm/V, approaching the bulk LiNbO3 value.
• Demonstrated a hybrid mode profile tunable by adjusting the TiO2 ridge height.

Conclusions:

• Monolithically integrated ToL modulators are efficient, small-footprint optical switches.
• ToL waveguides are promising for developing reconfigurable photonic integrated circuits in the mid-IR.
• The demonstrated technology enables advanced functionalities for mid-IR photonic applications.