High performance B-spline multimode waveguide bends in lithium niobate on insulator.

Area of Science:

• Integrated Photonics
• Materials Science
• Waveguide Optics

Background:

• Lithium niobate on insulator (LNOI) is a key material for integrated photonics.
• Traditional LNOI waveguide bends suffer from high losses and mode mismatch.
• Developing efficient multimode waveguides is crucial for advanced photonic circuits.

Purpose of the Study:

• To introduce and evaluate B-spline curves for optimizing multimode waveguide bends in LNOI.
• To address challenges of insertion loss (IL) and mode crosstalk (CT) in LNOI waveguide designs.
• To enable high-performance multimode waveguides for LNOI photonic integrated circuits.

Main Methods:

• Utilizing B-spline curves for flexible and precise control of waveguide bend curvature.
• Simultaneous optimization of insertion loss and mode crosstalk.
• Experimental validation of 90° B-spline-based waveguide bends on LNOI.

Main Results:

• Achieved ultra-low insertion losses: 0.05 dB (TE0), 0.10 dB (TE1), and 0.29 dB (TE2).
• Demonstrated mode crosstalk below -16.71 dB across all modes for cascaded bends.
• B-spline curves provide superior design flexibility and smooth transitions.

Conclusions:

• B-spline-based designs offer a promising solution for high-performance multimode waveguides in LNOI.
• This approach effectively mitigates key challenges in LNOI photonic integrated circuits.
• The findings pave the way for advanced LNOI-based photonic devices.