Deep-subwavelength waveguide taper with adiabatic-like performance based on epsilon-near-zero materials

Area of Science:

• Photonics
• Metamaterials
• Waveguide technology

Background:

• Efficient light coupling between dissimilar waveguides is crucial for integrated photonics.
• Existing methods often struggle with miniaturization and impedance matching challenges.
• Epsilon-near-zero (ENZ) materials offer unique electromagnetic properties for novel device designs.

Purpose of the Study:

• To propose and validate an ultracompact waveguide taper design using ENZ media.
• To establish a unified framework for coupling diverse waveguides, including impedance-mismatched scenarios.
• To achieve adiabatic-like mode evolution at deep-subwavelength dimensions.

Main Methods:

• Development of a unified design framework for waveguide coupling.
• Utilizing epsilon-near-zero (ENZ) media for passive impedance matching.
• Employing non-Hermitian designs for unidirectional reflectionless transport.
• Implementing cascaded passive configurations for bidirectional coupling.
• Conducting full-wave simulations with a 3D cutoff-waveguide model.

Main Results:

• Demonstrated ultracompact waveguide tapers enabling adiabatic-like mode evolution at deep-subwavelength scales.
• Achieved reflectionless performance with extreme miniaturization.
• Validated efficient coupling for both matched and mismatched characteristic impedances.
• Confirmed low-loss transmission and practically viable structures.

Conclusions:

• The proposed ENZ-based waveguide tapers offer a scalable solution for high-density photonic integration.
• The design framework effectively addresses challenges in coupling dissimilar waveguides.
• The technology enables significant miniaturization while maintaining high performance.