Metastructure-enabled scalable multiple mode-order converters: conceptual design and demonstration in direct-access...

Area of Science:

• Photonics
• Nanotechnology
• Optical Communications

Background:

• Advancements in multimode photonic technologies require on-chip multiple mode-order converters (MMOCs).
• Existing MMOCs suffer from limited traffic capacity, polarization dependence, and scalability issues.

Purpose of the Study:

• To propose a novel, highly scalable MMOC design framework.
• To enable efficient manipulation of higher-order modes for advanced optical applications.

Main Methods:

• Integration of subwavelength grating (SWG) metastructures into taper-tailored multimode waveguides.
• Synergistic use of coherent scattering and beam shaping for mode excitation and phase control.
• Metastructure optimization for specific mode manipulation requirements.

Main Results:

• Achieved low insertion losses (< 1.85 dB) and crosstalk (< -12.5 dB) across significant bandwidths (22 or 50 nm).
• Demonstrated polarization-independent quad-mode operation.
• Pioneered simultaneous dual-pair mode exchange (TE0↔TE2 and TE1↔TE3), doubling efficiency.
• Integrated into a direct-access mode add/drop system (DAMAD) for TE0/TE1 dual-mode operations with ILs < 4.5 dB and CTs < -15.5 dB.
• Confirmed high-speed capability with clear eye diagrams at 32/64 Gbps.

Conclusions:

• The proposed SWG-based MMOC design framework offers a scalable and efficient solution for on-chip mode manipulation.
• This technology has transformative potential for higher-order mode-based optical communications and integrated photonic circuits.