Metasurface-based functional optical splitter for a spatially parallelized dual-polarization coherent modulator.

Area of Science:

• Photonics and Optical Engineering
• Metamaterials and Nanophotonics
• Optical Communications Technology

Background:

• Traditional dual-polarization in-phase and quadrature modulators (DP-IQMs) require complex passive optical components.
• Integrating these components efficiently is crucial for advancing optical communication systems.

Purpose of the Study:

• To propose and demonstrate a surface-normal dual-polarization in-phase and quadrature modulator (DP-IQM) using a dielectric metasurface.
• To integrate essential passive optical functionalities into a single metasurface layer.

Main Methods:

• A thin dielectric metasurface (MS) layer composed of silicon nanoposts was designed and fabricated.
• The metasurface was integrated onto a high-speed electro-absorptive modulator array.
• Experimental characterization of polarization and beam splitting functionalities was performed.

Main Results:

• The metasurface successfully integrated polarization beam splitter/combiner and interferometric circuit functionalities.
• Demonstrated polarization and beam splitting with a phase error < 0.08 rad and power imbalance < 0.9 dB.
• Achieved an error-vector magnitude < 7% for generating dual-polarization quaternary phase-shift-keying (DP-QPSK) and 16 quadrature amplitude modulation (DP-16QAM) signals.

Conclusions:

• The proposed surface-normal DP-IQM using a dielectric metasurface offers a compact and efficient solution.
• The design enables scalable two-dimensional arrays for spatially parallelized optical signal generation.
• Potential applications span optical communication, computing, and sensing.