RIE-150A Enables On-Chip Metasurface Color Router

By NineScrolls Engineering · 2026-01-12 · 6 min read · Publication Spotlight

PUBLICATION SPOTLIGHT

Highlights

• Published in Light: Science & Applications (Nature portfolio), 2026
• RIE-150A performed precision Cr-to-Si pattern transfer using SF₆/CHF₃/O₂ gas chemistry
• The on-chip q-BIC metasurface achieves wavelength-selective color routing with near-unity energy utilization efficiency
• Applications in WDM, wearable displays, and integrated photonic systems

The Research

A team from Wuhan University has published a study in Light: Science & Applications — one of the highest-impact optics journals in the Nature portfolio — demonstrating an on-chip nonlocal metasurface color router that overcomes the fundamental energy-loss limitation of conventional spatial-multiplexing approaches.

By leveraging symmetry-broken quasi-bound states in the continuum (q-BICs), the researchers achieved wavelength-selective extraction and routing of guided waves into free space. Through precise engineering of on-chip meta-diatom pairs with controlled scaling and asymmetry, they simultaneously modulated both extraction intensity and narrowband spectral extraction (~20 nm bandwidth). The result is a cascading multiplexing scheme that achieves near-unity energy utilization efficiency (EUE), far exceeding the ~33% theoretical limit of conventional free-space spatial multiplexing.

Reference:
Shi, Y. et al., "On-chip nonlocal metasurface for color router: conquering efficiency-loss from spatial-multiplexing," Light: Science & Applications 15, 66 (2026).
DOI: 10.1038/s41377-025-02146-9

The Role of Plasma Etching

The RIE-150A Reactive Ion Etcher (Beijing Zhongke Tailong Electronics Co., Ltd.) was used in a critical fabrication step to define the metasurface nanostructures.

Process Details

Fabrication Flow

The metasurface consists of pairs of tilted α-Si nanoblocks (height: 380 nm) on a Si₃N₄ planar waveguide (220 nm) atop a SiO₂ substrate. The fabrication process included:

1. PECVD deposition of Si₃N₄ waveguide and α-Si layers
2. Electron beam lithography to define meta-diatom patterns in PMMA resist
3. Cr mask deposition and lift-off
4. RIE-150A etching — SF₆/CHF₃/O₂ gas mixture transferred the Cr patterns into the α-Si layer with high fidelity
5. Cr mask removal with chemical etchant

The RIE-150A\'s role was critical because the metasurface\'s optical performance depends directly on the precision of the nanoscale etching. The tilting angle θ and scaling factor S of the meta-diatom pairs must be accurately reproduced to achieve the designed q-BIC resonance conditions and spectral selectivity.

Figure 1: q-BIC metasurface color routing — cascading meta-diatom pairs achieve wavelength-selective extraction with near-unity energy utilization

Key Results

Demonstrated Applications

• On-chip wavelength-division multiplexing (WDM) — selective routing of different wavelengths to distinct spatial positions
• Multicolor meta-displays — vibrant color arrays encoding both spectral and intensity information
• Cascading color routers — multiple q-BIC pixels cascaded along a waveguide for complex routing

Equipment Used

• RIE-150A — Reactive Ion Etcher for α-Si nanostructure patterning
• Manufacturer: Beijing Zhongke Tailong Electronics Co., Ltd.
• Available through NineScrolls: View RIE Etcher Series →

Takeaway

Publication in Light: Science & Applications (Nature portfolio, Impact Factor ~20) represents the highest tier of visibility in optics and photonics. This work demonstrates the RIE-150A\'s capability to deliver the nanoscale pattern fidelity required for advanced metasurface devices where sub-nanometer dimensional control directly determines optical performance.

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References

1. Shi, Y. et al., "On-chip nonlocal metasurface for color router: conquering efficiency-loss from spatial-multiplexing," Light: Science & Applications 15, 66 (2026). doi:10.1038/s41377-025-02146-9