PUBLICATION SPOTLIGHT
Highlights
- Published in Light: Science & Applications (Nature portfolio), 2025 — already 3 citations
- ICP-200 fabricated silicon nanopillars using C₄F₈/SF₆ at 500 W ICP power with precise etch control
- First fully non-invasive, two-dimensional quantitative visualization of transparent flow fields using metasurfaces
- Applications in fluid physics, industrial design, gas leak detection, and 3D morphology reconstruction
The Research
A team from Nanjing University has published a study in Light: Science & Applications presenting the first non-invasive, fully two-dimensional quantitative visualization of transparent flow fields using photonic spin-decoupled metasurfaces.
Transparent flow fields — such as airflow around aerodynamic structures or gas plumes — are invisible to conventional cameras. Existing visualization methods either disturb the flow (particle tracers) or provide only one-dimensional information. This metasurface-based approach captures density gradient information in both horizontal and vertical dimensions simultaneously, enabling real-time quantitative derivation of multiple physical parameters from a single measurement.
The researchers demonstrated the system across diverse scenarios including temperature field mapping, gas leak detection, visualization of fluid physical phenomena (laminar flow, turbulence, vortices), and 3D morphological reconstruction of transparent phase objects.
Reference:
Fan, Q. et al., "Non-invasive and fully two-dimensional quantitative visualization of transparent flow fields enabled by photonic spin-decoupled metasurfaces," Light: Science & Applications 14, 113 (2025).
DOI: 10.1038/s41377-025-01793-2
The Role of Plasma Etching
The ICP-200 Inductively Coupled Plasma Etching System (Tailong Electronics) was used to fabricate the silicon nanopillar arrays that form the photonic spin-decoupled metasurface.
Process Parameters
| Parameter | Value |
|---|---|
| Equipment | ICP-200 (Tailong Electronics) |
| Process | Silicon nanopillar dry etching |
| Gas Chemistry | C₄F₈ / SF₆ (ratio 2.5:1) |
| ICP Power | 500 W |
| Bias RF Power | 40 W |
| Chamber Pressure | 13 mTorr |
Why These Parameters Matter
The metasurface requires silicon nanopillars with precisely controlled height (h) and period (P) to achieve the designed Jones matrix response for photonic spin-decoupling. The ICP-200\'s high-density plasma (500 W ICP) combined with low bias power (40 W) enables:
- High-aspect-ratio etching of silicon nanopillars with vertical sidewalls
- Minimal substrate damage from the low bias power, preserving the optical quality of the underlying Si₃N₄ substrate
- Uniform etch profiles across the entire metasurface array — critical for consistent optical phase control
The C₄F₈/SF₆ chemistry at 2.5:1 ratio provides a balanced etch/passivation process: SF₆ drives the silicon etch while C₄F₈ provides sidewall passivation to maintain vertical profiles.
Figure 1: Metasurface Flow Visualization — photonic spin-decoupled metasurface enables non-invasive 2D visualization of transparent flow fields
Key Results
| Metric | Value |
|---|---|
| Visualization dimensions | Simultaneous 2D (horizontal + vertical gradients) |
| Measurement mode | Real-time quantitative, single acquisition |
| Invasiveness | Fully non-invasive (no tracers/particles) |
| Citations | 3 (since 2025 publication) |
Demonstrated Applications
- Temperature field mapping — real-time visualization of thermal plumes and heat sources
- Gas leak detection — spatial identification and quantification of gas releases
- Fluid dynamics research — visualization of laminar flow, turbulence, and vortex structures
- 3D reconstruction — morphological imaging of transparent objects (e.g., optical lenses)
- Industrial inspection — non-contact quality control and flow monitoring
Equipment Used
- ICP-200 — Inductively Coupled Plasma Etching System for silicon nanopillar fabrication
- Manufacturer: Beijing Zhongke Tailong Electronics Co., Ltd.
- Available through NineScrolls: View ICP Etcher Series →
Takeaway
This work — already accumulating citations since its 2025 publication — demonstrates the ICP-200\'s ability to fabricate demanding high-aspect-ratio silicon nanostructures with the precision required for advanced metasurface optics. The combination of high ICP power and low bias enables the vertical sidewall profiles essential for polarization-sensitive metasurfaces.
Together with the color router paper (also in Light: Science & Applications), this represents two Nature-portfolio publications in rapid succession featuring Tailong Electronics etching systems — a strong endorsement of equipment performance for the nanophotonics community.
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Related Articles
- On-Chip Metasurface Color Router — another metasurface application using RIE-150A dry etching
- ICP‑RIE Technology — high-density plasma for advanced etching
References
- Fan, Q. et al., "Non-invasive and fully two-dimensional quantitative visualization of transparent flow fields enabled by photonic spin-decoupled metasurfaces," Light: Science & Applications 14, 113 (2025). doi:10.1038/s41377-025-01793-2