Aluminum Shield Method Traps Light for Millions of Cycles
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- Aalto University researchers and international collaborators developed a "nanoscale surgery" fabrication method that coats van der Waals (vdW) materials with a thin aluminum shield before focused ion beam carving, achieving sub-100-nanometer precision without damaging the crystal lattice.
- The shielded approach produced ultra-smooth vdW microdisk resonators with quality factors above 1,000,000, meaning only about one part per million of light is lost per cycle — letting light circulate millions of times before fading.
- Professor Zhipei Sun of Aalto said this performance surpasses previous vdW resonant systems by three orders of magnitude, calling it "a dramatic advance for the field."
- Second harmonic generation efficiency in the devices rose by four orders of magnitude, or roughly 10,000 times, compared with prior vdW records, because the tightly confined light interacts far more strongly with the material.
- The work, published in Nature Materials (2026), repositions vdW materials from passive coatings toward active building blocks for reconfigurable photonic circuits, quantum light sources, and highly sensitive on-chip optical sensors.
- Researchers Xiaoqi Cui and Andreas Liapis framed standard nanofabrication as "too aggressive" for atomically thin vdW layers, with Liapis likening the aluminum coating to a "microscopic suit of armor" that absorbs the ion beam's destructive impact.
Why it matters: The aluminum-shielded fabrication method converts vdW materials from passive coatings into active photonic and quantum device building blocks, with million-cycle light trapping directly enabling a 10,000-fold jump in second harmonic generation efficiency — unlocking on-chip reconfigurable photonic circuits, quantum light sources, and highly sensitive optical sensors that were previously blocked by fabrication damage.
