Photonic Origami Creates Microscopic Glass Structures
Researchers have reportedly devised a way to use a laser to fold sub-micrometer-thick glass sheets directly on a chip (Optica, doi: 10.1364/OPTICA.560597). Discovered by accident, the technique could enable the creation of microscopic and complex optical devices for data processing, sensing and experimental physics.
A serendipitous discovery
Constructing high-quality silica photonic structures at the nanoscale with existing 3D-printing techniques is challenging because surface roughness—a result of 3D printing—can cause scattering losses, drastically degrading optical performance. This challenge was not front of mind, however, when Tal Carmon, Tel Aviv University, Israel, asked his graduate student Manya Malhotra to point a laser at glass, with increasing power, until the spot glowed.
Carmon was only hoping to identify the exact location where the invisible laser light was hitting the surface, but then the glass folded. “It was exciting to see the folding silica under the microscope,” said Carmon.
Folding glass
With the new technique, which is reminiscent of origami, the team is able to manipulate ultrasmooth silica on silicon chips with 20-nm alignment accuracy into polylines and helices. To prepare the glass for folding, Carmon, Malhotra and colleagues thermally grow a very smooth (down to 0.5 μm) amorphous silica layer on top of a silicon chip with cleanroom-grade silicon and oxygen. They then release the silica from the silicon with dry xenon difluoride silicon etching. Now, the glass surface is ready to be folded.
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