Researchers from Tel Aviv University have developed a chip-based method to fold glass sheets into microscopic 3D photonic structures – a process called photonic origami. The technique could produce tiny, complex optical devices for data processing, sensing, and experimental physics.
“Existing 3D printers produce rough 3D structures that aren’t optically uniform and thus can’t be used for high-performance optics,” said Tal Carmon of Tel Aviv University. Inspired by pinecone scales bending to release seeds, his team used a laser-induced technique to bend ultra-thin glass sheets into ultra-smooth, transparent structures.
In Optica, the team reported record-setting 3mm-long structures just 0.5 microns thick, with less than a nanometer of surface variation. They fabricated helixes and concave and convex mirrors that reflect light without distortion. “Similar to how large 3D printers can fabricate almost any household item, photonic origami could enable a variety of tiny optical devices,” said Carmon. Potential uses include micro-zoom lenses for smartphones and light-based components for faster, more efficient computing.
The discovery happened by accident. Graduate student Manya Malhotra was asked to locate an invisible laser on glass by raising the power until it glowed – instead, the glass folded. She became the pioneering expert in photonic origami. The folding occurs when one side liquifies under laser heat and surface tension overtakes gravity, pulling the glass into a fold.
Lab engineer Ronen Ben Daniel fabricated silica glass layers on silicon chips, undercutting them with etching before folding them with CO2 laser pulses. Sheets folded in under a millisecond at speeds of 2m/s and accelerations above 2000m/s². “The level of control we had over 3D microphotonic architecture came as a pleasant surprise,” said Carmon.
The team folded sheets up to 10 microns thick into 90-degree bends and helices with precision of 0.1 microradians. They also created a microscopic glass ‘table’ with a concave cavity mirror, inspired by work from P.K. Lam of Australian National University on exploring deviations from Newtonian gravity. Starting with a sheet 5 microns thick, they patterned and folded it into a 3D structure light enough to be optically levitated. Such experiments could help probe dark matter mysteries.
“High-performance, 3D microphotonics had not been previously demonstrated,” said Carmon. “This new technique brings silica photonics – using glass to guide and control light – into the third dimension, opening up entirely new possibilities for high-performance, integrated optical devices.”