News | October 15, 2025

Laser-Induced 'Photonic Origami' For Optical Devices

A novel, CO, laser-pulse technique can precisely fold ultra-thin glass sheets to create microscopic 3D photonic structures directly on a silicon chip.

The ‘photonic origami’ chip-based technique pinpoints opportunities to create ultra-smooth, high-performance glass structures for next-generation data, sensing and physics applications, according to scientists at Tel Aviv University, Israel, who chanced on the discovery by accident.

They also report to have created an ultra-light, compact table to explore possible deviations from Newtonian gravity.

According to research lead Tal Carmon, the initial thinking was based on his realisation that inherently planar on-chip 2D structures could potentially be folded into '3D architectures that contain ultra-transparent resonators and smooth concave mirrors'.

Graduate student Manya Malhotra then stumbled across the ‘photonic origami’ technique while trying to pinpoint where an invisible laser beam was striking ultra-thin glass sheets. As she increased the CO laser pulse’s intensity, the sheets unexpectedly folded in addition to the anticipated glow.

The explanation for this behaviour lies in how the glass liquefies when one side is heated by laser pulses. As the surface tension increases and becomes stronger than gravity, the spot where the laser strikes makes the glass fold precisely, say the scientists.

Taking this discovery forward, lab engineer Ronen Ben Daniel fabricated a thin layer of silica glass on a silicon chip and shaped the material into a 2D form. Next, etching undercut the silicon underneath the glass sheet while a small support section remained to hold the sheet in place.

By directing the CO laser beam at the thin glass-mounted sheets, the team reports that the material can fold in less than a millisecond and at a speed of 2m/s with acceleration exceeding 2,000m/s².

Next, they adapted another folding technique to curve 3mm-long structures into an arc just 500nm thick.

'The silica is first grown on silicon at a very high temperature,' explains Carmon on the modified method. 'When cooling, an internal stress appears in the silica due to the different thermal expansion coefficient of the silica bar relative to the silicon substrate. When the silicon is etched, silica bends due to the stored stress. For thicker structures, we heat one side of the bar with a laser, melting it down. Then the surface tension bends the bar.'

Measuring about 1/200th the width of a human hair, the researchers say these structures set a record length-to-thickness ratio for 3D structures.

After undertaking further work to create microscopic structures, they can bend glass sheets measuring up to 10µm in thickness into shapes that range from 90o knee to helices, and all achieved with fine control.

The work also includes the fabrication of helix shapes. These are generated by focusing the laser on a silica bar and moving it at a constant speed to create a continuously moving knee. Surface tension bends the bar at the melted region.

The work was inspired by PK Lam’s 2013 research on Scattering-free optical levitation of a cavity mirror. This suggests exploiting multiple reflections of light between a pair of optically levitated cavity mirrors to explore potential deviations from Newtonian gravity at a miniscule scale. The team at Tel Aviv University fabricated an ultra-light compact table from a glass sheet only 5µm thick.

By using the laser technique to fold the 3D table using a concave mirror at its base, the researchers say their method could be used for optically levitated experiments to uncover mysteries in gravity’s behaviour at short range.

Source: Institute of Materials, Minerals and Mining