Okinawa group develops image analysis method for microcavities – without damage

10 Nov 2025

X-ray µCT opens route to exploring 3D “wave chaos”, nonlinear optics, and quantum photonics.

In the world of optics, tiny structures called microcavities – often no wider than 100 μm – play a crucial role in technologies ranging from lasers to sensors. These microscopic resonators trap light, allowing it to circulate millions of times within their boundaries.

When perfectly shaped, light inside them moves in smooth, circular paths. But when their symmetry is slightly disturbed, the light begins to behave unpredictably, following chaotic routes that can lead to surprising effects like one-way laser emission or stronger light–matter interactions.

Until now, most research on this chaotic behavior has focused on flat, two-dimensional microcavities. These are easier to study because their shape can be seen and measured under a microscope.

3D microcavities remained unexplored

But truly 3D microcavities – in which deformation occurs in all directions – have remained largely unexplored. Their internal geometry is difficult to capture without cutting or damaging the sample, making it hard to understand how light behaves inside them.

A new study published in Advance Photonics Nexus is claimed to change all that. An international team of researchers, led by at Okinawa Institute of Science and Technology Graduate University (OISTGU), Japan, has developed a way to image and analyze 3D chaotic microcavities without harming them.

They use X-ray microcomputed tomography (µCT), a technique commonly found in medical and materials science labs, to scan a slightly deformed silica microsphere. This allows them to reconstruct its full 3D shape with submicron precision.

With this detailed model, the team can calculate how light travels through the deformed cavity. They have found that when the shape is distorted in multiple directions, the light does not just bounce around randomly – it spreads throughout the entire cavity in a process known as Arnold diffusion. This confirms a long-standing theoretical prediction about 3D chaotic light dynamics.

According to Professor Síle Nic Chormaic, corresponding author on the report and director of the Light-Matter Interactions for Quantum Technologies Unit at Okinawa, “This work opens a new window for exploring 3D wave chaos, nonlinear optics, and quantum photonics. Beyond fundamental studies, the approach could inspire new designs for high-sensitivity sensors, broadband microlasers, and complex optical networks that harness chaotic dynamics for enhanced performance.”

The ability to measure and predict light behavior in these complex structures opens new possibilities for both fundamental science and practical applications.

• This article was first published on spie.org.