Australian scientists create ultra-thin lens that see extremely tiny objects

A team of Australian researchers has developed a super thin, flat and lightweight lens with the ability to provide three-dimensional, or 3D, focus on even the smallest details. The lens, designed by scientists at the Swinburne University of Technology and Monash University, is 300 times thinner than a sheet of paper and is deemed a potential to revolutionise next-generation integrated optical systems used in medical diagnosis and treatment, imaging, sensing and even computing.

The team produced the lens’ thin structure by reducing graphene oxide film through a photo-reduction process. The unique refractive index of the material allows the lens to focus on small objects in a way that previous lenses have not been able to. The process used to make the ultra-thin lens is cheap and quick and easily scalable, according to the team.

“Our lens concept has a 3D subwavelength capability that is 30 times more efficient, able to tightly focus broadband light from the visible to the near infrared and offers a simple and low-cost manufacturing method,” said lead researcher Baohua Jia from Swinburne’s Centre for Micro-Photonics.

With the rapid development in nano-optics and on-chip photonic systems, the demand has increased for ultra-thin flat lenses with 3D subwavelength focusing capability, the ability to see details of an object smaller than 200 nanometres. Ordinary optical lenses work by focusing light on a specific point so the eyes can perceive it, but there is a limit to the size of objects the light can be focused on.

There had been a lot of attempts to shrink flat lenses to overcome that hurdle, but successful concepts have all been extremely complex and time-consuming to produce for real-world applications. The new lens, resulting from the study published in the journal Nature Communications, could be used to build devices capable of viewing, manipulating, monitoring and trapping the tiniest particles in real time.

The research team claims that the flexible graphene oxide lens they developed is mechanically robust and maintains excellent focusing properties under high stress. According to Professor Dan Li of the Monash Centre for Atomically Thin Material, which provided the graphene oxide film for the research, the lens paves the way for new high-tech application for graphene oxide and demonstrates how nanotechnology can add significant value to natural graphite.

The team reports that the ultra-thin lens opens up new avenues in non-invasive 3D biomedical imaging, photonic chips, aerospace photonics, micromachines and laser tweezing, which is the process of using lasers to trap tiny particles.

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