Australian scientists have achieved the previously unachievable – they’ve worked out a way to zoom in closer on an object than ever before. While that’s the easiest way to understand the microscope breakthrough, there’s so much more to the work physicists at the University of Sydney have been doing.
There are physical limits to how closely we can examine an object using traditional optical methods, which the uni tells us is a barrier known as the ‘diffraction limit’. They said it is determined by the fact that light manifests as a wave. It means a focused image can never be smaller than half the wavelength of light used to observe an object.
Attempts to break this limit with “super lenses” have all hit the hurdle of extreme visual losses, making the lenses opaque. Here’s where the work from the university’s physicists comes in: They’ve shown a new pathway to achieve superlensing with minimal losses, breaking through the diffraction limit by a factor of nearly four times.
The key to their success, they said, was to remove the super lens altogether.
“The work should allow scientists to further improve super-resolution microscopy,” the press release making the announcement explained. “It could advance imaging in fields as varied as cancer diagnostics, medical imaging, or archaeology and forensics.”
According to lead author of the research, Dr Alessandro Tuniz from the School of Physics and University of Sydney Nano Institute, the team has developed a practical way to implement superlensing, without a super lens.
“To do this, we placed our light probe far away from the object and collected both high- and low-resolution information. By measuring further away, the probe doesn’t interfere with the high-resolution data, a feature of previous methods,” he said, adding that previous attempts have tried to make super lenses using novel materials. However, most materials absorb too much light to make the super lens useful.
“We overcome this by performing the superlens operation as a post-processing step on a computer, after the measurement itself. This produces a ‘truthful’ image of the object through the selective amplification of evanescent, or vanishing, light waves.”
Superlensing attempts have previously focused on high-resolution information, but this data decays exponentially with distance and is quickly overwhelmed by low-resolution data – moving the probe so close to an object also distorts the image. The team has moved their probe further away and as a result can maintain the integrity of the high-resolution information and use a post-observation technique to filter out the low-resolution data.
“This technique is a first step in allowing high-resolution images while staying at a safe distance from the object without distorting what you see,” Tuniz said. “Our technique could be used at other frequency ranges. We expect anyone performing high-resolution optical microscopy will find this technique of interest.”
The research is published today in Nature Communications.
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