Tag Archives: optical microscope

Extreme optical imaging at Griffith University (Australia) reveals a single atom’s shadow

The July 3, 2012 news item on Nanowerk provides a rather intriguing opening line and image,

A pixelated image of a black spot on an orange background isn’t likely to win any photographic competitions.

But the seemingly bland image, taken by scientists at Queensland’s Griffith University, could potentially revolutionise mankind’s understanding of physics and how the world works.

Artist’s illustration of a single atom shadow. (Image: Kielpinski group, Griffith University)

On checking, I found the following image, which helped clarify for me the shadow’s location,  alongside Helen Wright’s July 3, 2012 news item for Griffith University.

In an international scientific breakthrough, a Griffith University research team has been able to photograph the shadow of a single atom for the first time. (from Griffith University)

Here’s more from Wright news item,

“We have reached the extreme limit of microscopy; you cannot see anything smaller than an atom using visible light,” Professor Dave Kielpinski of Griffith University’s Centre for Quantum Dynamics in Brisbane.

“We wanted to investigate how few atoms are required to cast a shadow and we proved it takes just one,” Professor Kielpinski said.

I was quite interested in the description of the process that Wright provides,

At the heart of this Griffith University achievement is a super high-resolution microscope, which makes the shadow dark enough to see. No other facility in the world has the capability for such extreme optical imaging.

Holding an atom still long enough to take its photo, while remarkable in itself, is not new technology; the atom is isolated within a chamber and held in free space by electrical forces.

Professor Kielpinski and his colleagues trapped single atomic ions of the element ytterbium and exposed them to a specific frequency of light. Under this light the atom’s shadow was cast onto a detector, and a digital camera was then able to capture the image.

“By using the ultra hi-res microscope we were able to concentrate the image down to a smaller area than has been achieved before, creating a darker image which is easier to see,” Professor Kielpinski said.

The precision involved in this process is almost beyond imagining.

“If we change the frequency of the light we shine on the atom by just one part in a billion, the image can no longer be seen,” Professor Kielpinski said.

This work opens up some new possibilities too,

Research team member, Dr Erik Streed, said the implications of these findings are far reaching.

“Such experiments help confirm our understanding of atomic physics and may be useful for quantum computing,” Dr Streed said.

There are also potential follow-on benefits for biomicroscopy.

“Because we are able to predict how dark a single atom should be, as in how much light it should absorb in forming a shadow, we can measure if the microscope is achieving the maximum contrast allowed by physics.”

“This is important if you want to look at very small and fragile biological samples such as DNA strands where exposure to too much UV light or x-rays will harm the material.

“We can now predict how much light is needed to observe processes within cells, under optimum microscopy conditions, without crossing the threshold and destroying them.”

And this may get biologists thinking about things in a different way.

Super resolution optical microscope built by Polish student

It’s been a while since I’ve had a microscopy story here and this Jan. 2, 2012 news item on Nanowerk gives me an opportunity to revisit the subject,

Optical microscopes are still second to none when it comes to analyzing biological samples. However, their low resolution, improved only in recent years in STED (Stimulated Emission Depletion) microscopes, continues to be a problem. …

Due to diffraction limit, optical microscopes will never be able to discern details smaller than 200 nanometres –[or so] it was believed only a dozen or so years ago. In recent years, scientists have managed to overcome this limit and build super-resolution devices, including, for example, STED confocal microscopes. A prototype device of this type has recently been built at the Faculty of Physics, University of Warsaw (FUW), as part of Joanna Oracz’s MA thesis. As of next year, the new microscope will be used not only for research in the field of optics but also to analyze biological samples.

I’ve been quite fascinated by the fact that the microscopes used in nanoscale research are haptic (touch) rather than optical. From the news item,

There are many imaging techniques with a resolution of the order of nanometres (billionths of a metre) known to science, for example, electron or atomic force microscopy [emphasis mine – this microscopy is haptic]. These techniques require special preparation of samples and make it possible to observe only the surface itself. When it comes to samples of biological origin, not infrequently living ones, optical microscopy is still second to none. One of its advantages is the possibility of observing the spatial structure of the sample. A major disadvantage, however, is a low resolution.

An optical microscope makes it possible to discern details no smaller than half the wavelength of the light illuminating the sample. This limit is due to diffraction, which makes it impossible to focus the beam of light onto a point. As a result, if we use a red light source with a wavelength of 635 nanometres, we can, at best, see details around 300 nanometres in size.

Here are some details about the new microscope,

The prototype microscope at FUW has a resolution of about 100 nm, over two times higher than that of a standard confocal microscope. [Work is] still underway to increase the resolution. “The advantage of our microscope is the possibility of controlling all parameters and studying the physics of the optical phenomena occurring,” stresses Oracz, currently a PhD student at the Ultrafast Phenomena Lab of the Institute of Experimental Physics FUW. The aim is to reach a resolution of about 60 nm. It would make it possible to observe details as minute as dendritic spines of neurons.

There’s more detail about the microscope at Nanwerk.