A Superlens For Nanoscale Optical Imaging | Superlens Nanoscale Optical Imaging

By Roland Piquepaille

Using a thin film of silver as the lens and ultraviolet (UV) light, scientists at UC Berkeley have built a superlens able to record images with a resolution of 60 nanometers and suitable for integration in today's optical microscopes which have only a resolution of down to 400 nanometers. Scanning electron and atomic force microscopes can capture detail down to a few nanometers, but they need minutes to take an image, while this new superlens can take snapshots in a fraction of a second. In the short term, this superlens will lead to new nanoscale biomedical imaging devices. But it also can lead to other advances in nanoengineering such as higher density electronic circuitry or faster fiber optic communications systems. Read more...

Let's start with a brief description of this achievement.

Using a thin film of silver as the lens and ultraviolet (UV) light, the researchers recorded the images of an array of nanowires and the word "NANO" onto an organic polymer at a resolution of about 60 nanometers. In comparison, current optical microscopes can only make out details down to one-tenth the diameter of a red blood cell, or about 400 nanometers.

At top (A) is the higher resolution image of the word NANO created with a silver superlens. Below that (B) is an image created during a control experiment in which the superlens is replaced by spacer layer. The averaged line width is 60 nanometers in image A with the superlens, and 321 nanometer in image B without the superlens. The scale bar in both images is 2 micrometers. (Image by Cheng Sun, UC Berkeley; legend from UC Berkeley).

Here is a link to a larger version (1,500 x 836 pixels, 214 KB).

[And here are the] detailed procedures of obtaining averaged line cross-section profiles (Color Scale 0-50nm): (A) AFM topography of NANO pattern of the recorded image; (B) Zoom-in AFM image of the letter "A"; (C) A further zoomed-in scan for sufficient digitization of individual lines (in this case each pixel measures 3.9nm) (Credit: UC Berkeley).

Here is what one of the scientists says about this superlens.

"The field of optics is involved in much of today's technology, including imaging and photolithography, which is used to make semiconductors and integrated circuits," said Xiang Zhang, UC Berkeley associate professor of mechanical engineering and principal investigator of the study. "Our work has a far reaching impact on the development of detailed biomedical imaging, higher density electronic circuitry and ever-faster fiber optic communications."

The biggest advantage of optical microscopes equipped with this new superlens over scanning electron and atomic force microscopes is the speed at which it can take images.

"Optical microscopes can capture an entire frame with a single snapshot in a fraction of a second," said Nicholas Fang, [one of Zhang's former Ph.D. students,] who is now an assistant professor of mechanical engineering at the University of Illinois at Urbana-Champaign.

"That opens up nanoscale imaging to living materials, which can help biologists better understand cell structure and function in real time, and ultimately help in the development of new drugs to treat human diseases."

Besides using this superlens for optical imaging or high-density optoelectronics, these researchers have also long term visions -- or dreams.

In the long run, this line of research could lead to even higher resolution imaging for distant objects, the researchers said. This includes more detailed views of other planets as well as of human movement through surveillance satellites.

Now, let's go down to Earth.

The research work has been published by Science Magazine on April 22, 2005 under the title "Sub-Diffraction-Limited Optical Imaging with a Silver Superlens" (Vol. 308, Issue 5721, Pages 534-537). Here is a link (free registration required) to the abstract which is reproduced below for your convenience.