Quantum lasers reveal unprecedented nanoscopic details

Posted by Rick C. Hodgin

Cambridge (MA) - Harvard scientists have developed a "quantum cascade (QC) laser nanoantenna" which is capable of scanning the interior of a cell with unprecedented detail.  While not limited merely to biology, this new device is revealing the world of the ultra-small in big ways.

As illustrated here, the laser operates from a cascade emitter array placed between two nanoscopic gold rods, which serve as an "optical antenna".  The rods are used to direct the laser toward a nanoscopic dot of focus.  The focus dot is about 50x to 100x smaller than the wavelength of the laser light itself, which is programmatically tuned to that part of the invisible spectrum where cells have something called an "absortion footprint".  The laser is focused as scans are taken back and forth in a 3D volume of space.  As the data is read back to the device, a computer assembles it.  The end result is an extremely fine grained scanning device which yields unheard of nanoscale details.

To visualize exactly what it's doing, consider normal nanoscopic scanning techniques to be like looking through a big block of ice.  Due to the small size, whatever's inside would appear to be distorted and hard to make out to the naked eye, or in this case the traditional nanoscopic devices.  What the new technology does is provide a way to see through the distortions and get a very accurate view of what's on the inside.  It does this by taking extremely tiny data points, and then assembling them into a more realistic 3D representation of the actual cell.  When combined with other scanning techniques which could take images of the surface, or provide volumetric information of the cell's physical size, the data comes together to produce an extremely accurate model of whatever's being scanned.

Dr. Federico Capasso had this to say on the technology, "By combining Quantum Cascade Lasers with optical antenna nanotechnology we have created for the first time an extremely compact device that will enable the realization of new ultrahigh spatial resolution microscopes for chemical imaging on a nanometric scale of a wide range of materials and biological specimens".  Basically, what Capasso is so elegantly stating is that we now have the technology to look at the uber-small using relatively inexpensive techniques, and ones which provide accuracy which will undoubtedly yield significant advances in the areas of medicine and biological research.  The technique can also be applied to chemicals and other miniscule substances.  It is not limited to only living material either, though that was the focus of the paper.

This project was directed by Nanfang Yu, Ertugrul Cubukcu, and Federico Capasso.  Robert L. Wallace, a professor of applied physics, and all of Harvard's School of Engineering and Applied Sciences, also worked together on the research.  The findings were published in an October 22 issue of Applied Physics Letters.  The reserach team is also looking to patent their technology as "a new class of photonic devices".