New Way to Catch Cancer's Spread, Rapid 3-D Retinal Imaging, Terahertz Sensing for Homeland Security


Lyndsay Meyer
The Optical Society


WASHINGTON, April 12 – Researchers from around the world will present new breakthroughs in optics, photonics and their applications at the 2007 Conference on Lasers and Electro-Optics/Quantum Electronics Laser Science Conference (CLEO/QELS) from May 6-11 at the Baltimore Convention Center in Baltimore, Md. The meeting is co-sponsored by the Optical Society of America (OSA), the American Physical Society Division of Laser Science (APS-DLS) and the IEEE Lasers & Electro-Optics Society (IEEE/LEOS).


At CLEO/QELS, researchers gather to present many of the latest breakthroughs on the science and engineering of photons and light waves. The following represent some of the many technical highlights at the meeting.

In an advance that can potentially assist cancer diagnosis, a new optical technique provides high-resolution, three-dimensional images of blood vessels by taking advantage of the natural light-absorbing properties of hemoglobin, the red-blood-cell molecule that carries oxygen throughout the bloodstream. 

Developed at Duke University, the new laser-based method should provide 3-D images of blood vessels in relatively deep tissue (up to 1 mm) with a resolution at the micron scale (at the level of blood cells, which is better than MRI resolution). Since hemoglobin is highly concentrated in red blood cells, imaging the locations where this molecule occurs can map out the distribution of red blood cells and reveal the vessels themselves. 

Clinically, the imaging technique can potentially be used to detect the spread of cancer, since angiogenesis—the growth of new blood vessels from existing ones—often signals the proliferation of tumors. This may make the technique convenient and powerful for helping to diagnose diseases such as melanoma. Since the technique can image blood vessels up to a millimeter below the surface, looking at vessels just below skin growths would be very useful for distinguishing between malignant and benign skin tumors, and would remove the critical need for skin biopsies, which is especially helpful if there are multiple suspicious areas that need to be investigated.

While the technique has been demonstrated in vitro (by excising tissue samples and imaging the vessels on a glass dish), imaging in the living body is possible either for vessels up to a millimeter below the surface or through the use of minimally invasive probes, being developed in various labs, that can be inserted in the body. (Paper CTuF1, "Two-Photon Absorption Imaging of Hemoglobin")

Researchers in Italy have created the shortest light pulse yet—a single isolated burst of extreme-ultraviolet light that lasts for only 130 attoseconds (billionths of a billionth of a second). Shining this ultrashort light pulse on atoms and molecules can reveal new details of their inner workings—providing benefits to fundamental science as well as potential industrial applications. Working at Italy's National Laboratory for Ultrafast and Ultraintense Optical Science in Milan (as well as laboratories in Padua and Naples), the researchers believe that their current technique will allow them to create even shorter pulses well below 100 attoseconds. These isolated attosecond pulses promise to probe electron phenomena such as "wavepackets"—specially tailored electron waves inside atoms and molecules that may help scientists use lasers to change the course of chemical reactions for scientific and practical uses, such as controlling the breaking of bonds in complex molecules for medical and pharmaceutical applications. (Paper JThA5, "Isolated Attosecond Pulses in the Few-Cycle Regime")

Striving to help ophthalmologists improve diagnoses of many eye diseases, researchers will introduce a new type of laser for providing high-resolution 3-D images of the retina.  The 3-D retinal imaging is performed with an emerging method called optical coherence tomography (OCT), which uses light to obtain high-resolution images of the eye, even for structures such as the retina, which lie beneath the surface.   

Conventional OCT imaging typically yields a series of two-dimensional cross-sectional images of the retina, which can be combined to form a 3-D image of its volume. Even more helpful for diagnosing disease would be to obtain very-high-resolution three-dimensional views of the eye. Limited imaging speeds and involuntary eye motion (such as blinking) make it difficult to perform 3-D imaging of the retinal volume.

Robert Huber (now at the Ludwig Maximilians University in Germany) and colleagues at MIT have reported retinal scans at record speeds of up to 236,000 lines per second, a factor of 10 improvement over current OCT technology. With their technique, which uses a frequency-tunable laser to achieve fast scan speeds, they obtained a 3-D retinal image consisting of 512x512x400 volume elements of data in a human subject in just 0.87 seconds. Future clinical studies, as well as further development, may someday enable ophthalmologists to routinely obtain high-resolution "OCT snapshots" of the retina's 3-D microstructure.  Such snapshots could potentially improve diagnoses of retinal diseases such as diabetic retinopathy, glaucoma, and age-related macular degeneration. (Paper CThAA5, "Fourier Domain Mode Locking (FDML) in the Non-Zero Dispersion Regime: A Laser for Ultrahigh-Speed Retinal OCT Imaging at 236kHz Line Rate")

An MIT-Sandia team will demonstrate the first real-time terahertz (THz) imaging system that obtains images from 25 meters away. Terahertz radiation, or far-infrared light, is potentially very useful for security applications, as it can penetrate clothing and other materials to provide images of concealed weapons, drugs, or other objects. However, THz scanners usually must be very close to the objects they are imaging, since water vapor in the air usually absorbs THz radiation very strongly.

In the MIT-Sandia design, a special device known as a "quantum cascade laser" delivers light in one of the few terahertz-frequency regions (specifically, around 4.9 THz) that water does not absorb in significant amounts. The researchers shine this light through a thin target with low water content (for example, a dried seed pod), and a detector on the other side of the sample records an image. 

Increasing the sensitivity of the detectors and the power of the laser (which currently must be chilled to low temperatures to radiate sufficiently high levels of THz waves) can potentially enable imaging of thicker objects or even imaging of the reflected THz light, which would be more practical for security applications. In the closer term, however, this approach may enable sensing of chemical residues or contaminants in the air. (Paper CThU3, "Real Time, Transmission-Mode Terahertz Imaging Over a 25-Meter Distance")

A Princeton group led by Evgenii Narimanov will discuss a newly emerging optical design known as a "far-field hyperlens." The hyperlens aims to increase light's abilities to image and magnify submicroscopic objects such as the components of biological cells. The lens is built with metamaterials, composite objects usually made from nanometer-scale arrays of rods and ring-shaped structures. It can project an image relatively far away (therefore making it "far-field"). The cylindrical shape of the hyperlens can collect components of the light waves that in a conventional lens would be lost. This helps the hyperlens capture details smaller than the wavelength of the illuminating light. In addition to such "subwavelength imaging," the hyperlens' cylindrical geometry enables it to magnify an object's image.

The Princeton group theoretically proposed the hyperlens (Jacob, Alekseyev, Narimanov, Optics Express, Vol. 14, Issue 18, pp. 8247-8256, September 2006), and six months later it was demonstrated experimentally (see, for example, Science, 315, 1686, 23 March 2007). Nader Engheta's lab at the University of Pennsylvania has also proposed a device, called a "metamaterial crystal lens," essentially equivalent to the hyperlens (Physical Review B 74, 075103, 2006).  According to Princeton researcher Zubin Jacob, the initial prospects for the hyperlens are very promising, for applications ranging from imaging biological objects to making nanometer-scale circuit patterns. (Paper QTuD3, "Optical 'Hyperlens': Far-field Imaging beyond the Diffraction Limit")

The University of Maryland's Igor Smolyaninov will describe what his group calls a "magnifying superlens." Initially inspired by John Pendry's "perfect lens" idea, and drawing upon the Princeton hyperlens and U-Penn crystal lens concepts as well as Maryland's previous work, the magnifying superlens uses alternating layers of negative- and positive-index-of-refraction metamaterials. In negative-refraction metamaterials, light or other electromagnetic radiation bends in the opposite direction than it would in ordinary matter, making it potentially very useful for focusing images. The new device succeeds in magnifying the object while resolving details as tiny as 70 nanometers, much smaller than the wavelength of visible light. (Paper JMA4, "Magnifying Superlens in the Visible Frequency Range"; also see Smolyaninov et al., Science, 315, 1699-1701, 23 March 2007).

In efforts that can improve studies of biological objects and the construction of nanotech materials, a Berkeley group has invented "optoelectronic tweezers," a new way of controlling nanometer-scale objects. Optoelectronic tweezers, which use optical energy to create powerful electric forces in carefully prescribed places, differ from ordinary "optical tweezers," which use optical energy to create mechanical forces that can push things around. According to Berkeley's Aaron Ohta, the optoelectronic approach uses much less power than optical tweezers and the light doesn't need to be as carefully focused, helping to make the technique potentially easier for laboratories to implement.

In recent months the Berkeley group has had some success in using their locally controlled electric fields to manipulate the positions of tiny nanorods, or nanowires (100 nm in diameter and 1-50 microns long). Ohta says that the optoelectronic device will possibly be used to place nanorods for the sake of building 3-D circuitry or for positioning oblong-shaped cells or cell protrusions with micron-level precision. (Paper CThGG5, "Trapping and Transport of Silicon Nanowires Using Lateral-Field Optoelectronic Tweezers")

Sir John Pendry, a condensed matter theorist from Imperial College London's Blackett Lab, will present "Metamaterials and Negative Refraction." He will give a brief history of negative refraction – a phenomenon that causes light to bend in an unusual way – from its theoretical conception in the 1960s to its eventual experimental verification this past decade. He will discuss applications of negative refraction, such as efforts to create a "perfect lens" and cloaking devices, as well as progress on negative refraction at optical frequencies.

Alan Heeger of the University of California at Santa Barbara and recipient of the 2000 Nobel Prize in Chemistry will present "Plastic Electronics and Opto-Electronics." Plastics ordinarily do not conduct electricity, but advances in chemistry can transform the cheap, flexible, and easy-to-manufacture materials into conductors or semiconductors for useful electronics and optics applications. For example, Heeger will discuss plastic solar cells fabricated from semiconducting polymers.

William D. Phillips of the National Institute of Standards and Technology and recipient of the 1997 Nobel Prize in Physics will present "Spinning Atoms with Light." He will describe how laser beams can transfer a property known as orbital angular momentum to groups of atoms. This achievement opens up new possibilities for data storage and computing.

The keynote for the CLEO/QELS collocated conference, Photonics Applications, Systems and Technologies (PhAST), John Ambroseo, president and CEO of Coherent, Inc., will present "The Photonics Industry: Enabling Technology or Mature Market?" He will give a brief history of the laser, which in its 50 years has helped create the backbone of the Internet, enabled the rapid improvements in computers described by Moore's Law, restored eyesight, and made possible cosmetic laser procedures. He will discuss how the photonics industry can evolve to ultimately become a true growth industry.

A Press Room will be located in the Pratt Street East room of the Baltimore Convention Center. The Press Room will be open Sunday, May 6 from 12 p.m. – 4 p.m. EDT and Monday, May 7 – Thursday, May 10 from 7:30 a.m. – 6 p.m. EDT. Those interested in obtaining a meeting badge for the Press Room should register online at or contact OSA's Lyndsay Meyer at 202.416.1435,

A press luncheon panel will take place on Tuesday, May 8 at 12 p.m. in the Baltimore Convention Center. The press luncheon will offer an overarching perspective on significant new developments to be unveiled during CLEO/QELS. The panel will also introduce some of the most promising applications for optical technology. To register for the press luncheon contact OSA's Lyndsay Meyer at, 202.416.1435.


With a distinguished history as one of the industry's leading events on laser science, the Conference on Lasers and Electro-Optics and the Quantum Electronics and Laser Science Conference (CLEO/QELS) is where laser technology was first introduced.  CLEO/QELS combines the strength of peer-reviewed scientific programming with an applications-focused exhibition to showcase the present and future of this technology.  Sponsored by the American Physical Society's (APS) Laser Science Division, the Institute of Electronic Engineers/Laser and Electro-Optics Society (IEEE/LEOS) and the Optical Society of America (OSA), CLEO/QELS provides an educational forum, complete with a dynamic Plenary, short courses, tutorials, workshops and more, on topics as diverse as its attendee base whose broad spectrum of interests range from biomedicine to defense to optical communications and beyond.  For more information, visit the conference's Web site at  




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