Have you ever wondered why, or rather how, flowers have such bright colors? As you might imagine, some fairly complex physics and chemistry lie behind the vibrant reds, yellows, blues and greens that shine when sunlight meets leaf or flower.

Sunlight includes all the rainbow colors of the visible light spectrum, plus some invisible ones such as ultraviolet and infrared. Desert lavender, for instance, is blue because pigments in its flowers absorb yellow light and reflect other colors, which appear blue in combination.

But what, exactly, happens in that minuscule fraction of a second after a photon of sunlight strikes an atom in a plant pigment? In fact, what happens when a photon of light hits any atom in any substance, including the human body?

Marek Romanowski, associate professor in the biomedical engineering department, believes that understanding the behavior of light during this femtosecond moment will, among other things, improve the early detection and treatment of disease, particularly cancer.

Light Fantastic

Romanowski, who is also a BIO5 member, heads a UA research team that recently won a National Science Foundation award of $506,800 to help fund a multiuser femtosecond laser facility. The UA is providing a further $217,200. The system is described as "broadly tunable," meaning it is capable of producing any wavelength, or color, in the visible and near infrared spectrum. It is expected to lead to new research directions in photochemistry, spectroscopy, and imaging.

A femtosecond is one quadrillionth, or one millionth of one billionth of a second. When used in medical imaging, such short laser pulses can be used to produce clearer images and more accurate diagnoses of disease with no tissue damage and no background interference.

Understanding light behavior at the molecular level is important, said Romanowski, because this behavior is highly dependent on the environment of the molecules. "How the light is absorbed by the molecule essentially tells us whether the molecule is functioning properly or not," said Romanowski. "That could be extrapolated to the overall state of a cell, or to monitoring a disease within a cell."

Other research being conducted by Romanowski hinges on discovering how individual molecules respond to short pulses of light. When these responses are known, it will be possible to design new light-activated molecules, or molecular devices such as nanoparticles, that can be placed within cells to combat disease. "We will literally be able to fight disease at the flick of a switch," Romanowski said.

Multidisciplinary Impact

An important aspect of the high-energy laser is that researchers in many disciplines will use it in their research. A group of colleges and centers submitted the NSF proposal jointly, and this project exemplifies UA's reputation as an interdisciplinary research environment because it combines expertise from the College of Engineering, the BIO5 Institute, the Arizona Cancer Center, and the College of Science.

Romanowski explained that many different processes are initiated by the absorption of photons, and what happens in the ensuing femtoseconds is of interest to researchers in a wide range of disciplines. "Our ability to start that initial process may help us improve photovoltaic generation of electricity, or cancer imaging, or anything between, such as better optical materials."

The proposed configuration of the project can be visualized as a central high-energy laser hub that pumps out femtosecond pulses of laser light to a number of satellite laser receptors controlled by the various researchers on the project. They can then use those femtosecond laser pulses however they wish in their specific research.

For example, one team might be conducting solar energy research by using the laser pulses to investigate the efficiency of solar cells in the visible range of spectrum. Another team could be researching how to use laser light as a medical diagnostic tool using near-infrared light, and still others might be doing research related to optical sciences or materials sciences and engineering.

"This is a very effective way of maximizing resources because we buy one source and we provide space for individual researchers," Romanowski said. "It would be impossible for a single researcher to acquire a system like this from an individual grant. Instead, an individual researcher can acquire a detection set-up that is specific to his application, whatever it might be."

Leading Lights

Involved in the multifaceted project so far are professor and BIO5 member Scott Saavedra of the department of chemistry and biochemistry, whose research includes biological spectroscopy and solar energy conversion; associate professor and BIO5 member Urs Utzinger of the biomedical engineering department, who is interested in cancer tissue imaging; associate professor and BIO5 member Marty Pagel of the biomedical engineering department, who is developing medical contrast agents; and assistant professor Russ Witte of the radiology department, whose research involves photoacoustic imaging, which Romanowski described as "another modality of imaging that uses light to initiate an acoustic response from tissue."

Also taking part are Linda Powers, BIO5 member and professor in the electrical and computer engineering department, whose research includes microbe detection; and professor Ron Lynch of the physiology department, also a BIO5 member. Lynch, who is director of the Advanced Research Institute for Biomedical Imaging, uses advanced imaging techniques in his diabetes research.

Sadly, one of the new laser facility's great champions, Arizona Research Labs director Michael Cusanovich, did not see this project come to fruition. Cusanovich died in April 2010. "He was a member of the team," Romanowski said. "His ARL provided partial funding, and his support for the idea was unmatched. I was looking forward to this opportunity to collaborate with Mike, and I want to acknowledge his part in this."

Getting back to the barely understood light processes that occur in nature, Romanowski reflected on how little we actually know. "We have those examples in nature that put us to shame. Photosynthesis does things that we still cannot do with the same efficiency."

"With this new broadly tunable femtosecond laser, we're trying to gain a better understanding of the physical and chemical processes initiated by light absorption," he said. "With only a dozen or so similar installations in the US, multiuser laser facilities are rare, and this is one of them."