Laser Innovation: Why the Next 50 Years Look Even Brighter
There can be no question that in the 50 years since its invention, the laser has driven scientific and technological innovation into virtually every facet of modern life. From surgery to communications, from medical diagnostics to printing, from metal-cutting to retail management, the laser has proven an essential and transformational tool.
But will the laser continue to drive similar advances in the future? Or will it level off into a useful, but increasingly mundane technology supporting incremental progress?
The answer: The laser shows every sign of continuing its uniquely creative role. If anything, that role is expanding. "The laser is so special because it allows us to harness light in a unique way," says Nicholas Bigelow, Lee A. DuBridge Professor of Physics and professor of optics at the University of Rochester. "Light is the 'quanta' of electromagnetism, which means that light is the carrier of the fundamental force that shapes the world as we know it."
Such centrality enables the laser to have an exceptionally broad and practical impact on numerous levels and in multiple areas. In terms of sheer quantity of patents issued to 20th Century inventions, the laser ranks third (see chart below).
"Even fifty years after the invention of the laser, new applications are being patented at a phenomenal rate," says Professor Tom Baer, executive director of the Stanford Photonics Research Center. "The total number of laser patents issued since its invention is well over 50,000, placing it in good company with other innovations such as the computer, the LCD, and fiber optics."
The Beginning: A Device in Search of Employment
The power of controlled light energy was not obvious to scientists even after Theodore Maiman invented the first working laser in 1960 - 50 years ago as of May 2010. A flash-lamp in Maiman's early device delivered photons to a ruby crystal, exciting electrons in the crystal's chromium atoms to a higher energy level. As the electrons began returning to their original energy level, they stimulated other excited chromium atoms to release their energy, all at the same deep red wavelength. Mirrors at the ends of the ruby rod formed the cascade of photons into a bright beam of red light, which lasted as long as the flashlamp pulse.
But for what purpose? Few immediate applications were apparent. Gradually, however, uses emerged. The military employed lasers to mark targets in Vietnam for smart bombs. Laser alignment helped contractors build sewers and rapid transit systems in the San Francisco Bay Area. The laser scanner read retail bar codes. Ophthalmologists used lasers to weld detached retinas back into place. By the late 1980s, the handheld laser pointer, one of the most ubiquitous consumer applications of laser light became practical. Yet, for all its advances, laser technology still performed a bit raggedly. Twenty years ago, for example, many scientists spent more time maintaining and repairing their laboratory's argon ion and dye lasers than they did conducting actual experiments.
Ongoing Enhancement + Radical New Designs
Today, development of basic lasers has stabilized. Hundreds of millions operate reliably in thousands of applications. Individual semiconductor lasers, looking like little pieces of metallic confetti, appear in everything from laser pointers to CD players. Refrigerator-sized carbon dioxide lasers cut metal, while their smaller, wine-cooler-sized cousins mark identification codes and expiration dates on consumer products. Still, innovation to the basic laser continues. Some enhancements gradually expand the laser's capabilities by, for example, increasing the number of laser wavelengths. X-ray lasers at short wavelengths of a few Angstroms promise to allow biochemists to observe chemical reactions in a single molecule as they occur. On the other end of the spectrum, lasers emitting millimeter waves at terahertz frequencies promise to help airport personnel perform safe, yet thorough passenger body scans for hidden weapons. Other enhancements include modification of laser light pulse rates or, more recently, laser pulse shapes. These customized pulse shapes can interact with highly targeted molecules to trigger chemical reactions that might not otherwise occur.
Moreover, radically new laser systems do continue to emerge. Take the quantum cascade laser, which, unlike the conventional semiconductor laser and its two-material approach to photon creation, employs multiple layers of different materials to create a cascade of photon-generating electrons. After just 15 years since its first laboratory demonstration (a very short time span for science), the quantum cascade laser proved the star of the 2009 annual Conference on Lasers and Electro-Optics (CLEO). There it demonstrated, among many other capabilities, remote atmospheric sensing of gases. Other scientists are contemplating new lasers based on a single atom. As Wayne Knox, director of the Institute of Optics at the University of Rochester observes, "There has been such progress in creating whole new classes of lasers even in the last 10 years, that you can only imagine it increasing."
Burgeoning Applications + Future Potential
Yet even if development of new laser types were to somehow stop, opportunities for new applications using existing laser technology would continue to expand. The laser's capability, now multiplied by a near infinite combination of available wavelengths, pulse durations, pulse shapes and power levels, has exponentially increased its range of potential applications. Add other tools like new software and the laser becomes an allpurpose innovation kit.
To some scientists, in fact, finding new uses for existing laser technology seems likely to provide the most dramatic breakthroughs. As Dr. Warren Warren, professor of chemistry at Duke University and chair of the Division of Laser Science of the American Physical Society, puts it: "The excitement is going to be less in developing new kinds of lasers than in figuring out great applications for lasers."
What new capabilities could emerge over the next five to 10 years? Keeping in mind that science rarely proceeds in a straight line, here's a sampling of possibilities:
Farreaching medical diagnosis
- Improved cancer diagnosis via lasers that illuminate cellular activity. One approach uses shaped laser pulses to penetrate into moles deep enough to detect melanomas. Another uses laser holography to examine deeper levels of ovarian tissue where cancer often first appears.
- Early diagnosis of Alzheimer's Disease by measuring beta amyloid, the disease's signature protein, with a pulsed, blue light laser aimed at the eye—the location in the body where beta amyloid typically shows up years before other Alzheimer's symptoms. The laser excites fluorescent dyes, added as a drop to the eye, which preferentially bind to the beta amyloid. Dr. Lee Goldstein, associate professor at Boston University's School of Medicine, College of Engineering and Photonics Center, who developed the technique, says: "Early detection of Alzheimer's Disease is the central problem in the field. If we're able to achieve it, we'll really have a much better possibility of arriving at a cure."
Dramatically more efficient computers and communications
- Construction of artificial materials or "metamaterials" that negatively refract light to focus it onto areas smaller than its wavelength and well beyond what is now possible with conventional optics. Tighter focus could lead to more precise photolithography and narrower semiconductor line widths that could, in turn, mean far smaller electronic components than are now viable.
- Supplanting wires connecting individual chips in a transistor with lasers, radically reducing power requirements for cell phones and computers. "As we get displays with more pixels and more colors, then the data rates going to these displays go up," notes John Bowers, director of the Institute for Energy Efficiency and professor of electrical and computer engineering at the University of California at Santa Barbara. "It is far more efficient and far cheaper to transmit that all optically rather than electronically. A new optical USB protocol has just been demonstrated, which means that in just a year or two, we will have 10 Gbit/s bi-directional optical connections on our laptops, allowing much faster communication to displays, memory and the Internet."
- Increased storage capacity of computer disks by a factor of 20 via a technique called Heat-assisted Magnetic Recording. The technique uses various laser properties to create much smaller bits than previously thought possible. This level of storage would allow almost all of the commercial movies ever made to be stored on a hard disk in a personal computer.
Lasers Boost Energy Applications
Laser fusion is in its infancy right now, but as research develops, there is the potential for laser technology to become a significant economic contributor in alternative energy. Similarly, laser technology will play a large role in emissions and environmental monitoring.
- The Department of Energy's Lawrence Livermore National Laboratory is conducting tests at its National Ignition Facility to develop the world's largest laser system, which will open the door to laser fusion—providing a virtually inexhaustible carbon-free alternative energy source.
- Researchers are working to replace traditional combustion engines with laser-based ignition to increase fuel efficiency and reduce harmful emissions. Laser techniques, including spectroscopy, can take in readings of environmental impurities, helping to keep a handle on emissions, water pollutants and other concerns. As it becomes more widespread, such monitoring will enable stricter standards and earlier notification of environmental contaminants, allowing for quicker clean-up and less negative impact.
Security and Protection
- A technique called LIBS, or Laser-Induced Breakdown Spectroscopy, shows promise at solving perhaps the central problem of modern organizations: Identifying new substances as they enter the organization's purview. Grocery stores need to know if spinach carries e coli bacteria; hospitals need to know if newly delivered pharmaceuticals are what their label says they are; the military needs to know if suspicious objects pose a threat. Work by researchers at the Army Research Lab and other organizations has advanced a technology that shoots a laser at an unknown substance, ablates a microscopic piece of it, then, from the resulting laser plume, makes a real-time spectroscopic analysis. Early results show an ability to distinguish between such complex organic materials as mold and simulated anthrax. LIBS-based chemometric analysis has progressed to the point where it will be included on NASA's 2011 Mars probe.
Understanding the universe
- New experiments to determine whether fundamental Newtonian and Einsteinian physical constants are, in fact, constant, and not drifting as the universe ages. The experiments are only possible because of advances in the atomic clock, based on lasers, which measures physical constants to 17 digits of precision.
- Atomic-and-molecular-level strobe pictures of physical and chemical reactions as they occur—thus furthering understanding of nature's fundamental building blocks. The enabling strobe illumination will come from attosecond lasers with pulses that last only 10-18 second.
- Unraveling of key questions of chemical physics, all by guiding chemical reactions with shaped laser pulses. Says Warren: "We'll better understand how one chemical bond breaks instead of another and how energy flows in molecules."
Each of the projected advances above, important as they are in isolation, will likely turn out to have far greater ramifications collectively. That is because the fundamental nature of light usually leads laser technology to morph across boundaries into unexpected disciplines. Advances in LIBS, for example, have led to projects in fields as diverse as paleontology (What substances are in a 110-million-year-old bird feather?), art (Is that painting a forgery?), and defense (What kind of metal is that and is it dangerous?).
Or take the example of laser diodes, developed with massive amounts of capital and manpower to make optical communications via the Internet cheap, reliable, and ubiquitous. Now optical engineers are redirecting laser diode technology to manufacturing. High-powered fiber lasers cut the most difficult substances—eight-inch solid rock, precision metal aircraft parts, even explosives (which don't blow up because short-pulsed lasers emit little heat). Says Knox, "The telecom revolution, almost coincidentally, also created a manufacturing revolution."
The list goes on, but today in 2010, celebrating the 50th anniversary of the first working laser... Can there be any doubt that the laser and its applications will continue to proliferate?