7
Optics Research and Education

Research in optics has a long and distinguished history, dating back even further than the work of Galileo and Newton. In recent decades, optics research has blossomed with the invention of the laser, an increasing interaction between optics and electronics, the development of new materials with unique optical properties, and other extraordinary advances. The first part of this chapter highlights some examples of research areas that hold special promise for further discoveries. This is a time of great excitement for all optics researchers, whether in universities, industry, or government laboratories.

The second part of the chapter discusses the state of optics education. Combining this report's discussion of research and education issues in a single chapter is only appropriate. The creation of research universities, which combine research and education endeavors to create a synergy between the discovery of knowledge and the education of students, has been one of the key institutional developments of the past century for research and education in optics as in other fields.

Introduction

Both basic and applied research are motivated by a deeply rooted human instinct: the desire to know and understand nature. Over hundreds of years, humans have gradually learned to explore nature in a systematic way known as the scientific method—the use of experiments and observations, guided initially by intuition and hypothesis and later by theory. The resulting understanding of nature is the hallmark of the scientific process. Roger Bacon, a multitalented thirteenth-century scientist and philosopher whose work in optics included a description of a telescope



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Harnessing Light: Optical Science and Engineering for the 21st Century 7 Optics Research and Education Research in optics has a long and distinguished history, dating back even further than the work of Galileo and Newton. In recent decades, optics research has blossomed with the invention of the laser, an increasing interaction between optics and electronics, the development of new materials with unique optical properties, and other extraordinary advances. The first part of this chapter highlights some examples of research areas that hold special promise for further discoveries. This is a time of great excitement for all optics researchers, whether in universities, industry, or government laboratories. The second part of the chapter discusses the state of optics education. Combining this report's discussion of research and education issues in a single chapter is only appropriate. The creation of research universities, which combine research and education endeavors to create a synergy between the discovery of knowledge and the education of students, has been one of the key institutional developments of the past century for research and education in optics as in other fields. Introduction Both basic and applied research are motivated by a deeply rooted human instinct: the desire to know and understand nature. Over hundreds of years, humans have gradually learned to explore nature in a systematic way known as the scientific method—the use of experiments and observations, guided initially by intuition and hypothesis and later by theory. The resulting understanding of nature is the hallmark of the scientific process. Roger Bacon, a multitalented thirteenth-century scientist and philosopher whose work in optics included a description of a telescope

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Harnessing Light: Optical Science and Engineering for the 21st Century (more than 300 years before anyone actually built one) and the first application of geometry to the study of lenses and mirrors, is often considered the forerunner of experimental science and the scientific method. Applied research, which is often indistinguishable from basic research, is motivated by the need to understand how as well as the need to understand why. Louis Victor de Broglie, recipient of the 1929 Nobel Prize in physics, explained that ''the two aspects of science [pure and applied] correspond to the two principal activities of man: thought and action. They are inseparable if human science is to progress as a whole and fulfill with increasing success its high and twofold task." Decades of basic and applied research are often needed to lay the foundations for key discoveries, such as the invention of the laser. The most important discoveries often arise at boundaries between established fields—in the case of the laser, at the interface between physics and electrical engineering. The ultimate impact of research is rarely predictable. For example, as the earlier chapters of this report demonstrate repeatedly, the invention of the laser has had a major economic and social impact, with remarkable applications in areas that range from communications to the environment to medicine. Yet Arthur Schawlow, the laser's coinventor, once commented that "if I had set out to invent a way to improve eye surgery, I certainly would not have invented the laser." Development, often guided by understanding gained through basic and applied research, is motivated by a need to make something that works and is of commercial value. However, development—especially the development of commercial products—usually requires a much larger financial investment than most research. Such resources are often unavailable at universities; therefore, in the United States, development activities are generally concentrated in the commercial sector. The exception is in certain areas of special interest to the nation, such as defense, space, and the environment. Military needs in particular have historically motivated substantial support for long-term optics R&D by the Department of Defense—support that has been very important over the years but that is being reduced, leading to concern about a gap emerging between basic conceptual research and commercial hardware development. Development often involves multiple scientific and engineering disciplines, multiple approaches to problem solving, and the unique techniques and resources of large public and private organizations. Education at all levels is critical to the future of optics. Optics is a natural tool for a visual approach to the education of K-12 students in many aspects of science and mathematics. Post-high school education, including 2-year (associate) and 4-year degree programs, is important for meeting the future needs of this rapidly growing area of

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Harnessing Light: Optical Science and Engineering for the 21st Century knowledge. There is a need for graduate education, as discussed below, as well as special courses of study in optical engineering provided by universities with an historical focus on optics. Jobs are available for those trained in optics. It is often asked whether optics constitutes a separate discipline, and this question requires critical attention. Optics is certainly recognized as an integrated field of knowledge. Its teaching extends across disciplinary boundaries and includes science departments, engineering departments, and departments in schools of medicine. Because the field of optics is not sharply defined by a job title or membership in a single professional society, it can be difficult to develop a quantitative picture of the size and breadth of the optics research community. One indicator is participation in professional conferences. About 6,000 scientists and engineers usually attend the annual U.S. Conference on Lasers and Electrooptics (CLEO). The Optical Fiber Conference attracts more than 7,000 participants each year. Other major conferences in optics include the annual meeting of the Quantum Electronics and Lasers Society, the International Quantum Electronics Conference, the annual meeting of the Optical Society of America, the Lasers and Electrooptics Society annual meeting, and conferences organized throughout the year by SPIE, such as Photonics West and Photonics East. Altogether, the field involves at least 30,000 active scientists and engineers worldwide, and many areas of the optics industry are growing rapidly. Another indicator of the strength and growth of the field is its impact on the economy. Optoelectronics is now a major component of U.S. import and export trade. The rate of formation of optics-related businesses has grown rapidly during the 1990s. The need for greater investment in research and education in optics was recognized in a 1994 National Research Council (NRC) study, Atomic, Molecular, and Optical Science (the FAMOS study). Although this study focused on a narrow segment of the field of optical science and did not address the engineering aspects, it nevertheless found that this field is ripe for breakthroughs, growing rapidly, and having an impact on sciences beyond optics, including biology, chemistry, and medicine. Today, the United States invests approximately 0.5% of its gross domestic product (GDP) on research in its research universities. This is the lowest rate of such investment by any major industrialized country. As a result of a workshop in May 1994,1 the National Science Foundation (NSF) in 1995 announced a multidisciplinary research initiative in optical science and engineering. The program attracted more than 600 pre-proposals and 70 full proposals. Ultimately only 1 The workshop produced a report; see NSF (1994).

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Harnessing Light: Optical Science and Engineering for the 21st Century 18 projects could be funded. These numbers indicate both the vitality and the competitive nature of optics research and the strong interest nationwide in the opportunities it presents. In recent years an important feature of optics research has been the growing interaction between optical physics and electrical engineering. The first hint of this link was the discovery by Heinrich Hertz in 1883 that radio waves and light waves are described by the same theory of electromagnetism and are distinguished only by their different frequencies. Marconi soon demonstrated the transmission of information by pulsed radio waves, and by the 1920s there were more than 30 million radios in use in the United States alone. From the development of electrical devices for radio and other applications came a new research discipline, electrical engineering. In this same period, physicists were exploring newly discovered properties of light. Max Planck found that light is quantized in units called photons. Einstein used this discovery to explain the emission and absorption of light quanta by atoms and predicted that it should be possible to use light to stimulate an atom to emit more light. Other physicists—most of them engaged in basic research with little thought about potential applications—explored electrical discharges, the properties of atoms in solids, the properties of semiconductors, and atomic and molecular spectroscopy. The two communities—physicists, with their emphasis on quantum mechanics and the basic understanding of nature, and electrical engineers, with their understanding of electronic circuits and wave propagation—were brought together in 1960 by the invention and demonstration of the laser (named for light amplification by stimulated emission of radiation). Today, work at the interface of physics and electrical engineering is a key element of optics research, producing such important developments as the semiconductor diode laser. Optics is a multidisciplinary field that cuts across many of the traditional academic disciplines. The funding of initiatives in such crosscutting areas is often hindered by the structure and organization of the federal agencies that support research and development. In an effort to overcome these difficulties, the government has created the National Science and Technology Council (NSTC) and charged it with addressing the following goals: to maintain leadership across the frontiers of scientific knowledge; to enhance connections between fundamental research and national goals; to stimulate partnerships that promote investments in fundamental science and engineering and in the effective use of physical, human, and financial resources; to produce the finest scientists and engineers for the twenty-first century; and to raise the scientific and technology literacy of all Americans. These goals serve as guideposts for NSTC in making recommendations and setting priorities for investment in new crosscutting research and development

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Harnessing Light: Optical Science and Engineering for the 21st Century opportunities that involve multiagency and multidiscipline collaboration and support. NSTC works to identify important crosscutting science and technology programs and works with multiple agencies to fund new initiatives. For example, an initiative on high-performance computing and communications involves nine agencies and an investment of $1 billion (National Science Board, 1996). As demonstrated throughout this report, the broad area of optics is multidisciplinary and growing rapidly. It is ripe for support as a crosscutting initiative at a level comparable to the earlier investment made in high-performance computing and communications. Multiple government agencies should form a working group to collaborate in the support of optics, in a crosscutting initiative similar to the earlier one for high-performance computing and communications systems. NSF should develop an agency-wide, separately funded initiative to support multidisciplinary research and education in optics. The Department of Commerce should explicitly recognize optics as an integrated area of knowledge, technology, and industry and should structure its job and patent databases accordingly. Research Opportunities Opportunities for research in optics have the potential for significant benefit to society in the next decade. Many new developments, with a high leverage for return on the investment of increasingly scarce research dollars, have been identified. However, research by its nature returns benefits on a portfolio of many possible avenues of investigation. A few examples of the many areas of research in optics that show promise and offer high leverage for future return are presented in this section. It is impossible to cover all areas of research in the extensive and multidisciplinary areas of optics. A more inclusive set of research opportunities in optics is presented each year at large annual meetings such as CLEO. Areas of optics research selected for discussion include control of atoms by light, fundamental quantum limits of measurements, and light in biology. Recent advances in optical microscopy are highlighted. Femtosecond laser technology and its application to ultrafast physics, chemistry, and engineering is identified as a particularly promising opportunity. Advanced laser sources and frequency conversion of lasers using nonlinear optical devices offer significant potential for applications in semiconductor processing, reprographics, and image display. Semiconductor lasers and solid-state lasers are promising sources of coherent optical radiation at ever-decreasing cost. Advances

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Harnessing Light: Optical Science and Engineering for the 21st Century in optical materials are recognized to play an important role in the next generation of laser sources, nonlinear frequency converters, and new optical elements such as gradient index optics and media for optical storage of information. Finally, progress in the generation of coherent radiation progressed from radio frequencies in 1900 to microwave frequencies in 1930 and to optical frequencies in 1960. We are now entering the era of extreme ultraviolet (UV) and, in the future, coherent x-ray sources with applications that extend from lithography to advanced x-ray imaging. Quantum, Atomic, and Biological Optics Control of Atoms by Light Light continues to be the principal method of probing matter. Powerful spectroscopic techniques continue to be developed as light sources extend into new regimes of the electromagnetic spectrum and as optical sources with extremely short pulses such as femtosecond lasers, synchrotron sources, and free electron lasers become more widely used. In the past decade, light has begun to be used to detect and to control matter, particularly the position and velocity of atoms, molecules, and small particles. Currently, atoms in the gas phase can be laser-cooled to microkelvin temperatures where their velocities are on the order of a centimeter per second. Once cold, atoms can be manipulated with relative ease. Atoms tossed upwards in a ballistic trajectory as in a fountain form the basis of a new generation of atomic clocks. Prototype atomic fountain clocks already have short-term stability an order of magnitude better than atomic clocks based on thermal beams of atoms. Alternatively, ions trapped in magnetic and electric fields could lead to atomic clocks based on optical transitions in which the stability would be improved another thousandfold. (Since ion clocks will have a low signal-to-noise ratio, they will need stable "flywheel" frequency references, such as ultrastable hydrogen masers or cryogenic microwave oscillators, to take full advantage of this potential for superior accuracy.) Atom traps have also been used to store radioactive isotopes for nuclear physics studies and for tests of fundamental symmetries of nature such as parity and time. Atom optics has emerged as a new field. Atom lenses were used to deposit 0.05-µm lines and dots on a surface. These structures can be written over large areas and may be used to pattern a surface for high-density optical storage. One promising approach uses the optically guided atoms to react chemically with a resist with better than 0.1-µm spatial resolution. Atom beam splitters, mirrors, and diffraction gratings have been used to construct atom interferometers. Atom interferometers have already proven to be sensitive accelerometers and gyroscopes.

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Harnessing Light: Optical Science and Engineering for the 21st Century BOX 7.1 BOSE CONDENSATION In 1925, Einstein made a dramatic prediction. If the atomic density n increases to nλDeB3 = 2.612, where λDeB is the DeBroglie wavelength, a sizable fraction of the atoms will condense into a single quantum state. Examples of Bose condensation media include superfluid helium, paired electrons in a superconductor, and paired atoms in superfluid 3He. In 1995, 70 years after Einstein's prediction, research groups at the University of Colorado and the Massachusetts Institute of Technology achieved Bose condensation of a dilute gas of rubidium and sodium atoms by using a laser to cool the atoms. A year later, a group from Rice University was able to show that 7Li atoms also form a Bose condensate. Figure 7.1 shows the momentum distribution of a gas of (Rb or Na) atoms in the vicinity of the Bose condensation threshold. Just above the required phase space density (left), the atomic energy is distributed in all directions equally among the many occupied quantum states, in accord with the principles of statistical physics. As the threshold condition is crossed (center), a central peak at v = 0 begins to form, signifying the onset of a condensation. With further cooling (right), most of the atoms condense into the ground quantum state of the system. The properties of dilute Bose gases are being explored, and it is too early to predict how this field will develop. Perhaps new physics will be discovered. Perhaps Bose condensates will be used as intensely bright sources of atoms analogous to photons from a laser. The one certain prediction is that the future is hard to predict: The inventors of the laser had no idea of the myriad of ways in which their invention would contribute to science and technology. Freely falling atoms have been used to measure the acceleration of gravity with a precision of one part in a billion after 100 seconds of averaging time, and an atom interferometer gyroscope has exceeded the sensitivity of the best commercial laser gyroscopes. Atom gravity gradiometers currently being developed may eventually be used for oil exploration. The control of atoms permits the creation of new states of matter. For example, standing wave interference patterns caused by interfering laser beams create periodic potential wells in which atoms can be trapped. These so-called optical lattices offer a unique model system of "condensed matter" concepts in which the characteristics of either fermionic or bosonic particles can be probed. Atoms have been cooled with sufficient density that they have condensed into a single quantum state known as Bose-Einstein condensation (Box 7.1), predicted by Einstein (see Figure 7.1). Once the atoms are in a single quantum state, the concept of temperature is no longer valid. The properties of this new state of matter are now being studied with great fervor, and important applications will likely result from these studies. Photons, which share the same quantum statistical-mechanical properties as atomic bosons, have been made to "condense" into laser light. As the atom analogue to the

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Harnessing Light: Optical Science and Engineering for the 21st Century FIGURE 7.1 The momentum distribution of atoms during Bose condensation of a laser-cooled dilute gas. (Courtesy of M. Matthews, JILA.) laser, the Bose condensate may also revolutionize the way atoms are used just as the advent of the laser revolutionized the way light is used. Fundamental Quantum Limits of Measurement In addition to providing some of the most refined measurement tools, optics is and will continue to be the primary means of studying the fundamental limitations of any measurement. The measurement of a physical quantity is limited by the size of the signal relative to the noise in the measurement. Quantum mechanics defines the fundamental noise floor. For example, the uncertainty principle tells us that the simultaneous measurement of position and momentum with uncertainties Δx and Δp is limited to an accuracy ΔxΔp ≤ h, where h is Planck's constant. Similarly, the simultaneous measurement of the amplitude and phase of an electromagnetic wave is also limited. Although these fundamental limitations were known since the early days of quantum mechanics, we have only recently shown that the partition of quantum noise can be altered. For example, in a laser interferometer measurement of distance, the phase of the light in the interferometer is the quantity of interest. The phase noise due to the vacuum can now be "squeezed" into the amplitude sector, allowing more precise measurement of the phase of the interferometer. Before this refined measurement sees wide application, the methods of altering noise at the quantum limit have to be made easier. Quantum mechanics also tells us that any measurement of a physical system necessarily alters the system. This effect of the measurement on the system being studied can be tailored to influence different aspects of the system. To measure the intensity of a pulse of light, it is now possible to make a "nondemolition" measurement in which the number of

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Harnessing Light: Optical Science and Engineering for the 21st Century photons in the pulse is not altered; the unavoidable perturbation of the light pulse manifests itself with a change in the phase of the optical pulse. The quantum dynamics of strongly coupled quantum systems allows precise coherent control of both the internal state and the external dynamics of an atom. This type of quantum state engineering has already been pursued in order to control chemical dynamics. More recently, it was shown that it may be possible to engineer correlated quantum states where the sensitivity of an optical interferometer could be improved by the square root of the number of photons used in the measurement. Since the number of photons used in a measurement can be very large, the gain in sensitivity could be staggering. The study of highly correlated quantum states may also offer fundamentally new ways of transmitting information and computing. Unlike a classical computer based on irreversible, dissipative transitions between distinct states such as 0 and 1, a quantum computer based on the reversible quantum evolution of linear superpositions of quantum states could in principle greatly reduce the time needed to solve certain problems. For example, on a conventional computer the time required to determine a number's prime factors (a problem with important applications in cryptography) grows exponentially with the size of the number, so any computer can easily be overloaded. On the other hand, a factorization algorithm based on the logic of quantum computing necessitates only a polynomial growth in computing time. A practical quantum computer may never be realized because of the difficulty of maintaining the phase coherence of a system with many degrees of freedom, but this area of research will no doubt lead to greater facility in handling complex quantum systems and eventually to new technologies. The laser, the transistor, and magnetic resonance imaging are examples of how a deeper appreciation of quantum mechanics has led to technological revolutions. Optics will continue to provide some of the best tools for the exploration of quantum mechanics and quantum systems. Light in Biology Not only are optical techniques driving a revolution in the manipulation of atoms and the refinement of physical measurements, but they are also generating a resurgence in biological fields. Even the venerable optical microscope, invented in 1625 and "perfected" at the beginning of this century, is having a renaissance because of the confluence of several technological developments (see Figure 7.2). Fluorescence methods made possible with high-performance interference filters, laser illumination, and the synthesis of new dyes resistant to photobleaching have contributed to this resurgence. The fluorescence from single molecules can now be detected with detectors such as microchannel plate image intensifiers or avalanche photodiodes.

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Harnessing Light: Optical Science and Engineering for the 21st Century BOX 7.2 ADVANCES IN OPTICAL MICROSCOPY Technical innovations in the optical microscope have often been followed by major advances in biology. The invention of the first compound microscope in 1625 was followed quickly by the discovery of microscopic organisms such as yeast, algae, and protozoa. The construction of good-quality, high numerical aperture microscope objectives, the development of a method of achieving uniform sample illumination (Kohler illumination), and the introduction of cell-staining methods elevated microscopy to a general-purpose diagnostic tool in medicine. The introduction of phase contrast methods for observing unstained biological samples opened up the possibility of observing live cells. We are in the midst of a renaissance in the development of the microscope, generated by the integration of other technologies such as video cameras, image intensifiers with single-photon counting sensitivity, and computer pattern recognition and image deconvolution. Research into laser trapping techniques has led to "optical tweezers" that allow one to micromanipulate samples with light while simultaneously viewing them. The scanning confocal microscope, coupled to a computer, gives three-dimensional images of samples. Near-field optical microscopes have achieved molecular resolution. Molecular biology techniques now permit the staining of specific proteins expressed in living cells. What are the current technological challenges? Near-field optical techniques have to be improved so that molecular resolution can be routinely achieved for biological samples in water. Fluorescent tags with greater resistance to photobleaching and additional colored protein markers to complement the green protein marker will allow biologists to track protein-protein interactions in living cells. The most important ingredient is the invention of methodologies that will exploit these new tools. History has shown repeatedly that new discoveries in basic science have always followed significant technological advances. Proteins manufactured in cells can be tagged with a green fluorescent protein (GFP) by adding instructions to the protein DNA that result in a protein-GFP molecule. The fluorescent protein can then be seen as it moves in a live cell. The development of alternate color tags (such as red and blue dyes) will enable the observation of protein-protein interactions in a live cell in real-time. Two-photon excitation from inexpensive diode-pumped femtosecond lasers will permit the observation of the intrinsic fluorescence of biological molecules and molecules in the interior of tissues that could not otherwise be detected. Fluorescent dyes can also be used to monitor their local biological environment since the fluorescence is affected by conditions such as temperature, electric fields, and pH. New laser methods such as confocal microscopy for three-dimensional imaging and near-field optical microscopy with nanometer resolution are adding to the set of powerful, noninvasive optical diagnostic tools (Box 7.2). Lasers have also been used to control micron-sized

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Harnessing Light: Optical Science and Engineering for the 21st Century FIGURE 7.2 Four hundred years of progress in the history of the optical microscope. Rapid progress over the past 40 years is illustrated on the expanded scale. objects at room-temperature in aqueous solution. These so-called optical tweezers have given us the ability to manipulate individual cells, organelles within the cell, and even molecules in an optical microscope. For example, muscular contraction at the molecular level has been reduced to the interaction of a myosin molecule on an actin filament. Optical tweezers have been used to measure, in real-time, the force and displacement of the myosin molecule during hydrolysis of a single ATP (adenosine triphosphate) molecule. Just as powerful new insights have come from the study of single, isolated quantum systems, the study of biology at the level of a single molecular event will undoubtedly reveal unexpected behavior. The National Science Foundation should recognize the dramatic new opportunities in fundamental research in atomic, molecular, and quantum optics and should encourage support for research in these areas.

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Harnessing Light: Optical Science and Engineering for the 21st Century FIGURE 7.12 Diffractive-optic x-ray zone plate lens used to focus x-ray radiation. (Courtesy of E. Anderson, Lawrence Berkeley National Laboratory.) plate (see Figure 7.12) to focus the x rays. The short x-ray wavelength demands very high-precision in the fabrication of optical elements. Fortunately, metrologies are now available with accuracies measured in fractions of a nanometer, which permit fabrication of x-ray components with greatly reduced wavefront distortion. Considerable research remains to be done to fully develop high-quality x-ray optics suitable for lithography, microscopy, and other emerging applications. Multiple agencies with interest in the crosscutting science and technology of EUV and soft x-ray optics and techniques should encourage research in this area because of the substantial potential economic payback in the near future. Education in Optics Formal university-level education in optics started in the United States in 1927, after considerable national debate. The debate arose from the experience of World War I when "in all the allied countries, requirements of the armed forces had revealed woefully inadequate production facilities and an abysmal lack of trained engineers to design and build optical devices of every kind" (Kingslake and Kingslake, 1970). As a result, optics centers and institutes were founded in France, England, and eventually, the United States. The debate at the time was in some ways similar to discussions that continue today. Was there no tradition of optics in the United States before World War I? Indeed there was. Jackson's An Elementary Treatise on Optics was published in 1848 and was followed by a whole series of books, pamphlets, and handbooks. However, the debate, then as now, was about recognizing the existence of an integrated body of optics knowledge, that can and should be taught in a unified way. The recognition of optics as an integrated body of knowledge is the premise for this section's discussion of education. (This does not necessarily mean its recognition as a "discipline," however, or the creation of separate university departments. The field's diversity and multidisciplinarity are great strengths.) The broad picture for science and engineering education is reviewed periodically by the National Science Board and published in Science and Engineering Indicators (1996): The 500,000 degrees

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Harnessing Light: Optical Science and Engineering for the 21st Century earned in science and engineering in 1993 included 25,000 doctorates, 86,000 master's degrees, 366,000 bachelor's degrees, and 23,000 associate's degrees; in that year, 2.2 million people were employed in science and engineering jobs. Models of future employment demand are famously uncertain, of course, but only in the NSB's most aggressive growth scenario for the period 1994-2005, in which science and engineering employment expands by 62%, is there a strong demand for new scientists and engineers. The supply side has flexibility to respond to increased demand in a variety of ways, including the actions of individuals who have choices about education, retraining, postponed retirement, and moving to other technical fields. Small shifts in the career paths of employed scientists and engineers can have major effects on the supply and demand of scientists and engineers across fields. Yet because optics is a new field that is undergoing rapid growth, demand may not be met by such adjustments and additional students may be needed. This is already the case for many subfields of optics. In some subfields, the demand for trained employees already exceeds the supply. U.S. Optics Education Programs U.S. colleges and universities offer a wide variety of educational programs in optical science, technology, and engineering. Some of these programs have broad curricula that span the field of optics. Others have more limited curricula that are devoted to specific subfields. Over the years, there have been several attempts to compile directories of these programs. Two major guides are produced by the professional societies. The most recent is Optics Education 1996: Annual Guide to Optics Programs Worldwide, produced by the International Society for Optical Engineering (SPIE). The Optical Society of America (OSA) published a three-volume guide to optics courses and programs in 1992. Gathering such data is complicated, however, by the lack of a universally agreed-upon definition of the field. It should be noted that the major fields of engineering are recognized, in part, by the accreditation standards used by the Accreditation Board on Engineering and Technology (ABET) in evaluating university engineering departments. An accreditation program for optical engineering—similar to the ABET program for electrical engineering, for example—would provide several benefits, including an official government employment classification. This would help to identify prospective employees with specific experience and expertise; it would also help to provide a clear picture of the field's status by improving the basis for gathering statistics. The topic of accreditation was studied a few years ago by committees of OSA and SPIE. Their studies included discussions with ABET, but at the time, ABET concluded that there were too few formal programs to merit its attention and both

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Harnessing Light: Optical Science and Engineering for the 21st Century societies decided against seeking an accreditation program. Continued rapid growth in the field would be likely to change this conclusion. The 1996 Annual Guide lists some 114 U.S. institutions that offer programs in optics. Of these, 93 offer one or more degree programs at the bachelor's level or above. A majority (55%) of these 93 institutions offer all three degrees: B.S., M.S., and Ph.D. About 14% offer the B.S. and M.S. only, and about 25% the M.S. and Ph.D. only. A few offer only a single degree (this is not to say that a stand-alone bachelor's program cannot be successful; there are excellent examples to the contrary). It is important to note, however, that although the 1996 Annual Guide is quite useful, it is the result of self-reporting and should be evaluated carefully with this fact in mind. The professional societies should evaluate educational programs in optics and jointly produce an annual guide. Because of the strong correlation between education and scholarly publishing, the major optics research journals are useful indicators of optics education, especially when comparing the level of activity in different countries. For example, the 450 papers published in Optical Engineering in 1995 involved 1,333 authors, 64% of whom were associated with academic institutions. A total of 33 countries were represented, corresponding closely with the 31 countries known to have educational programs in optics; 155 of the 450 papers (and 432 of the 1,333 authors) were from the United States. Other optics journals (of which there are more than 50, less than one-third of them published in the United States) appear to present similar statistics. The high representation of academic institutions in these journals attests to the quality of academic scholarship, which is of course tied closely to the quality of educational programs, particularly at the graduate level (Thompson, 1996, 1997). Approaches to Academic Programs in Optics The term optics, as used this report, encompasses an extraordinarily wide range of study, including such subfields as imaging and image processing, photonics, electro-optics, acousto-optics, fiber optics, optoelectronics, and lasers. The fundamentals of geometrical optics, physical optics, and quantum optics are the foundations of many of the teaching programs in these areas. Major educational institutions here and abroad offer structured programs that cover fundamentals, applied topics, and engineering applications from components to systems. Thus, unlike traditional departmental disciplines, optics cuts across traditional educational boundaries, involving the full range from very basic academic science to applied science to technology to systems engineering. For example, Chapter 1 notes the importance of education in systems issues for employment in the communications, display, and information storage industries. Chapter 6 notes that students educated in optics manufacturing are in high demand.

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Harnessing Light: Optical Science and Engineering for the 21st Century One reason optics educational programs achieve success in teaching across these boundaries is that educators in optics have an excellent network to help them with their work. Key to this network are the two major professional societies, OSA and SPIE, and a number of other societies that have sections devoted to optics or have optics as a parallel track to their main thrust. Recognizing the breadth of optics, the societies have formed the Coalition for Photonics and Optics to serve the broader community of optics professionals and to inform government agencies, educational institutions, and industry about the future importance of optics. The professional societies should work to strengthen optics as a recognized crosscutting area of science and technology through the recently established Coalition for Photonics and Optics. The society structure is supplemented by a number of international conferences on all areas of optics, including optics education. There are two recognized approaches to the teaching of optics. One is a broad program of study, at an institute that recognizes optics as a separate discipline, covering the field with components in geometrical, physical, and quantum optics. The other model is an extended set of course sequences that bridge departments and schools and offer study in subfields of optics, such as lasers, image processing, electronic imaging, or electro-optics. The multidisciplinarity of the latter approach is a great strength, but the narrowness of some programs can be a disadvantage if graduates think they have been educated in optics when in fact they have been exposed only to certain subfields. No physics department would limit its program of study to solid-state physics or to quantum mechanics, and no electrical engineering department would teach courses only in circuits. Universities should encourage multidisciplinarity in optics education, cutting across departmental boundaries, and should provide research opportunities at all levels, from the bachelor of science to the doctorate and from basic science to applied technology. These diverse optics programs are sufficient to meet current needs and probably also have the capacity and flexibility to meet future needs. The continued evolution of the field and increasing demand by industry may result in a need to extend optics education at the bachelor's or associate's degree level. There is no apparent need to create new programs of teaching in optics at the advanced level. The state of education and training in optics is generally healthy at present. It has been traditional for many Ph.D. graduates in optics to go on to work in industry and for the government, unlike some other disciplines in which the "normal" track for a Ph.D. graduate is in academia. Thus, optics education is already meeting the goals stated in a recent report of the Committee on Science, Engineering, and Public Policy (COSEPUP, 1995). The same can be said of most optics master's programs. These programs are styled after engineering programs but with some of the attributes

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Harnessing Light: Optical Science and Engineering for the 21st Century that promote "adaptability and versatility as well as technical proficiency," as called for by COSEPUP. Master's programs in optics are independent programs with specific curricular goals, not just a set of courses on the way to a Ph.D. Thus, the field is also meeting many of the goals suggested in a recent article "Mastering Engineering" (Fitzgerald, 1996). Continuing Education The field is fortunate to have an excellent set of continuing education opportunities provided by academic institutions and national societies. Courses in continuing education offered by the OSA, SPIE, and other societies cover a wide spectrum from basic science to engineering to technology. They also include professional development courses in such subjects as business, management, ethics, marketing, and patents. Courses are offered in conjunction with national meetings and are also available by videotape and broadcast. They are supplemented by excellent written materials prepared through the societies' publication programs. The professional societies should continue to expand their commitment to professional education in optics. Summary and Recommendations Broad Issues Research in optics cuts across disciplinary boundaries and enables advances in many other areas of research as well as commercial applications that are important for the nation's future growth and prosperity. As indicated by the response to the NSF optical science and engineering initiative in 1995, there is high demand and strong competition for optics research funding. However, optics often has difficulty finding research support in the federal agencies, despite the scientific excitement in the field and its significant and growing economic importance, because of its multidisciplinary and enabling character, which contrasts with the agencies' structure by discipline or by mission. Optics involves multiple agencies and multidisciplinary collaboration and support. Optics is a rapidly growing crosscutting area of science and technology that is ripe for investment at a level comparable to the support of high-performance computing and communications. In the United States the combination of research and education provides the joint benefit of the discovery of knowledge and the education of students. Support for research in the nation's universities is 0.5% of the GDP, the lowest investment rate of advanced industrialized nations. Fundamental scientific and engineering research laid the basis of understanding required for the discovery of the laser in 1960, a discovery that has ultimately led to significant economic and social benefits for

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Harnessing Light: Optical Science and Engineering for the 21st Century the nation. Continued investments in research and development have led to widespread applications of lasers and related technologies in basic science, engineering, medicine, communications, information storage, information display, and entertainment. Multiple government agencies should form a working group to collaborate in the support of optics, in a crosscutting initiative similar to the earlier one for high-performance computing and communications systems. The National Science Foundation should develop an agency-wide, separately funded initiative to support multidisciplinary research and education in optics. The Department of Commerce should explicitly recognize optics as an integrated area of knowledge, technology, and industry and should structure its job and patent databases accordingly. Research Opportunities Quantum, Atomic, and Biological Optics Light has historically been used to probe matter via spectroscopy. Important advances in spectroscopy techniques continue to be made. In addition, light is now used to manipulate atoms, molecules, and submicron particles. This control opens up possibilities for applications such as atomic-scale lithography and information storage. Laser-cooled atoms are being used to develop the next generation of atom clocks. Atom mirrors, beam splitters, and lenses have led to some of the most sensitive inertial sensors such as accelerometers and gyroscopes. Atoms laser-cooled to nanokelvin temperatures have formed a new state of matter, the Bose-Einstein condensate. Lasers have been used to create a form of light for which the fundamental noise limits of the Heisenberg uncertainty principle can be manipulated to enable more precise measurements. The unavoidable, quantum-limited perturbation of a physical system during a measurement can be modified. The disturbance of the quantum variable of interest can be minimized by shifting the effect of the measurement to another quantum degree of freedom. Quantum states with several degrees of freedom can be engineered so that the quantum phase of the entire system can be preserved. Although practical general-purpose quantum computers are unlikely to be developed, this research is at the forefront of the exploration of more complex quantum systems. Recombinant DNA techniques have been used to instruct cells to manufacture proteins with fluorescent tags. The intercellular motion of these labeled proteins can be tracked with an optical microscope. The optical microscope and new variations such as the confocal microscope and the near-field scanning microscope are undergoing rapid technological development.

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Harnessing Light: Optical Science and Engineering for the 21st Century This progress is further aided by the introduction of sensitive photon detectors and computer processing of images. Laser-based optical tweezers can manipulate submicron-sized objects such as organelles within live cells. This tool has also been used to manipulate single biological molecules; molecular forces and displacements during an isolated molecular event can now be measured. Light is now used to control atoms, which opens up possibilities for new applications from laser-cooled atomic clocks to gyroscopes to gravitometers. Laser control of atoms has created a new form of matter, the Bose-Einstein condensate, in which all atoms occupy the same atomic state. Light control of atoms allows quantum states to be engineered, which may open up new possibilities for applications of complex quantum systems. The new fluorescent dyes and dye-labeling techniques allow the detection of a single molecule, which has important applications in chemistry, biology, and medicine. With these techniques, coupled with recent advances in microscopy and sensitive light-based techniques for detection and control, measurement and control at the single-molecule level appear possible. NSF should recognize the dramatic new opportunities in fundamental research in atomic, molecular, and quantum optics and should encourage support for research in these areas. Femtosecond Optics Optics has opened the femtosecond time domain to science and technology through the use of lasers that produce ultrashort pulses of light. Extremely intense optical fields, made possible by the amplification and compression of femtosecond laser pulses, are creating new opportunities in physics and medicine. Femtosecond sources of high average power offer dramatic advantages for laser processing of materials. Femtosecond laser pulses, because they are coherent optical waveforms, offer new and unique capabilities for manipulating molecules to produce new chemistry and biochemistry. Femtosecond lasers open the possibility of generating subfemtosecond x rays for time-resolved studies of biological structures. The rapid advance of femtosecond technology is being driven by the invention of new techniques for pulse generation and new all-solid-state laser systems. Low-cost femtosecond sources are key to the rapid application of these unique optical sources. Optical fiber communication technology is already a major beneficiary of short-pulse laser research and it should benefit further from rapid progress in the generation of ultrashort pulses. Many new applications for femtosecond lasers are based on properties other than ultrahigh speed. Laser acceleration benefits from the high peak power of focused femtosecond lasers. Terahertz imaging and optical coherence tomography (see Chapter 2) are two examples of new applications opened by femtosecond lasers.

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Harnessing Light: Optical Science and Engineering for the 21st Century Femtosecond optics is an important developing science and technology that is opening new opportunities for advances in physics, chemistry, biology, and medicine. New, unexpected commercial applications enabled by femtosecond lasers are beginning to emerge. These applications and others could be greatly stimulated by the development of highly reliable, low-cost femtosecond sources. Femtosecond optics and sources offer an opportunity for dramatic impact on science and technology. Agencies should focus attention on this opportunity and encourage innovative work in this cutting-edge field. Semiconductor and Advanced Solid-State Lasers The growth and market size of lasers and applications track the growth and market size of computers with a 15-year delay, and the market for lasers and applications is expected to grow from about $3 billion per year to greater than $20 billion per year in the coming decade. Laser diodes are efficient, reliable sources of coherent light that are mass produced. Increasing production volumes with decreasing costs per laser diode will lead to expanding markets. Light-emitting diodes are lower in power and efficiency than laser diodes, but their very low cost enables applications in markets that exceed $3 billion. Organic and porous silicon-based LEDs offer the promise of a low-cost, paper-like display that can be addressed by a pocket-sized optical-based information storage unit. Companies in the United States lead the world as commercial suppliers of high-power laser diodes. However, R&D investments in Europe and in Japan are challenging that lead. The current market for solid-state lasers is $394 million and is growing at more than 20% per year. Advanced solid-state lasers now operate at power levels in excess of 1 kW and are finding applications in cutting, welding, hole drilling, surface hardening, reprographics, and medicine. Japan and Germany have initiated R&D programs for advanced solid-state lasers funded at levels of $500 million and $100 million over the next 5 years to capture the multibillion-dollar market projected for the next decade. Major science projects in the United States, such as the LIGO and NIF projects, are technology drivers for advanced solid-state lasers. Research on new and improved lasers is a priority recommended in the 1994 FAMOS report (NRC, 1994). Semiconductor laser diodes, LEDs, and advanced solid-state lasers are important technologies that enable applications critical to the nation. Light sources based on solid-state technologies represent an important opportunity for R&D investment with very high leverage for return on investment. Investment in this technology has declined in the United States, whereas it has accelerated in both Germany and Japan. R&D investment in semiconductor and advanced solid-state lasers is essential if the United States is to retain technological leadership.

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Harnessing Light: Optical Science and Engineering for the 21st Century R&D and applications of solid-state lasers are cross-disciplinary and should be supported by a special initiative involving multiple agencies. Advanced Materials for the Generation and Control of Light Frequency extension of laser sources by nonlinear crystals is critical to many applications that range from laser radar, to remote atmospheric sensing, to laser projection displays, to lasers for medical applications. The recent advances in engineered nonlinear materials and the breakthrough in cost reduction by a factor of 1,000 to less than $1 per nonlinear crystal "chip" open the possibility of commercial applications of frequency-shifted solid-state lasers. Structured materials have created new opportunities for advanced optical technologies. Future realization of structures with photonic bandgap properties would have major impact on optics and optoelectronics industries. New fabrication techniques allow the control of light using lenses that are mass produced at low cost using gradient index materials, diffractive optics, and aspheric lenses. New materials are critical to the future progress in the extension of laser capability by frequency conversion. Materials research often takes a decade or longer before the material is developed to the degree required for applications. The long lead time for materials research has to be recognized in the support of research programs. Advances in materials enable new approaches to devices and open new application possibilities. Engineered nonlinear materials, structured dielectrics, and nanostructured quantum-well semiconductors are advanced materials capabilities that have significant impact on optical science and engineering. Progress in materials science and engineering is critical to progress in optics. The committee recommends that DARPA coordinate and invest in research on new optical materials and materials processing methods with the goal of achieving breakthrough capability though engineered semiconductor, dielectric, and nonlinear optical materials. Extreme Ultraviolet and X-Ray Optics There is considerable interest in developing EUV and x-ray microscopes for higher-resolution imaging of biological and physical structures. X-ray microscopes allow atomic species to be detected by tuning the wavelength to the atomic resonance. Lithography is moving from the UV to the EUV and soft x-ray wavelengths to meet the demand for smaller feature size in future semiconductor devices. There is a need for EUV and x-ray sources that are laboratory scale for research and manufacturing activities. EUV and soft x-ray optics are providing new opportunities in broadly based science and technology, with potential impact for the manufacture of turn-of-the-century semiconductor electronics devices through the application of EUV and soft x-ray lithography.

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Harnessing Light: Optical Science and Engineering for the 21st Century Multiple agencies with interest in the crosscutting science and technology of EUV and soft x-ray optics and techniques should encourage research in this area because of the substantial potential economic payback in the near future. Education in Optics There is a recognized integrated body of knowledge that constitutes optics. Educational institutions have recognized that this body of knowledge must be taught in an integrated and unified way. Professional societies have recognized that optics is a broad area of knowledge and practice by forming a Coalition for Photonics and Optics. Unlike traditional departmental disciplines in science and engineering, optics is involved in both science and engineering and hence cuts across traditional educational boundaries from very basic academic sciences to applied sciences to technology to engineering systems in an integrated manner. Academic educational programs thrive and are effective when students are exposed to and involved with research activity. This is true at the bachelor's level but vital at the master's and doctoral levels. Research activity in optics covers the full spectrum from basic to applied science to engineering to technology. Students educated and trained in optics are in demand at this time in many fields of optics. The diversity of the U.S. educational system, coupled with the flexibility of scientists and engineers to change direction, allows the supply of students educated in optics to meet projected demands in the foreseeable future. The quality and diversity of continuing education courses offered by professional societies is first rate and should be continued. Excellent mainstream optics programs are in place that have the ability and flexibility to meet perceived national needs. A national program to establish new teaching centers is not required, but support for the existing structure should not be permitted to erode. NSF should develop an agency-wide, separately funded initiative to support multidisciplinary research and education in optics. Opportunities include fundamental research in atomic, molecular, and quantum optics; femtosecond optics, sources, and applications; solid-state laser sources and applications; and EUV and soft x-ray optics. The professional societies should work to strengthen optics as a recognized crosscutting area of science and technology through the recently established Coalition for Photonics and Optics. They should evaluate educational programs in optics and jointly produce an annual guide. The professional societies should continue to expand their commitment to professional education in optics.

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Harnessing Light: Optical Science and Engineering for the 21st Century Universities should encourage multidisciplinarity in optics education, cutting across departmental boundaries, and should provide research opportunities at all levels, from the bachelor of science to the doctorate and from basic science to applied technology. References Anderson, S.G. 1997. Review and forecast of laser market. Laser Focus World 33(1):72. Armstrong, J.A., N. Bloembergen, J. Ducuing, and P.S. Pershan. 1962. Interactions between light waves in a nonlinear dielectric. Phys. Rev. 127:1918. Collins, R.T., P.M. Fauchet, and M.A. Tischler. 1997. Porous silicon: From luminescence to LEDs. Phys. Today (January):24. Committee on Science, Engineering, and Public Policy. 1995. Reshaping the Graduate Education of Scientists and Engineers. Washington, D.C.: National Academy Press. Fitzgerald, N. 1996. Mastering engineering. ASEE Prism 5:25-28. Jackson, I.W. 1848. An Elementary Treatise on Optics. New York: A.S. Barnes and Company. Joshi, C.J., and P.B. Corkum. 1995. Interactions of ultra-intense laser light with matter. Phys. Today (January):36-43. Kido, J., M. Kimura, and K. Nagai. 1995. Multilayer white light organic electroluminescent device. Science 267:1332. Kingslake, R., and H.G. Kingslake. 1970. A history of the Institute of Optics. Appl. Opt. 9(4):789-796. National Research Council. 1994. Atomic, Molecular, and Optical Science: An Investment in the Future. Washington, D.C.: National Academy Press. National Science Board. 1996. Science and Engineering Indicators 1996, NSB 96-21. Washington, D.C.: U.S. Government Printing Office. National Science Foundation. 1994. Optical Science and Engineering: New Directions and Opportunities in Research and Education, NSF 95-34. Washington, D.C. Optical Society of America. 1992. International Guide to Optics Courses and Programs, 1992, 3 vols. Washington, D.C. SPIE. 1996. Optics Education 1996: Annual Guide to Optics Programs Worldwide. Bellingham, Wash.: SPIE Publications. Thompson, B.J. 1996. 1995 in review. Opt. Eng. 35(2):325-326. Thompson, B.J. 1997. 1996 in review. Opt. Eng. 36(2):297-299.