Caltech applied physicists invent waveguideto bypass diffraction limits for new optical devices

Four hundred years ago, a scientist could peer into one of the newfangled optical microscopes and see microorganisms, but nothing much smaller. Nowadays, a scientist can look in the latest generation of lens-based optical microscopes and also see, well, microorganisms, but nothing much smaller. The limiting factor has always been a fundamental property of the wave nature of light that fuzzes out images of objects much smaller than the wavelength of the light that illuminates those objects. This has hampered the ability to make and use optical devices smaller than the wavelength. But a new technological breakthrough at the California Institute of Technology could sidestep this longstanding barrier.

Caltech applied physicist Harry Atwater and his associates have announced their success in creating "the world's smallest waveguide, called a plasmon waveguide, for the transport of energy in nanoscale systems." In essence, they have created a sort of "light pipe" constructed of a chain-array of several dozen microscopic metal slivers that allows light to hop along the chain and circumvent the diffraction limit. With such technology, there is the clear possibility that optical components can be constructed for a huge number of technological applications in which the diffraction limit is troublesome.

"What this represents is a fundamentally new approach for optical devices in which diffraction is not a limit," says Atwater.

Because the era of nanoscale devices is rapidly approaching, Atwater says, the future bodes well for extremely tiny optical devices that, in theory, would be able to connect to molecules and someday even to individual atoms.

At present, the Atwater team's plasmon waveguide looks something like a standard glass microscope slide. Fabricated on the glass plate by means of electron beam lithography is a series of nanoparticles, each about 30 nanometers (30 billionths of a meter, in other words) in width, about 30 nanometers in height, and about 90 nanometers in length. These etched "rods" are arranged in a parallel series like railroad ties, with such a tiny space between them that light energy can move along with very little radiated loss.

Therefore, if light with a wavelength of 590 nanometers, for example, passes through the nanoparticles, the light is confined to the smaller dimensions of the nanoparticles themselves. The light energy then "hops" between the individual elements in a process known as dipole-dipole coupling, at a rate of propagation considerably slower than the speed of light in a vacuum.

In addition to their functionality as miniature optical waveguides, these structures are also sensitive to the presence of biomolecules. Thus, a virus or even a single molecule of nerve gas could conceivably be detected with an optical device designed for biowarfare sensing. The potential applications include electronic devices that could detect single molecules of a pathogen, for example.

The ultrasmall waveguide could also be used to optically interconnect to electronic devices, because individual transistors on a microchip are already too small to be seen in a conventional optical microscope.

A description of the device will appear in the April 2003 issue of the journal Nature Materials. The other Caltech authors of the paper were Stefan A. Maier, a former graduate student and now postdoctoral researcher at Caltech, who was responsible for the working device, and Pieter G. Kik, also a postdoctoral researcher. Other authors were Sheffer Meltzer, Elad Harel, Bruce E. Koel, and Ari A.G. Requicha, all from the University of Southern California.

The nanoparticle structures were fabricated at the Jet Propulsion Laboratory's facility for electron beam lithography, with the help of JPL employees Richard Muller, Paul Maker, and Pierre Echternach.

The research was sponsored by the Air Force Office of Scientific Research and was also supported in part by grants from the National Science Foundation and Caltech's Center for Science and Engineering of Materials.

Contact: Robert Tindol (626) 395-3631


Caltech applied physicists create ultrahigh-Q microcavity on a silicon chip

In an advance that holds promise for integrating previously disparate functions on a chip, applied physicists at the California Institute of Technology have created a disk smaller than the diameter of a human hair that can store light energy at extremely high efficiency. The disk, called a "microtoroid" because of its doughnut shape, can be integrated into microchips for a number of potential applications.

Reporting in the February 27, 2003, issue of the journal Nature, the Caltech team describes the optical resonator, which has a "Q factor," or quality factor, more than 10,000 times better than any previous chip-based device of similar function. Q is a figure-of-merit used to characterize resonators, approximately the number of oscillations of light within the storage time of the device.

The devices store optical energy by resonant recirculation at the exterior boundary of the toroid and achieve Q factors in excess of 100 million. In general, resonators whether mechanical, electronic, or optical have many applications. TV tuners and quartz crystals in a wristwatch are examples of resonators at radio frequencies; at optical frequencies, resonators are used in filters, sensors, and quantum optics.

Attaining ultrahigh-Q and fabricating the resonators on a chip have so far been mutually exclusive. Only rather exotic structures, like droplets or microspheres, have exhibited the atomically smooth surfaces needed for ultrahigh-Q. Due to a novel fabrication step, it is now possible to achieve both high Q and atomically smooth surfaces at the same time and to bring two worlds together.

The fabrication procedure uses lithography and etching techniques on a silicon wafer in a manner similar to process steps used for making microprocessors and memories. Thus, the resonators can be integrated with the circuitry of a chip, with lab-on-a-chip functions, or even with other optical components. Wafer-scale processing methods also enable their production in large quantities, an important feature in many applications, like biosensing, where low-cost, field deployable sensors are envisioned.

The microtoroids were fabricated in the lab of Kerry Vahala, who is Jenkins Professor of Information Science and Technology and professor of applied physics at Caltech. Vahala is co-inventor of the device, along with his graduate students Deniz Armani, Tobias Kippenberg, and Sean Spillane.

"This is the first time an optically resonant device with an ultrahigh-Q has been fabricated on a chip," says Vahala.

Vahala says his group is exploring ways to further increase the Q value of these devices as well as to further reduce their size. He believes Q values in excess of 1 billion in even more compact toroids will soon be possible. Last year, in the February 7, 2002, issue of Nature, the Vahala group reported an efficient nonlinear wavelength source using ultrahigh-Q resonators. His group is now investigating microchip-toroid versions of these nonlinear sources that may one day be used in communications systems.

The work was supported by Caltech's Lee Center for Advanced Networking and DARPA.

Contact: Robert Tindol (626) 395-3631


Fuel Cells: Powering Progress in the 21st Century

PASADENA, Calif. – Continuing tensions in the Middle East make it clear that we face long-term challenges in meeting our ever increasing energy demands, while still maintaining the quality of our natural environment and ensuring our national security. Fuel cells offer a possible solution, but, before they meet their potential, many technical hurdles remain.

On Wednesday, January 29, Dr. Sossina M. Haile, an associate professor of materials science at the California Institute of Technology, will provide a brief overview of current fuel cell technology, then discuss her own work in this promising area. Whereas the most common type of fuel cell--the kind that powers prototype cars--is a polymer electrolyte fuel cell, Haile is taking a different tack, developing an alternative type of fuel cell based on a so-called solid acid.

Haile will describe the recent breakthroughs in this new technology and the challenges that remain. The ultimate goal, of course, is that such engineering in materials science may someday mean a fuel cell in your automobile, your laptop, or your home.

Caltech has offered the Watson Lecture Series for almost 80 years, since it was conceived by the late Caltech physicist Earnest Watson as a way to explain science to the local community. The lecture will take place at 8 p.m. in Beckman Auditorium, which is located near Michigan Avenue south of Del Mar Boulevard, on Caltech's campus in Pasadena. Seating is available on a free, no-ticket-required, first-come, first-served basis, beginning at 7:30 p.m. Parking is available in the lots south of Del Mar Boulevard between Wilson and Chester Avenues, and in the parking structures at 341 and 405 South Wilson and 370 South Holliston Avenue.

For more information, call 1(888) 2CALTECH (1-888-222-5832) or (626) 395-4652. Persons with disabilities: (626)-395-4688 (voice) or (626)-395-3700 (TDD).

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Caltech Students to Clash--Robotically

Gears will grind, shafts will spin, and who-knows-what the slat from a Venetian blind will do as undergraduates from the California Institute of Technology attempt to "bag the flag" in Caltech's 18th annual Engineering Design Contest.

The competition between machines, hand-built by undergraduates, will take place at 2 p.m. December 5 in Beckman Auditorium, and is open to the Caltech community. Due to limited seating and the expected large campus turnout, the general public is not invited for this event. The media, however, are invited to attend and cover the event, which should last about 90 minutes.

The contest, which indeed is usually observed by a packed crowd of somewhat-raucous students, is the culmination of a quarter's worth of hard work for the 24 juniors and seniors enrolled in this year's Mechanical Engineering 72 class. On October 1 each student was presented with a so-called "bag of junk"--motors, gears, springs, screws, bearings, and yes, go figure, a slat from a Venetian blind--to use in assembling their machines. At the same time, they were presented with the details of this year's contest: In teams of two, they must design and build separate devices that will work with their partner's device to remove a 10-inch-tall flag from its base. One of the gadgets must then transport the flag across the center line of a six-and-a-half foot diameter arena and plant the flag in their opponent's base, thus "bagging" the flag. The teams have 44 seconds to do it; the first team to plant the flag wins.

The course was originated by Caltech's Erik Antonsson, a professor of mechanical engineering and the chief technologist at the Jet Propulsion Laboratory. The course is being taught by instructors Dr. Maria Yang and Dr. Curtis Collins. In the course's introduction, they warn the students that "your moment of glory (on stage) is only made possible by the expenditure of many hours of planning, designing, building, testing, failing, repairing, rebuilding, modifying (crying, laughing, screaming, chuckling, wailing, cheering, sweating. . .)." All together, the students are expected to put in 150 hours of work during the ten-week term on the design, fabrication, testing, and fine-tuning of their device.

While the annual contest is a highlight of the Caltech academic year for students and faculty alike, the object, of course, is to learn something about designing, under deadline, for the real world.

"Caltech students have a well-earned reputation for being able to solve just about any problem presented to them, and this course pushes those abilities to the limit," says Yang. "Students not only generate concepts and design solutions, but they get some serious hands-on experience building and testing, building and testing, and then building and testing some more."

The event is sponsored by Applied Materials, BSST a subsidiary of Amerigon, Dr. David and Mrs. Barbara Groce, Honeywell, idealab!, Mabuchi Motor Co., Northrop Grumman Corp., the San Diego Foundation, and the Toro Company.

MEDIA ACCESS: The contest is open to the news media. Media will have special seating in the front of the auditorium. To ensure that the hundreds of students, faculty, and staff have a clear view of the contest, we ask that the media not stand on or in front of the stage.

Note to Editors: Attached is a jpeg of third-year mechanical engineering student Salomon Trujillo and his machine.

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Wu elected to Chinese Academy of Science

PASADENA, Calif. — The Chinese Academy of Sciences (CAS) has announced that Theodore Yaotsu Wu, professor, emeritus, of engineering science at the California Institute of Technology, was elected as a Foreign Member of the Academy.

Wu, 78, who earned degrees from Shanghai Jiaotong University in China, Iowa State University, and a Ph.D. in aeronautics from Caltech in 1952, is being recognized for his work in fluid mechanics and for his international academic interaction and collaboration, especially with CAS.

This year the Academy offered memberships to Wu and six others, bringing the total number of foreign members worldwide to 41.

The CAS elects foreign members to assist in the future development of, and advances in, science and technology, education, research, and interaction between international scholars.

Wu, the author of several books and more than 150 scholarly papers, has contributed to the understanding of biophysical, geophysical, and physical fluid dynamics and has directed several research groups in the fields of hydrodynamics, and nonlinear ocean waves.

Wu is also a member of the National Academy of Engineering and Academia Sinica, a John Simon Guggenheim Fellow, and a fellow of the American Physical Society and Japan Society of Promotion of Science. In 1993, he was honored with the American Physical Society's Fluid Dynamics Prize, which is awarded annually to an individual for major contributions to fundamental fluid dynamics made during a career of outstanding work in the United States.

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White House names Caltech's Erik Winfree as Presidential Early Career Award winner

Erik Winfree, a computer expert who hopes someday to use DNA molecules to perform computations, has been named a 2002 winner of the Presidential Early Career Award for Scientists and Engineers (PECASE). The honor, announced June 27 by the White House, is made each year to young American scientists and engineers whose innovative work is expected to lead to future breakthroughs.

Winfree, 32, is an assistant professor of computer science and computation and neural systems at the California Institute of Technology. A Caltech graduate, he has been a member of the faculty since 1999.

"Our group is interested in biomolecular computation: how systems of biomolecules, such as DNA and enzymes, can process information and carry out algorithms," Winfree explains on his lab's Web site. "While our theoretical studies are wide-ranging, our experimental efforts focus on coaxing DNA to perform algorithmic tricks."

The PECASE is the third major award Winfree has won in the last two years. In 2000 he was named a MacArthur Fellow in the program often referred to as the "Genius Grants." In addition, he was awarded a $500,000 Faculty Early Career Development (CAREER) award from the National Science Foundation in 2001, and in 2000 was on MIT's first list of TR100 innovators.

A native of Chicago, Winfree earned his bachelor's degree in mathematics from the University of Chicago in 1991, and studied computation and neural systems under John Hopfield and Al Barr at Caltech from 1992 to 1998. He also was a postdoctoral scholar at Princeton and a visiting scientist at MIT.

The PECASE awards were created in 1996 by the Clinton Administration "to recognize some of the nation's finest junior scientists and engineers and to maintain U.S. leadership across the frontiers of scientific research."

Contact: Robert Tindol (626) 395-3631

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Alquist Medal for earthquake safetyawarded to Caltech engineer

Wilfred Iwan, a professor of applied mechanics at the California Institute of Technology, has been named the 2002 recipient of the Alquist Medal by the California Earthquake Safety Foundation.

Iwan, who is also director of Caltech's Earthquake Engineering Research Laboratory, was chosen for the award in honor of "his lifetime of service to the profession of structural engineering and its application to the safety of the people of California and the world," the foundation announced.

The award was presented February 7 in Long Beach at the annual meeting of the Earthquake Engineering Research Institute.

Iwan, a Caltech alumnus, has been a member of the faculty since 1964. His research interests include the theory of vibrations, modeling of structural systems, the earthquake response of structures as well as nonstructural components such as piping, and offshore engineering for better seismic design.

In addition, Iwan has been involved in the development of national and international strategies for the deployment of strong-motion earthquake instruments, including real-time monitoring and early-warning systems. He introduced the concept of "drift demand spectrum" as a means of measuring the damage potential of strong earthquake ground motions, and has worked toward improving both seismic instrument design and the interpretation of data.

He has been involved with the California Seismic Safety Commission in developing a comprehensive earthquake risk-reduction plan for California.

Iwan has served on a number of commissions and boards, including the National Research Council's Board on Natural Disasters, the National Research Institute for Earth Science and Disaster Prevention of Japan's Evaluation Panel, the U.S. Department of Energy's New Production Reactors Senior External Events Review Group, the U.S. Nuclear Regulatory Commission's Review Panel for Seismic Criteria for Nuclear Plant Piping Systems, and the Consortium of Universities for Research in Earthquake Engineering, of which he is a director and founding president.

He holds several patents, and is author or coauthor of numerous publications on earthquake engineering and seismology.

CONTACT: Robert Tindol (626) 395-3631

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Caltech's annual machine competitionto be held December 6

Caltech mechanical engineering students are putting in quality tool time these days to prepare for the annual ME 72 engineering design contest, a celebrated campus event in which teams of robot rovers are pitted against each other in a test of engineering design acumen, strategy, teamwork, and sheer driving skill.

This year's contest, the 17th in the annual series, will be held at 2 p.m., Thursday, December 6, in Beckman Auditorium on the Caltech campus. The design and construction of a machine is an important requirement for the Mechanical Engineering 72 design course, and the annual event has become an eagerly anticipated campus tradition among students and faculty. The media are invited to attend and cover the event, which should last about 90 minutes.

At the beginning of the 2001 fall term, the students registering for Mechanical Engineering 72 were given a design task, a "bag of junk," and 10 weeks to design and build a machine they judged capable of performing an assigned feat during a public contest at the end of the term. The students, paired up in teams, have now finished designing, prototyping, fabricating, assembling, testing, debugging, and tuning their machines and are ready to find out which team's machines are tops.

This year's contest is somewhat different in that the machines will compete on a curved, sloping series of steps, rather than a horizontal table as in many previous years, said Erik Antonsson, a professor of mechanical engineering at Caltech who is the originator of the design contest.

"The task this year is to push as many hockey pucks as possible up to the highest sloping step possible, Antonsson said. "You get more points for putting a puck higher up the steps, but you also have to contend with a steeper slope.

"Also, for the second straight year we're using wireless power controllers, so students will control their vehicles by radio instead of by an attached umbilical cord."

Though the contest is entertaining for onlookers, Antonsson said the motivation is to teach students how to design complicated devices that can hold up—and perhaps even perform admirably—in the real world.

"Engineering is primarily the process of creating new things to solve problems," Antonsson said. "This course and contest is one attempt to provide students with a real-world opportunity to learn about the design of new things and the solution of open-ended, ill-defined problems."

The event is sponsored by Schlumberger, Allied Signal, Northrop Grumman Corp., Applied Materials, General Motors, the San Diego Foundation, idealab!, and Hewlett-Packard Company (San Diego Division).

MEDIA ACCESS: The contest is open to the news media and Caltech community. Press will have special seating in the front rows on the left side of the auditorium, and will have supervised access to the stage and student preparation room during breaks. To ensure that the hundreds of students, faculty, and staff have a clear view of the contest, we ask that the press not stand on or in front of the stage.

Contact: Robert Tindol (626) 395-3631


Machinist provides undergrads withquality time in the Caltech shop

Machinist John Van Deusen looks on approvingly as two Caltech undergraduates prepare to see how well their new robot climbs a curved wall.

The robot performs its task admirably—not necessarily a foregone conclusion in the Caltech machine shop, where dysfunctional robots have been known to come into creation. Van Deusen, ever the diplomat, passes by without commenting one way or the other.

"In ME 72 we bite our tongues a lot," Van Deusen says later. The robot the two undergrads have built is pretty much a set of felt-lined caterpillar treads linked by a single aluminum bar.

Controlled by radio and powered by small electric motors, the device exists for the purpose of racing up an ever-steepening wall, retrieving as many hockey pucks resting on the wall as possible, and, ideally, winning the coveted first-place award in the famed Mechanical Engineering 72 contest.

Van Deusen's purpose, on the other hand, is to show the students how to use the machines, give them advice on how best to achieve what they are trying to achieve, and makes sure they use the high-powered equipment of the machine shop safely.

Van Deusen is the guy who consults with the students as they build their machines for the ME 72 competition each December—a public contest that attracts virtually the entire Caltech campus and usually a fair number of Los Angeles and national media outlets. As manager of the Caltech machine shop, he provides instruction on how to do the fixing and making that will be very much a part of every student's life, to one degree or another. After all, mechanical engineering is the process of creating a new thing to solve an often poorly defined and open-ended problem—be it exploration of a new world or mechanical delivery of a new drug.

Therefore, even at a highly analytical school like Caltech, fledgling mechanical engineers find that they are most likely to spend their careers at the cutting edge if they are familiar with . . . well, the actual cutting edge. And that's where Van Deusen's expertise is especially valuable, says Caltech mechanical engineering professor Erik Antonsson.

"Being a mechanical engineer without knowing your way around a machine shop would be like being an MD without ever having been inside a clinic," says Antonsson, originator and guru of the ME 72 contest. "It really helps the students to do some actual machining, and John is really good at helping them build some amazing skills."

The whole point of the design contest, according to Antonsson, is to nurture the ability of future engineers to design the best possible machine to accomplish an arbitrary task. Each year Antonsson comes up with a contest in which two-person teams build a machine to perform an offbeat task such as gathering Ping-Pong balls, move disks across a barrier—or in the case of this year's contest, collecting hockey pucks off a wall. If the students have come up with a viable design—and if they've learned their machining skills well from Van Deusen—they may rack up sufficient points to win the annual public contest, which for years has been one of the most celebrated events of the academic year.

Though it would seem that a design from one year might prove to be an all-around winner in successive years, Antonsson has deviously assured that such is unlikely to happen. Lower-division students can indeed learn a lot by watching the predominantly senior ME 72 class at work, but they can only learn generic rules of the game. The following year's task will assuredly be so different in design that everyone in class will be forced to go back to the drawing board, so to speak.

The only parameters that seem to be repeated year to year is Antonsson's practice of providing each team with a bag of aluminum sheets and bars, a few cogs, axles, some clear acrylic material, a few small electric motors, wires, and so on—a bag of "junk," as he calls it—and the injunction to go to Van Deusen's subbasement shop and get busy with the mills and lathes. Thus, Van Deusen is essentially one of the instructors for the ME 72.

"In ME 72, we tell them only how to make the parts. We try not to influence them on design questions, but on manufacturing questions, we say, 'Hey, come to us.'"

When asked if he often knows who will likely win the annual contest, Van Deusen reluctantly admits he usually has a pretty good idea. Because of his long experience as a machinist, he can usually spot a good design as well as a bad one.

Van Deusen's personal experience with novel designs is grounded in the aerospace industry. The most unique thing he ever personally built, he says, is the umbilical for the Space Shuttle while he was employed by Hansen Engineering in Harbor City.

The umbilical, he explains, is the last link to break away when a shuttle launches. The device is a solid piece of aluminum four feet wide and five feet long, with a thickness of 13 inches and an intricate design. The umbilical required half a year to construct, and that included writing programs for the early-generation numerically controlled mill.

"We all held our breaths the first time a shuttle went off," Van Deusen says. "We had been saying that if we saw a bunch of wires dragging along behind the shuttle, we wouldn't go back to work the next day."

When the Southern California aerospace economy went soft in the early 1990s, Van Deusen found a job as head of the machine shop at Caltech, and he's been there ever since. Though he cut his college education short after a couple of years of community college, he's now back at Cal State Long Beach and working on a bachelor's degree in vocational education.

Though he originally thought he wanted to be a pharmacist, Van Deusen says he thoroughly enjoys working in machine shops and has no regrets about his choice of careers.

"I eventually asked myself if I wanted to go to USC for six years and be a night pharmacist at Sav-on," he says. "I decided I liked the mechanical aspect of being a machinist, and I still do."

As for his Caltech job, Van Deusen says he especially appreciates the steep learning curve of the typical Caltech undergraduate. Virtually all of them are quick studies in the shop as well as in class, he says.

"For these students, learning fabrication skills is not hard at all. And as far as learning the theory, it's nothing for them," he says. "But they're not precision machinists, and to manufacture things, you have to learn how to do things properly, or else axles won't match up, or edges won't meet."

Antonsson says Van Deusen's knack with the students is a key to the success of the annual ME 72 endeavor. "He's very thoughtful, and really tuned to the students.

"Every year about this time he puts up a Christmas tree and encourages students to decorate it with all kinds of chips and things that come off their machines while machining," Antonsson says.

"That goes to show how he really makes the whole shop environment a welcoming home."

Contact: Robert Tindol (626) 395-3631


Environmental Study of Local Area Conducted by Caltech Team

PASADENA, Calif.— California Institute of Technology researchers have received a $100,000 grant from the Alice C. Tyler Perpetual Trust to study the human impact on land and water in the San Gabriel Valley and San Gabriel River watershed. Ecosystems bordering major metropolitan areas are subject to intense pressures from pollutants produced by transportation, industrial activities, power generation, and recreational activities. This project will measure and document these environmental changes in order to predict future impacts.

The research project, "Environmental Quality Near Large Urban Areas," is being coordinated by Janet Hering, associate professor of environmental engineering science at Caltech. Other members of the group include Michael Hoffmann, the James Irvine Professor of Environmental Science; James Randerson, assistant professor of global environmental science; and Paul Wennberg, professor of atmospheric chemistry and environmental engineering science.

The project will also teach Caltech undergraduate students fundamental concepts in environmental chemistry, providing them with practical training and field experience in the collection, measurement, and analysis of human-induced changes on air quality, plants, soil, and water. The training program will allow undergraduates to gain a perspective on the impact of human activities on the atmosphere and biosphere.

The Alice C. Tyler Perpetual Trust was established to contribute to the improvement of the world's environment, including the preservation of all living things, the land, the waters, and the atmosphere.

Contact: Deborah Williams-Hedges (626) 395-3227

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