CONFERENCE REVIEW

KAUAI, HI--The Nonlinear Optics `98 Topical Meeting, jointly sponsored by IEEE, LEOS, and OSA, convened here at the Princeville Hotel, Aug. 9-14. The symposium attracted 196 scientists--including three Nobel prize winners--and was as much a celebration of past success as a showcase of recent results and a venue for discussion. Wayne Knox, program cochair and head of advanced photonics research at Lucent Technologies--Bell Labs (Murray Hill, NJ), described the agenda as "creating a Gordon Confere

CONFERENCE REVIEW

Communications progress reported at nonlinear-optics meeting

Marc D. Levenson

KAUAI, HI--The Nonlinear Optics `98 Topical Meeting, jointly sponsored by IEEE, LEOS, and OSA, convened here at the Princeville Hotel, Aug. 9-14. The symposium attracted 196 scientists--including three Nobel prize winners--and was as much a celebration of past success as a showcase of recent results and a venue for discussion. Wayne Knox, program cochair and head of advanced photonics research at Lucent Technologies--Bell Labs (Murray Hill, NJ), described the agenda as "creating a Gordon Conference atmosphere, with its risks and controversies, at a pleasant Hawaiian location."

There were few controversies, and most of them concerned semantic issues, such as whether "spatial soliton" was just another name for "self-focusing," or whether fast-pulse measurements should be described in terms of steady-state nonlinearities. Many presentations described practical realizations of old dreams. Nicolaas Bloembergen of Harvard University (Cambridge, MA), for example, reviewed the progress in measuring short time intervals from the 17th century (1 s) through the first use of the Kerr shutter 100 years ago (10 ns) to today`s 6-fs experiments, some of which were reported in other sessions. Robert Byer of Stanford University (Palo Alto, CA) described the progress of engineered nonlinear materials for frequency generation, beginning with Bloembergen`s 1968 patent of quasi-phase-matching through this year`s introduction of the first commercial device.

No field reported more progress than optical communications, where optical nonlinearities combine with chromatic dispersion and amplified spontaneous emission to limit the performance of leading-edge systems. "The task of overcoming the nonlinearities will produce gainful employment for system engineers indefinitely," predicted Andrew Chraplyvy, department head of Lightwave Systems Research at Bell Labs.

Chraplyvy pointed out that many nonlinearities are misunderstood and need not noticeably impact transmission. Other deleterious effects can be fixed with dispersion control or data coding. Still, with fibers now capable of 150 wavelength channels and soliton transmission on the horizon, even weak nonlinear effects can reduce signal margins. "Each decibel of improvement is worth $250 million in a transoceanic system," he reported.

Knox observed that some essential communications components, such as a 1000 ¥ 1000 crossbar switch, still require innovations. Allan Snyder of the Research School of the Australian National University (Canberra) shared a vision of light guiding through spatial soliton interactions as a way to perform the required processing. While there is a long way to go, the basic phenomena of splitting, fusing, and redirecting beams have been documented.

Two invited papers, presented by Lambertus Hesselink of Stanford and Karsten Buse of the University of Onsnabrück, Germany, reported on the status of holographic optical data storage, which has dominated previous conferences. The best material remains a doped version of lithium niobate, despite much research on other materials. The optimal dopant recipe, however, may not simply be iron, but could include manganese and/or cerium. L. N. Durvasula of the US Defense Advanced Research Projects Agency (Washington, DC) observed that, while photorefractive data storage is not yet a killer application for nonlinear optics, "it is killing the sponsor!"

A panel discussion on "successfully applied" nonlinear effects produced few commercial examples. Herwig Kogelnik of Bell Labs observed that success in many optics applications, such as fiber communications and high-power lasers, required an understanding of nonlinear phenomena. He cited the fiber-Raman frequency-shifting amplifier and the phase-conjugate reflector as examples of useful nonlinear components. Erich Spit¥of Thomson (Paris, France) recounted the many harmonic-generation and laser frequency-conversion applications. Quasi-phase-matched materials will make all-solid-state tunable parametric oscillators commercially viable, according to Spitz. Such sources would be useful in spectroscopy and environmental monitoring.

Other oral and poster papers covered topics in nonlinear materials--emphasizing semiconductors, organics, and metals--fundamental physics, including quantum optics and cavity electrodynamics, and terahert¥radiation. The most fascinating phenomenon for many staying in the Princeville Hotel, however, was the unique shower window, which became translucent at the flip of a switch, blocking the view of the stormy coastline. Galina Khitrova and Wayne Knox, the program cochairs, proposed a contest to determine the mechanism, which stimulated a frenzy of experiments with laser pointers, cameras, and other available apparatus. First prize went to Gary Cook of the Defence Evaluation and Research Agency (Malvern, England) and James Ho of TRW (Redondo Beach, CA) for their persuasive demonstration of Rayleigh scattering by small-index inhomogeneities. Art Ashkin of Bell Labs obtained a similar result using less-modern methods.

The Nonlinear Optics `98 Topical Meeting reflected the current interests of scientists and institutions in the field. Notably absent were representatives of laser fusion and Star Wars, as well as the optical-data-storage industry. New areas related to nonlinear optics included tailoring atomic-wave functions, quantum communication, and multiphoton microscopy. Thus, intellectual vitality of the nonlinear optics field continues although dramatically successful applications remain in the future.

MARC D. LEVENSON is editor in chief of Microlithography World magazine and proprietor of M. D. Levenson Consulting, 19868 Bonnie Ridge Way, Saratoga, CA 95070; e-mail: microlith@aol.com.

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