Stanford, CA--On the heels of the 2010 50th anniversary of the laser, the year 2011 marks the 50th anniversary of nonlinear optics. The OSA Nonlinear Optics (NLO) topical meeting held this summer in Kauai, HI included a symposium celebrating 50 years of nonlinear optics, and the University of Michigan will host "The Birth of Nonlinear Optics 50th Anniversary Symposium" at their Ann Arbor, MI campus on October 24, 2011. In 1961, the University of Michigan's Peter Franken, Alan Hill, Wilbur Peters, and Gabriel Weinreich in the Randall Laboratory observed the first generation of optical harmonics and published their findings in Physical Review Letters.
The Stanford Photonics Research Center (SPRC) 2011 Annual Symposium, held September 12-14 on the campus of Stanford University (Stanford, CA), highlighted nonlinear optics in three Wednesday morning presentations in its "Nonlinear Optics--History and Future" session; however, you could say that the concepts of nonlinear optics were woven throughout the three-day SPRC Symposium presentations. The very ability to use harmonic generation, optical parametric oscillation, difference frequency generation, self-phase modulation, four-wave mixing, multiphoton absorption, and other nonlinear effects is fundamental to photonics research and development today.
The Stanford nonlinear connection
Nonlinear optics has been paramount to the many photonic achievements at Stanford University and numerous other photonics institutions; in fact, the SPRC Symposium was formerly titled CNOM, the annual Stanford Center for Nonlinear Optical Materials meeting.
After the initial Wednesday morning presentation in which LLNL physicist Chris Ebbers described the National Ignition Facility (NIF) and the interesting history of the nonlinear potassium diphosphate (KDP) crystals that NIF critically depends upon, Stanford professor and SPRC co-director Robert L. (Bob) Byer presented "50 years of Nonlinear Optics; a Stanford Perspective." In his presentation, Byer went through the timeline of nonlinear optics at Stanford, describing some of the events surrounding the demonstration of the first tunable CW parametric laser via optical parametric oscillation (OPO) by Stanford University's Bob Byer and Stephen E. Harris in 1968. On the way to creating a functioning OPO, it seems that the first 1 cubic centimeter lithium niobate (LiNbO3) crystal obtained by Stanford from Bell Labs was dropped, delaying the project. However, Stanford found a resource to grow LiNbO3 and other nonlinear crystals; today, nonlinear materials are being used for research in atmospheric sensing, for NIF, and even in accelerator and X-ray projects, not to mention their tremendous utility in laser research for frequency generation and other effects. Byer brought up the irony that green laser pointers—a poster child of nonlinear optics—were given a 20 year patent in 1986 that, unfortunately for their inventors, expired just shortly before green laser pointers were commercially released.
A modern, emerging manifestation of the power of nonlinear optics is quantum computing. In the final Wednesday morning Nonlinear Optics session, Stanford University postdoctoral fellow Sharon Shwartz explained how polarization-entangled photons at X-ray energies can be generated using another nonlinear effect, parametric down-conversion (PDC) in diamond.
Other SPRC highlights
Besides the nonlinear optics presentations, the SPRC 2011 Annual Symposium highlighted how a myriad of photonics research achievements are directly translating to real-world applications.
The symposium plenary talk on "Nonlinear Optics at the Timescale of the Electron" from Margaret Murnane, JILA fellow and physics faculty at the University of Colorado, truly described nonlinear optics at the extreme: the generation of bright, coherent, attosecond-scale X-ray supercontinua at 1.6 keV that can be used to probe light-matter interactions like never before. For example, Murnane explained that at the moment, there is no microscopic model to explain how magnets work. Ongoing research in attosecond spectroscopy and attosecond X-ray generation may be close to finding the answer.
In his talk "Applications of Integrated Quantum Photonics to Novel High-Performance Computing," HP Laboratories fellow Ray Beausoleil explained how HP is trying to overcome the "curse" of Moore's Law—the market expectation that computer performance will scale exponentially forever. He explains how CMOS alone cannot overcome the tremendous power consumption of today's chip-based computational and information systems. Through the DARPA MesoDynamic Architectures or Meso program, HP is attempting to shift discussion of quantum computing away from entanglement and towards "quantum control of coherence" using the nonlinear optical Kerr effect. Beausoleil emphasized that his group is not trying to build an optical computer, but it does want to use integrated photonic structures to show how coherence could be used as a future computational scheme.
Alan Horsager of the Horsager Lab at USC and co-founder and chief science officer of Eos Neuroscience discussed optogenetics, an emerging field of study that uses light-sensitive molecules to trigger or suppress neural function. The principal focus of many optogenetics researchers is restoring sight to the blind; unfortunately, human trials that could actually confirm just what level of vision a person using these therapies might experience are years in the future.
Also in the world of biooptics, non-ophthalmic optical coherence tomography (OCT) has left the laboratory and is taking a foothold in clinical settings. I was amazed to see how OCT image resolution has improved over the past few years and awed by the presentation given by Guillermo Tearney, professor of pathology at Harvard Medical School, who transported the audience inside the human body through detailed images and videos. Endoscopic OCT systems can now image not only the colon and stomach, but are also being used for full coronary imaging thanks to frequency domain OCT (FD-OCT).
Monday's evening banquet was a good time to dine with photonics colleagues as well as Stanford students. These young people are very smart and renewed my hopes for a future that can be improved through education and technology (if they can continue to pay for schooling). After a great meal and a birthday celebration for Stanford's esteemed McMurtry professor of engineering Anthony E. Siegman, Robert J. Lang gave a presentation on the link between photonics and origami (which I described in my latest Laser Focus World PHOTON FOCUS blog at http://www.laserfocusworld.com/blogs/photon-focus/2011/09/origami-and-photonics-fold-together.html). If you can make it to next year’s SPRC Annual Symposium, please go; you won't be disappointed!