CLEO/IQEC 2004 heralds novel technology and exciting applications

April 1, 2004
Technical sessions will reveal what is ahead in the areas of semiconductor emitters, displays, nonlinear and ultrafast optics, sensing, and biological applications.

This year's Conference on Lasers and Electro-Optics and the International Quantum Electronics Conference (CLEO/IQEC; May 16–21; San Francisco, CA) will include thousands of technical papers, a distinguished list of invited speakers, and many short courses, as well as exhibits. CLEO/IQEC is sponsored by American Physical Society/Division of Laser Science, IEEE/LEOS, and the Optical Society of America. This year, the Photonic Applications, Systems and Technologies (PhAST) Conference will debut, collocated with CLEO/IQEC (see "PhAST conference debuts with one-on-one time for engineers").

Two joint CLEO/IQEC 2004 symposia cover energetic ultrafast laser-driven radiation sources and nonlinear photonics in optical lattices. IQEC will hold two symposia on spin photonics and single-photon sources, detectors, and applications.

Medical and biological applications

Chair Sergio Fantini of Tufts University (Medford, MA) says that many papers in the six Medical and Biological Applications sessions focus on optical coherence tomography (OCT). Such technology is already a clinical device for eye-related imaging, he says, but many groups are working on making it compatible with endoscopy and producing video-rate images.

A notable paper in the OCT area comes from researchers at the University of California–Los Angeles (Los Angeles, CA) and James Fujimoto's group at the Massachusetts Institute of Technology (MIT; Cambridge. MA), "Two-dimensional endoscopic MEMS [microelectromechanical systems] scanner for high-resolution optical coherence tomography." The researchers use a novel two-dimensional scanner using comb-drive actuation and demonstrate imaging at up to 20 frames/s with about 5-µm axial resolution.

In a different area, Manoj M. Varma and others from Purdue (West Lafayette, IN) will present a paper, "The BioCD: A high-sensitivity spinning-disk interferometer for antigen detection," which describes using a spinning-disk interferometer to perform fast immunoassays with sensitivity to 100 ng/ml and a detection limit approaching 100 attomoles per track. "The idea," says Fantini, " is to use the technology of music CDs as a base." The BioCD technology is described further in a paper as part of the Holography, Wavemixing, Photorefractives & Storage program.

Active optical sensing

In a related area, the sessions on active sensing include many papers on terahertz sensing, a technology that chair John Zayhowski of MIT Lincoln Laboratory (Lexington, MA), says "is coming of age." Sensing at terahertz frequencies can penetrate materials that are opaque in other areas of the spectrum (and vice versa, Zayhowski points out, "anything wet won't work"). The ability to do vibrational spectroscopy through containers is attractive to the U.S. government, which is very concerned about the ability to detect chemicals. This interest and the funding that goes with it drive current research.

Among the highlight papers in this session is one by Yuichi Ogawa and others at RIKEN (Wako, Saitama, Japan) that uses terahertz imaging to detect and identify drugs concealed in envelopes. In another, a collaboration between Osaka University and the Osaka Police, Kohji Yamamoto and others considered how terahertz spectroscopy could be applied to detecting mail bombs. Nearly all mail bombs use the same explosive: C-4. They demonstrate that C-4 shows characteristic signatures in five terahertz bands.

Ultrafast optics, optoelectronics, applications

Chair Franz Kaertner of MIT says that the use of fiber lasers continues to be a popular subject in the Ultrafast Optics, Optoelectronics, and Applications sessions.

In an invited paper, Victor Bespalov and a number of other researchers from the Institute of Applied Physics, Russian Academy of Science (Novgorod, Russia) and the Russian Federal Nuclear Center (Sarov, Russia) describe a parametric chirped pulse amplifier based on potassium dihydrogen phosphate crystals that created 100-mJ 30-fs pulses at 910 nm. The researchers believe that by adding two more parametric amplifiers, the system could be scaled up to provide joule or multijoule pulses.

A chirped-pulse amplifier constructed using optical fiber and including an air-guiding photonic-bandgap-fiber compressor will be presented by Jens Limpert and others from the University of Jena (Jena, Germany). The use of fiber, explains Kaertner, gives this system the potential to be an inexpensive and robust source of ultrafast high-power pulses. The peak power out of the compressor fiber is as high as 820 kW (see Fig. 1).

Solid-state lasers

Kunio Yoshida of Osaka Institute of Technology (Osaka, Japan) and others will give an invited talk on creating a multilayered Nd:YAG laser without growing the material in a single-crystal boule. In the device, a layer of Nd:YAG between undoped YAG is created using ceramic technology. In a metal mold, three layers of powder are pressed individually, then all together, then sintered in vacuum. The result is an optical-grade polycrystalline material. The ceramic technology could possibly offer lower-cost materials in complex structures.

Chair Markus Pollnau of the Swiss Federal Institute of Technology (Lausanne, Switzerland) says yttrium and gadolinium vanadate lasers, and modelocked lasers are the most popular paper subjects this year. The bounce-oscillator design is attracting interest, especially when it results in record-high powers from gadolinium vanadate as reported by Ben Thompson and others at Imperial College (London, England).

Displays and solid-state-lighting devices

Displays and solid-state lighting represent a new area of coverage for CLEO. Chair Fred Schubert of Rensselaer Polytechnic Institute (Troy, NY) explains that significant changes in the field of displays are bringing new products to market. "According to the information that I have," says Schubert, "2004 is the first year that fewer cathode-ray tubes will be sold than flat-panel displays" for applications that can use either. Liquid-crystal displays backlit with light-emitting diodes (LED), plasma displays, active-matrix LCDs, and OLEDs (organic LEDs) are all active areas of research.

Light-emitting diodes and OLEDs being developed for solid-state lighting offer benefits of saving energy and reducing the environmental contamination caused by mercury (included in many fluorescent lights). "This is an absolutely fascinating field," says Schubert. Because OLEDs can be modulated and wavelength tuned, they offer new functionalities for lighting applications including sensing, communications, and biotechnology.

The papers on solid-state lighting mostly focus on light extraction and internal efficiency. Efficiencies for these devices typically range from 10% to 50%, depending on the materials involved. For example, Lu Chen at Brown University (Providence, RI) and others have increased output by eight times by incorporating a photonic crystal in their nitride LED.

Semiconductor lasers and LEDs

More than 20% of the papers in the Semiconductor Lasers and LEDs program focus on vertical-cavity surface-emitting lasers (VCSELs), reports Chair Joseph Abeles of the Sarnoff Corporation (Princeton, NJ). Invited speaker Claire Gmachl of Princeton University (Princeton, NJ) discusses quantum-cascade devices as both lasers and nonlinear crystals. Gmachl explains, "The optical nonlinearity is based on electronic intersubband transitions in quantum wells." Just as the output wavelength of quantum-cascade lasers can be manipulated during the design process by choosing the layer thicknesses, so can the nonlinearity be part of the design. Last year, the researchers demonstrated the existence of nonlinear effects; now they are making rapid progress in improving conversion efficiencies. "We are reaching a few hundreds of microwatts of power," reports Gmachl, "and we are confident that we can improve this by another couple of orders of magnitude."

Applications of nonlinear optics

Another material takes on nonlinear properties in a paper from the Applications of Nonlinear Optics sessions. Konstantin Vodopyanov and others in Marty Fejer's group at Stanford University (Palo Alto, CA) and Thales Research and Technology (Orsay, France) describe creating the first optical parametric oscillator based on gallium arsenide (see Fig. 2). They created a room-temperature mid-IR source that can be tuned from 2 to 10 µm. Because this covers the "fingerprint region" of many common molecules, and because the small device can be pumped by a miniature laser, it offers the potential for a compact, tunable IR device that could be used for spectroscopy and biomedical applications.

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About the Author

Yvonne Carts-Powell | Freelance Writer

Yvonne Carts-Powell is a freelance writer living in Belmont, MA.

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