CONFERENCE REVIEW

Annual IEEE/LEOS meeting celebrates the future SAN FRANSISCO, CA--The tenth annual meeting of the Lasers and Electro Optics Society (LEOS) of the Institute of Electronic Engineers (IEEE) last November was characterized by program chair Alan Willner, an associate professor at the University of Southern California (Los Angeles, CA) as "a celebration of the future." The "bullish" attitude of plenary speakers at the meeting, which conjured optical analogies to Moore`s Law of doubling chi¥capacit

CONFERENCE REVIEW

Annual IEEE/LEOS meeting celebrates the future SAN FRANSISCO, CA--The tenth annual meeting of the Lasers and Electro Optics Society (LEOS) of the Institute of Electronic Engineers (IEEE) last November was characterized by program chair Alan Willner, an associate professor at the University of Southern California (Los Angeles, CA) as "a celebration of the future." The "bullish" attitude of plenary speakers at the meeting, which conjured optical analogies to Moore`s Law of doubling chi¥capacities every couple of years, was certainly a factor in Willner`s characterization of the meeting. He noted, however, that developing the optoelectronics technology to actually meet such an explosive market demand could make for "a wild ride." But the broad scope of technological developments presented at the meeting, along with the enthusiasm of participants, indicates that the wild ride is not likely to take off with any empty seats.

Attendance at athe meeting exceeded 750 this year, and the 378 papers submitted represented an increase of 15% over the previous year. About 80% of the submitted papers were accepted. This annual increase in LEOS submissions stands in contradistinction to most conferences in the field, where the number of submissions has been decreasing, Willner said. In addition, the high percentage of invited papers--200, for a total of 516 presentations at this year`s meeting--by leaders in various fields has helped IEEE/LEOS develo¥a devoted international following, while also stimulating a high level of quality in submitted papers, Willner added.

Short wavelengths for DVDs

Submitted and invited papers in technical sessions tended to illustrate a LEOS transition during the past decade--from its roots in lasers and devices to its current focus on optoelectronics--according to conference chair Tom Koch, head of lightwave-device research at Lucent Technologies (Holmdel, NJ). For example, there has been a resurgence of innovative materials research, particularly in work with III-V materials.

In a standing-room-only postdeadline session, Shuji Nakamura an nounced the 10,000-hour blue-light-emitting laser-diode projection for Nichia Chemical Industries (see Laser Focus World, Dec. 1997, p. 9). Nakamura`s talk was followed by a presentation by researchers from Hewlett-Packard (HP; Palo Alto, CA), who, unlike other newcomers to the blue-emitting laser-diode competition, have already added a design wrinkle that they hope will hel¥them trim Nichia`s lead. The H¥researchers focused their efforts on the single-mode requirements for digital-video-disk (DVD) operation and on ease of fabrication and reported the first GaN-based ridge-waveguide laser diode with cleaved facets in their initial pulsed-operation device (see figure).

The device, grown on a sapphire substrate, included five gallium indium nitride/ gallium indium nitride (GaInN/GaInN) quantum wells, GaN guiding layers, and aluminum gallium nitride (AlGaN) cladding layers. A 5-µm-wide index-guiding ridge was formed above the to¥AlGaN cladding layer by chlorine-based reactive ion etching. The laser facets were formed by cleaving, after the sapphire had been polished as thin as 150 µm, according to Norihide Yamada, who made the presentation.

The GaInN multiple-quantum-well device emitted 200-ns pulses at 413 nm with a 1-kH¥repetition rate and a peak power of 80 mW. Threshold current was 740 mA, and the differential quantum efficiency was 8%.

New developments in long-wavelength vertical-cavity surface-emitting-laser (VCSEL) emitters for telecommunications applications were explored in the same session.

Long wavelengths for telecom

Michael Larson of Lawrence Livermore National Laboratory (Livermore, CA) reported on work that he had participated in at Hitachi (Tokyo, Japan), in which the research team succeeded in electrically pumping gallium indium nitrogen arsenide (GaInNAs) VCSELs, emitting at 1.18 µm, that were previously optically pumped.1

Researchers from the University of California at Santa Barbara described a photonic-integrated-emitter (PIE) array composed of eight pie-shaped VCSEL emitters arranged in a 60-µm-diameter circle. The multiple-wavelength PIE array was designed to be directly connected into a single multimode fiber and to allow the packaging of multiple-channel VCSEL links in the same manner as single-channel links. The focus of the researchers` efforts is to produce a VCSEL that is simple to manufacture for low-cost, short-haul, multimode wavelength division multiplexing optical data links.

Hong Choi of the Massachusetts Institute of Technology Lincoln Laboratory (Lexington, MA) described a diode laser that emits at 2.05 µm from a strained single-quantum-well (SQW) broadened-waveguide structure with a threshold current of 50 A/cm2 at room temperature. The previously reported low threshold current was 115 A/cm2 for a similar gallium indium arsenic antimonide/aluminum gallium arsenic antimonide (GaInAsSb/AlGaAsSb) device.2 The improvement may be due to an increased gain coefficient in the SQW caused by improved interface quality and increased strain, Choi said.

Choi`s grou¥estimated the SQW strain value in its device at 1.4%. Graded regions were also included in the device structure to reduce series resistance, and "the epitaxial surface was mirror smooth with no evidence of crosshatch," said Choi.

Moving beyond basic research, other topics of interest at the meeting included low-cost module-packaging technology based on silicon mother boards, the use of lasers in robotized assembly techniques, and the problem of actually getting the bandwidth provided by optics to the deskto¥in a market that is still dominated by copper wiring.

The broad focus of the meeting, from cutting-edge research to practical applications, as well as marketing, is another indication of its evolution over the past decade, Kohn said. "This [meeting] has become the home for optoelectronics, from the science to the customer," he said.

Hassaun Jones-Bey

REFERENCES

1. M. C. Larson et al., Electron. Lett. 33(11), 959 (1997).

2. D. Z. Garbuzov et al., Appl. Phys. Lett. 69, 2005 (1996).

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