A New Breakthrough in Ultrashort Laser Pulse Technology

Lasers are becoming an integral part of countless devices and industries. When a laser beam interacts with the surface of a nanoscale material, it emits a wave of light called a "plasmon" (plasma exciton), and the properties of a given plasma exciton can convey information. In optical transmission, a laser pumps light into a component called a "saturable absorber" to produce an optical signal.
Recently, Yu Yao, associate professor of electrical engineering at Arizona State University, and her research team at Arizona State's Center for Photonics Innovation have designed a faster, more energy-efficient nanoscale laser element called a graphene-plasma hybrid meta-structured saturable absorber, or GPSMA.
GPSMA has potential applications in industries such as communications, information processing, spectroscopy and biomedicine. The absorber can be used to improve speed, efficiency, and overall performance to advance data transmission, information processing, biomedical sensing, and imaging technologies.
Because of its beneficial properties in optical modulation and saturable absorption, Yu Yao's team incorporated an artificially engineered metal-graphene hybrid in their development.
In a recent paper published in the scientific journal ACS Nano, Yao details how her lab integrated a graphene-based saturable absorber and how they managed to improve the device to reduce power consumption while maintaining ultra-fast response times.
They obtained these important results by designing an optical antenna array that focuses light onto nanoscale gaps in the material, known as hot spots, to promote absorption. By focusing the laser on these hot spots, they observed improved performance and reduced energy consumption.
"Graphene is lightweight and has fast optical response times, but low absorption in its monolayer form," said Yu Yao, "We designed the device so that light absorption at nanoscale hotspots can be increased by more than three orders of magnitude, producing not only strong light absorption but also saturation absorption effect. With GPSMA, we are making a saturable absorption device that can actually reduce power consumption by nearly two to three orders of magnitude."
Based on its significantly increased speed, their new technology will open up new opportunities for infrared laser spectroscopy and high-speed optical signal communications (fiber optic cable andcommunications).
"Our device can operate at record high speeds," said Yu Yao, "Conventional saturable absorbers can operate on a nanosecond time scale, but now we can reach about 60 femtoseconds, more than 100,000 times faster than before."
GPSMA currently operates at near-infrared wavelengths on the electromagnetic spectrum. Because graphene has a broad optical response, it can extend its spectral coverage to longer wavelengths in the infrared spectral region, which has important implications for molecular spectroscopy and optical communications. However, for longer wavelengths, it is traditionally more difficult to achieve saturable absorption and generate ultrashort laser pulses. Therefore, the GPSMA design concept can fill such a technological gap.
Yu Yao's team's device has potential applications in the telecommunications, energy and biomedical industries. Such absorbers could be used to improve the speed, efficiency and overall performance of fiber optic cables, opening up opportunities for advancing data transmission, solar cell performance and disease detection imaging technologies.