A team of scientists from UCLA Henry Samueli School of Engineering and Applied Science has published a finding in the journal Applied Physics Letters, explaining how they have been able to develop a semiconductor laser that works at terahertz ranges.
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Funded by the National Science Foundation, the breakthrough would help for the development of high-tech lasers usable in space exploration, law enforcement, and military interventions as well as in several mobile apps.
The terahertz frequencies can be found on the electromagnetic spectrum between microwave and infrared; and terahertz waves are good for studying semiconductors, arts, plastics, and clothing in a manner that will not damage the material under observation. It is also good for sensing and identifying chemicals, and for researching the formation of stars and the components of celestial bodies.
The UCLA group developed a vertical-external-cavity surface-emitting laser (VECSEL) – first developed by Benjamin Williams, a UCLA associate professor of electrical engineering – not adapted for terahertz ranges but which used visible light for generating strong beams.
This new VECSEL utilized a “reflectarray metasurface mirror,” composed of several tiny antenna-coupled laser cavities that reflect terahertz wave, just like a flat mirror, rather than seeing the cavities. The only thing is that the special mirror enlarges the terahertz waves in addition to reflecting them.
“This is the first time a metasurface and a laser have been combined,” Williams had said. “The VECSEL approach provides a route to have higher output powers simultaneously with excellent beam quality in the terahertz range. The metasurface approach further allows one to engineer the beam to have the desired polarization, shape and spectral properties.”
A graduate researcher, Luyao Xu, who worked in Williams’ lab noted that “By using this amplifying metasurface as part of the external cavity, not only can we improve the beam pattern, but we can also introduce new functionality to this laser with different cavity designs.
For example, by using a freestanding wire-grid polarizer, or filter, as a second mirror, we could optimize the lasers’ output power and efficiency simply by rotating the polarizer.”
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Xu is the lead author of this study, and disclosed that more scientists are trying out new designs to expand on the technology needed to advance lasers for terahertz frequencies.