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Topological fiber lasers: a breakthrough
A team of researchers from Singapore designed the first electrically driven topological laser system. This fiber laser efficiently overcomes manufacturing imperfections due to the application of topologically protected photonic modes. In the 1980s, the researchers discovered that electrons flowing in certain materials had “topological” qualities; therefore, installed in fiber laser systems, they allowed electrons to flow around corners or defects without scattering or leaking.
This topological technique has been recently applied to photons by a team of researchers from Singapore. They used a quantum cascade fiber laser on advanced semiconductor wafers developed by the team. The team exploited a design that included a valley photonic crystal to reach topological states on a laser beam platform.
Design of the compact fiber laser system
The design of the compact fiber laser system contains “hexagonal holes arranged in a triangular lattice, etched into a semiconductor wafer. Within the microstructure, the topological states of light circulate within a triangular loop with a 1.2-mm circumference. The loop acts as an optical resonator to accumulate the light energy required to form a laser beam.” The laser beam travels in this loop and navigates the sharp angles of the triangle because of certain characteristics of topological states, whereas normal lightwaves are disrupted by the sharp angles, preventing them from circulating smoothly.
Electrically pumped THz quantum cascade fiber lasers
The quantum cascade fiber laser allows emitting a laser beam at terahertz (THz) frequencies. Although previous demonstrations needed an external laser beam source for optical pumping, now the developed fiber laser is based on an electrically pumped THz quantum cascade technology that uses topologically protected valley edge states; thus, the application includes the valley degree of freedom in photonic crystals. Electrically driven semiconductor laser systems are considered to be the most standard type of laser technology device at present and have a wide range of applications, from barcode readers to laser ranging sensors for autonomous vehicles.
The manufacture of fiber laser systems has numerous challenges, and modern laser module designs may not work well if any imperfections are introduced into the structure of the laser during manufacturing. The innovative topological laser system addresses the issue and may lead to more effective production using current laser technologies.