THz technology has attracted increasing attention due to its unique spectral position and physical properties. With promising applications in communications, material characterization, security screening, and biomedicine, terahertz waves are widely regarded as a critical bridge between electronics and photonics. However, practical deployment of THz systems remains challenging because of severe transmission losses and the scarcity of efficient functional devices in this frequency range. Developing effective and stable solutions for terahertz wave transmission is therefore one of the central challenges in advancing THz technology.
In a new paper published in Light: Science & Applications , a team of scientists, led by Professor Longqing Cong from Southern University of Science and Technology, China, and co-workers have proposed a novel approach by introducing a topological DVM into THz photonic crystal fibers. This work experimentally realizes a SPSM THz fiber featuring an ultra-broad bandwidth and zero polarization dispersion. Using time-resolved THz scanning near-field microscopic spectroscopy, the team successfully observed and verified the topological fiber mode. This design strategy provides a promising solution for efficient, stable, and crosstalk-free terahertz signal transmission, with potential applications in terahertz sensing, subwavelength-resolution imaging, and distributed quantum networks.
In this work, the authors introduce the topological DVM, which originally rooted in the Jackiw–Rossi zero-energy modes of condensed matter physics, into THz photonic crystal fibers. Spectrally, the DVM resides in the middle of a topological vortex bandgap, while spatially it is strongly localized at the center of the structure. By introducing an out-of-plane wavevector, the DVM is transformed into a guided mode in the photonic crystal fiber. These scientists summarize the advantages of their fiber in theory:
“This non-degenerate mode inherently supports pure SPSM transmission without polarization dispersion. Furthermore, due to its topological origin, the DVM enables ultra-broadband SPSM transmission within the topological bandgap, while remaining free from in-plane radiation losses.”
“To validate the proposed concept, we fabricated the fiber using 3D printing technology. In experiment, both the band structure of the DVM and its near-field mode profiles were characterized using a home-made THz near-field time-domain scanning spectroscopy system. By applying short-time Fourier transform analysis to the time-domain data yields the temporal-spectral-spatial mapping characteristics of the DVM” they added.
“At a fundamental level, the results extend the scope of topological photonics into fiber-based systems. From an application perspective, we establish a key device platform for THz integrated systems. With continued advances in low-loss materials and high-precision fabrication technologies, DVM-based THz photonic crystal fibers hold strong promise for practical long-distance THz transmission.” the scientists forecast.
Light Science & Applications
Experimental observation of topological Dirac vortex mode in terahertz photonic crystal fibers