Flexible terahertz devices are critical for emerging applications in wearable photonics, intelligent communication, and flexible imaging. However, mechanical bending often degrades performance, causing signal loss. A new study introduces tellurium (Te) nanofilms on polyethylene terephthalate (PET) substrates as a solution, achieving ultrafast all-optical terahertz modulation with high efficiency and robustness.
Published in Light: Advanced Manufacturing, the research led by Professor Qingli Zhou from Capital Normal University and Professor Chen Ge from the Institute of Physics, Chinese Academy of Sciences, demonstrates that Te/PET films can serve as flexible terahertz modulators. The device exhibits a modulation depth of 50% on a picosecond timescale, low insertion loss, and broadband operation, all while maintaining performance under bending. This is attributed to Te's unique helical chain structure, high carrier mobility, and ambient stability, combined with the flexibility of PET.
The team tested mechanical stability by subjecting the device to repeated bending cycles and small bending radii. The transient terahertz photoresponse remained nearly unchanged, indicating excellent tolerance to deformation. This robustness stems from the mechanical resilience of Te nanofilms and the flexibility of the PET substrate, ensuring reliable modulation even under stress.
To assess practical utility, the researchers integrated the measured terahertz response into an artificial neural network (ANN) for image recognition. The recognition accuracy stayed consistent under various bending conditions, demonstrating that the device's mechanical stability translates into reliable information processing. This suggests potential for flexible modulators as front-end units in intelligent sensing and neuromorphic optoelectronic systems.
“We introduce flexible Te/PET films as a mechanically robust platform for ultrafast all-optical terahertz modulation,” said the scientists. “The device exhibits broadband response, low insertion loss, high modulation efficiency, and picosecond photoresponse, while maintaining stable performance under bending deformation.” They added that the stable response enables reliable neural-network-based image recognition, highlighting potential for wearable optoelectronic systems.
The findings offer a new device strategy for flexible terahertz modulators, providing guidance for developing mechanically robust terahertz optoelectronics capable of operating in complex deformation environments. The study was supported by multiple Chinese funding agencies, including the National Key R&D Program and the National Natural Science Foundation of China.
