In the rapidly evolving field of terahertz technology, flexibility has become a key requirement for next-generation wearable photonics and intelligent communication systems. However, mechanical deformation often leads to performance degradation, causing information loss or signal interruption. Addressing this challenge, a collaborative research team led by Professor Qingli Zhou from Capital Normal University and Professor Chen Ge from the Institute of Physics, Chinese Academy of Sciences, has developed flexible tellurium (Te) nanofilms on polyethylene terephthalate (PET) substrates that serve as ultrafast all-optical terahertz modulators with exceptional mechanical robustness.
The new devices, detailed in a paper published in Light: Advanced Manufacturing, leverage the unique helical chain structure of tellurium, which provides good optical response, high carrier mobility, and ambient stability. When integrated with flexible PET substrates, the Te nanofilms form mechanically robust and optically active films suitable for terahertz modulation. The modulators exhibit a high modulation depth of 50% on the picosecond timescale, along with low insertion loss and broadband operation. Moreover, they demonstrate an ultrasensitive response under low pump excitation, making them highly efficient for practical applications.
One of the most critical aspects of flexible devices is their ability to maintain performance under mechanical stress. The researchers rigorously tested the Te/PET films under various bending conditions, including repeated bending cycles and small bending radii. Remarkably, the transient terahertz photoresponse remained nearly unchanged, indicating that the device's mechanical tolerance is sufficient to preserve reliable terahertz modulation during deformation. This stability is attributed to the inherent flexibility of the PET substrate and the mechanical resilience of the Te nanofilms.
To explore the information-processing potential of the device, the team integrated the measured terahertz modulation response into an artificial neural network (ANN) for image recognition tasks. The recognition accuracy remained stable under different bending conditions, demonstrating that the mechanical robustness of the Te/PET device translates directly into reliable information processing. This finding suggests that flexible terahertz modulators could serve as front-end functional units for intelligent sensing and neuromorphic optoelectronic systems.
The scientists summarized their work, stating, "We introduce flexible Te/PET films as a mechanically robust platform for ultrafast all-optical terahertz modulation. The device exhibits broadband response, low insertion loss, high modulation efficiency, and picosecond photoresponse, while maintaining stable performance under bending deformation." They further added, "The stable terahertz response under different mechanical states enables reliable neural-network-based image recognition, suggesting the potential of Te-based flexible terahertz devices for intelligent sensing and wearable optoelectronic systems." The team forecasts that these results provide a new device strategy for flexible terahertz modulators and offer guidance for developing mechanically robust terahertz optoelectronic devices that can operate in complex deformation environments.
This research was supported by several funding sources, including the National Key R&D Program of China, the Postdoctoral Fellowship Program of CPSF, and the Beijing Natural Science Foundation, among others. The work represents a significant step toward the practical implementation of flexible terahertz technology in intelligent communication and sensing applications.
