Flexible Te/PET Films Enable Robust Ultrafast All-Optical Terahertz Modulators

Flexible terahertz devices are essential for the advancement of wearable photonics, intelligent communication, and flexible imaging systems. However, practical applications often subject these devices to mechanical deformation, which can lead to structural changes, information loss, or signal interruption. The development of terahertz modulators that maintain high performance under such conditions remains a critical challenge.

In a new publication in Light: Advanced Manufacturing, a 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 introduced flexible tellurium (Te) nanofilms grown on polyethylene terephthalate (PET) substrates as all-optical terahertz modulators. These devices exhibit high modulation efficiency, picosecond response, low insertion loss, and robust bending tolerance. The Te/PET films leverage the unique helical chain structure of tellurium, its good optical response, high carrier mobility, and ambient stability, making them a promising material platform for flexible terahertz applications.

The team's device achieved a modulation depth of 50% on the picosecond timescale with a broadband response and low insertion loss, even under low pump excitation. This performance highlights the potential of Te/PET films for developing flexible terahertz functional devices. The researchers also tested the mechanical stability of the device under various bending conditions. The transient terahertz photoresponse remained nearly unchanged after repeated bending cycles and under a small bending radius, demonstrating the mechanical tolerance of the Te nanofilms and the flexibility of the PET substrate.

To explore the information-processing capability of the device, the team integrated the measured terahertz modulation response into an artificial neural network (ANN) for image recognition. The recognition accuracy remained stable under different bending conditions, indicating that the mechanical robustness of the Te/PET device translates into reliable information processing. This suggests that flexible terahertz modulators could serve as front-end functional units for intelligent sensing and neuromorphic optoelectronic systems.

The scientists summarize their work: "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 add, "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 results provide a new device strategy for flexible terahertz modulators and offer guidance for the development of mechanically robust terahertz optoelectronic devices operating in complex deformation environments. This research was supported by various funding agencies, including the National Key R&D Program of China and the National Natural Science Foundation of China.