Researchers Achieve 40% Enhanced Terahertz Photoresponse Using Graphene Cavities

Scientists are increasingly focused on harnessing terahertz (THz) radiation for next-generation technologies, but efficient detection remains a significant challenge. Domenico De Fazio (Ca’ Foscari University of Venice), Sebastián Castilla and Karuppasamy P. Soundarapandian (both ICFO-Institut de Ciencies Fotoniques) et al. have now demonstrated a substantial enhancement of the THz photoresponse using a novel acoustic plasmon cavity design in scalable graphene, achieving confinement factors of up to 4000. Their research, detailing a device where antenna coupling efficiently launches acoustic graphene plasmons, reveals pronounced peaks in photovoltage and a modulation of up to 40% between 6 and 90 K, attributable to Fabry-Pérot cavity resonances, a breakthrough that paves the way for low-power, scalable THz detection platforms.

Soundarapandian (both ICFO-Institut de Ciencies Fotoniques) et al. have now demonstrated a substantial enhancement of the THz photoresponse using a novel acoustic plasmon cavity design in scalable Graphene, achieving confinement factors of up to 4000.

Graphene acoustic plasmons enhance terahertz detection

The research team successfully fabricated an antenna-coupled device utilising chemical vapour deposited (CVD) Monolayer graphene to manipulate and concentrate THz fields at the nanoscale. The team achieved precise control over the AGPs by simultaneously employing the dipole antenna lobes as gate electrodes, concentrating the incoming THz radiation and efficiently launching these plasmons. This exceptional confinement dramatically enhances light-matter interaction, paving the way for more sensitive and efficient THz detectors. These findings are particularly important as THz technology finds increasing applications in diverse fields, including photonics, quantum technologies, wireless communications, and sensing, demanding more efficient and compact detection systems. Experiments show that this novel design overcomes limitations of previous graphene-based detectors, which often required cryogenic operation or exhibited weak resonance features. The ability to achieve such strong field confinement and efficient energy conversion promises to unlock new possibilities in THz imaging, spectroscopy, and communication systems, potentially revolutionising these fields with more sensitive and energy-efficient devices.

Graphene Split-Gate Antenna Fabrication and Characterisation are presented

Scientists engineered a novel terahertz (THz) photoresponse device leveraging polaritonic cavity enhancement within an antenna-coupled graphene monolayer. Researchers fabricated the device using chemical vapor deposited (CVD) monolayer graphene transferred onto a highly resistive silicon substrate with a 300nm silicon dioxide layer. The graphene channel, measuring 2μm in length and width, was patterned into an H-shape via reactive ion etching to minimise contact resistance with metallic electrodes. A 40nm aluminum oxide layer, deposited by atomic layer deposition, served as the gate dielectric, crucial for electrostatic control of the graphene.

The study pioneered a split-gate architecture where electrodes functioned as a dipole antenna, resonantly coupled to 1.83 to 2.52THz radiation. Full-wave electromagnetic simulations, detailed in the supplementary material, optimised the antenna length at 40μm and a 200nm gap between lobes, balancing resolution limits with leakage prevention. This configuration efficiently converts incident THz radiation into a localised electric field, exciting AGP modes within the graphene channel. Experiments employed cryogenic cooling, reducing temperatures down to 5K, to observe pronounced resonances modulating the photovoltage response.

Scientists observed Fabry, Pérot-type resonances forming both across the full graphene channel and localised beneath individual gate electrodes. This method achieves a 30% higher plasmonically enhanced photoresponse compared to conventional PTE responses, aligning Fermi energy with the peak of the Seebeck coefficient to maximise the effect. The work establishes that coherent AGP resonances can be sustained in CVD graphene under appropriate gating conditions and device architecture.

Graphene Cavity Enhances Terahertz Photoresponse by 40%, demonstrating

Experiments revealed that the dipole antenna lobes simultaneously function as gate electrodes, concentrating the incident THz field and efficiently launching AGPs, which subsequently drive a strong PTE signal. The research team measured a significant enhancement in field confinement, with lateral and vertical factors of 165 and 4000 respectively, demonstrating the ability to squeeze THz waves into extremely small volumes. Scientists recorded that the observed resonances are not merely a consequence of device geometry but are actively tuned by the applied gate voltage, allowing for dynamic control of the THz response. The breakthrough delivers a significant step forward in THz technology, offering a potential solution for applications requiring sensitive and efficient detection of these frequencies, such as biomedical imaging, security screening, and high-speed wireless communications. This work establishes a foundation for developing compact, low-power THz detectors with tailored spectral responses.