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Updated: Sep 13, 2025
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Fabrication of Gate-tunable Graphene Devices for Scanning Tunneling Microscopy Studies with Coulomb Impurities
Published on: July 24, 2015
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Achieving 100% amplitude modulation depth in the terahertz range with graphene-based tuneable capacitance
Ruqiao Xia1, Nikita W Almond2, Wadood Tadbier3
1Cavendish Laboratory, University of Cambridge, Cambridge, UK. rx224@cam.ac.uk.
Light, Science & Applications
|August 3, 2025
Summary
Researchers developed new terahertz modulators using graphene capacitors in metamaterials. This capacitive tuning achieves over four orders of magnitude modulation depth, significantly improving terahertz radiation control.
Area of Science:
- Terahertz (THz) science and technology
- Metamaterial applications
- Optoelectronics
Background:
- Effective control of terahertz radiation necessitates fast, efficient modulators with large modulation depth.
- Metamaterial-based modulators commonly use graphene as a variable resistor, facing limitations in modulation depth due to resistive damping and graphene's finite conductivity.
- Achieving 100% modulation depth has been a persistent challenge in this field.
Purpose of the Study:
- To overcome the limitations of resistive damping in metamaterial-based terahertz modulators.
- To develop a novel approach for enhancing modulation depth and speed in terahertz devices.
- To explore the use of capacitive tuning with graphene in metamaterial resonators.
Main Methods:
- Embedding nanoscale graphene capacitors within the gaps of metamaterial resonators.
- Switching from resistive damping to capacitive tuning of the metamaterial resonance.
- Exciting the device from its substrate side to expand the optical modulation range.
Main Results:
- Demonstrated terahertz modulators with over four orders of magnitude modulation depth (45.7 dB at 1.68 THz and 40.1 dB at 2.15 THz).
- Achieved a reconfiguration speed of 30 MHz with electrically controlled solid-state devices.
- Enabled unity modulation with graphene conductivities below 0.7 mS.
Conclusions:
- The capacitive tuning approach significantly enhances modulation performance compared to resistive methods.
- This method is applicable to a wide range of metamaterial-based modulators utilizing 2D electron gases.
- The developed terahertz modulators open new possibilities for terahertz communications, imaging, and computing.
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