Sub-wavelength mid-infrared imaging of locally driven photocurrents using diamond campanile probes

Abstract

Precise and high efficiency concentration of mid-infrared (mid-IR) light into sub-wavelength volumes is essential for probing low-energy excitations and achieving strong field enhancements, which is hindered by absorption losses and coupling inefficiencies at long wavelengths. Here, we introduce a diamond-based metal-insulator-metal campanile probe that adiabatically compresses free-space mid-infrared light (10 μm) into ≈ 0.7 μm domain. Integrated into a scanning photovoltage microscope, the probe enables sub-wavelength mapping of locally driven photocurrents in graphene, resolving polarization-dependent and contact-sensitive responses at energies down to ≈ 0.1 eV. Experiments reveal a photocurrent signal density enhancement of 10 ³ , coupling light power efficiencies above 1%, and an 18-fold increase in near-field light flux density, in agreement with numerical simulations. Operation of the probe with quantum cascade and free-electron lasers demonstrates a robust, spectrally tunable platform for high-resolution exploration of low-energy carrier dynamics in atomically thin materials, opening opportunities for mid-IR optoelectronics and quantum photonics.

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BibTeX RIS

BibTeX

@article{medapalli2026subwavelength,
  title = {{Sub-wavelength mid-infrared imaging of locally driven photocurrents using diamond campanile probes}},
  author = {Rajasekhar Medapalli and Nathan D. Cottam and Khushboo Agarwal and Benjamin T. Dewes and Nils Dessmann and Sergio Gonzalez-Munoz and Wenjing Yan and Vaidotas Mišeikis and Sergey Kafanov and Rostislav V. Mikhaylovskiy and Samuel P. Jarvis and Camilla Coletti and Britta Redlich and Amalia Patanè and Oleg V. Kolosov},
  journal = {Communications Physics},
  year = {2026},
  month = nov,
  doi = {10.1038/s42005-026-02954-4},
  url = {https://www.nature.com/articles/s42005-026-02954-4},
  note = {CC BY 4.0},
}

RIS

TY  - JOUR
TI  - Sub-wavelength mid-infrared imaging of locally driven photocurrents using diamond campanile probes
AU  - Rajasekhar Medapalli
AU  - Nathan D. Cottam
AU  - Khushboo Agarwal
AU  - Benjamin T. Dewes
AU  - Nils Dessmann
AU  - Sergio Gonzalez-Munoz
AU  - Wenjing Yan
AU  - Vaidotas Mišeikis
AU  - Sergey Kafanov
AU  - Rostislav V. Mikhaylovskiy
AU  - Samuel P. Jarvis
AU  - Camilla Coletti
AU  - Britta Redlich
AU  - Amalia Patanè
AU  - Oleg V. Kolosov
PY  - 2026
DA  - 2026/11/03
JO  - Communications Physics
DO  - 10.1038/s42005-026-02954-4
UR  - https://www.nature.com/articles/s42005-026-02954-4
AB  - Precise and high efficiency concentration of mid-infrared (mid-IR) light into sub-wavelength volumes is essential for probing low-energy excitations and achieving strong field enhancements, which is hindered by absorption losses and coupling inefficiencies at long wavelengths. Here, we introduce a diamond-based metal-insulator-metal campanile probe that adiabatically compresses free-space mid-infrared light (10 μm) into ≈ 0.7 μm domain. Integrated into a scanning photovoltage microscope, the probe enables sub-wavelength mapping of locally driven photocurrents in graphene, resolving polarization-dependent and contact-sensitive responses at energies down to ≈ 0.1 eV. Experiments reveal a photocurrent signal density enhancement of 10 ³ , coupling light power efficiencies above 1%, and an 18-fold increase in near-field light flux density, in agreement with numerical simulations. Operation of the probe with quantum cascade and free-electron lasers demonstrates a robust, spectrally tunable platform for high-resolution exploration of low-energy carrier dynamics in atomically thin materials, opening opportunities for mid-IR optoelectronics and quantum photonics.
SN  - 2399-3650
ER  -

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