Recent news
Publications
Skyler P Selvin; Majid Esfandyarpour; Anqi Ji; Yan Joe Lee; Colin Yule; Jung-Hwan Song; Mohammad Taghinejad; Mark L Brongersma
Acoustic wave modulation of gap plasmon cavities Journal Article
In: Science, vol. 389, iss. 6759, pp. 516-520, 2025.
@article{selvin2025acoustic,
title = {Acoustic wave modulation of gap plasmon cavities},
author = {Skyler P Selvin and Majid Esfandyarpour and Anqi Ji and Yan Joe Lee and Colin Yule and Jung-Hwan Song and Mohammad Taghinejad and Mark L Brongersma},
url = {https://brongersma.stanford.edu/wp-content/uploads/2025/08/science.adv1728-2.pdf
https://www.science.org/stoken/author-tokens/ST-2800/full},
doi = {10.1126/science.adv1728},
year = {2025},
date = {2025-07-31},
urldate = {2025-07-31},
journal = {Science},
volume = {389},
issue = {6759},
pages = {516-520},
abstract = {The important role of metallic nanostructures in nanophotonics will expand if ways to electrically manipulate their optical resonances at high speed can be identified. We capitalized on electrically driven surface acoustic waves and the extreme light concentration afforded by gap plasmons to achieve this goal. We placed gold nanoparticles in a particle-on-mirror configuration with a few-nanometer-thick, compressible polymer spacer. Surface acoustic waves were then used to tune light scattering at speeds approaching the gigahertz regime. We observed evidence that the surface acoustic waves produced mechanical deformations in the polymer and that ensuing nonlinear mechanical dynamics led to unexpectedly large levels of strain and spectral tuning. Our approach provides a design strategy for electrically driven dynamic metasurfaces and fundamental explorations of high-frequency, polymer dynamics in ultraconfined geometries.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The important role of metallic nanostructures in nanophotonics will expand if ways to electrically manipulate their optical resonances at high speed can be identified. We capitalized on electrically driven surface acoustic waves and the extreme light concentration afforded by gap plasmons to achieve this goal. We placed gold nanoparticles in a particle-on-mirror configuration with a few-nanometer-thick, compressible polymer spacer. Surface acoustic waves were then used to tune light scattering at speeds approaching the gigahertz regime. We observed evidence that the surface acoustic waves produced mechanical deformations in the polymer and that ensuing nonlinear mechanical dynamics led to unexpectedly large levels of strain and spectral tuning. Our approach provides a design strategy for electrically driven dynamic metasurfaces and fundamental explorations of high-frequency, polymer dynamics in ultraconfined geometries.
Won-Jae Joo; Jisoo Kyoung; Majid Esfandyarpour; Sung-Hoon Lee; Hyun Koo; Sunjin Song; Young-Nam Kwon; Seok Ho Song; Jun Cheol Bae; Ara Jo; Myong-Jong Kwon; Sung Hyun Han; Sung-Han Kim; Sungwoo Hwang; Mark L. Brongersma
Metasurface-driven OLED displays beyond 10,000 pixels per inch Journal Article
In: Science, vol. 370, no. 6515, pp. 459-463, 2020.
@article{joo2020metasurface,
title = {Metasurface-driven OLED displays beyond 10,000 pixels per inch},
author = {Won-Jae Joo and Jisoo Kyoung and Majid Esfandyarpour and Sung-Hoon Lee and Hyun Koo and Sunjin Song and Young-Nam Kwon and Seok Ho Song and Jun Cheol Bae and Ara Jo and Myong-Jong Kwon and Sung Hyun Han and Sung-Han Kim and Sungwoo Hwang and Mark L. Brongersma},
doi = {10.1126/science.abc8530},
year = {2020},
date = {2020-10-23},
journal = {Science},
volume = {370},
number = {6515},
pages = {459-463},
abstract = {Optical metasurfaces are starting to find their way into integrated devices, where they can enhance and control the emission, modulation, dynamic shaping, and detection of light waves. In this study, we show that the architecture of organic light-emitting diode (OLED) displays can be completely reenvisioned through the introduction of nanopatterned metasurface mirrors. In the resulting meta-OLED displays, different metasurface patterns define red, green, and blue pixels and ensure optimized extraction of these colors from organic, white light emitters. This new architecture facilitates the creation of devices at the ultrahigh pixel densities (\>10,000 pixels per inch) required in emerging display applications (for instance, augmented reality) that use scalable nanoimprint lithography. The fabricated pixels also offer twice the luminescence efficiency and superior color purity relative to standard color-filtered white OLEDs.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Optical metasurfaces are starting to find their way into integrated devices, where they can enhance and control the emission, modulation, dynamic shaping, and detection of light waves. In this study, we show that the architecture of organic light-emitting diode (OLED) displays can be completely reenvisioned through the introduction of nanopatterned metasurface mirrors. In the resulting meta-OLED displays, different metasurface patterns define red, green, and blue pixels and ensure optimized extraction of these colors from organic, white light emitters. This new architecture facilitates the creation of devices at the ultrahigh pixel densities (>10,000 pixels per inch) required in emerging display applications (for instance, augmented reality) that use scalable nanoimprint lithography. The fabricated pixels also offer twice the luminescence efficiency and superior color purity relative to standard color-filtered white OLEDs.
Vrinda Thareja; Majid Esfandyarpour; Pieter G. Kik; Mark L. Brongersma
Anisotropic Metasurfaces as Tunable SERS Substrates for 2D Materials Journal Article
In: ACS Photonics, vol. 6, no. 8, pp. 1996–2004, 2019.
@article{thareja2019anisotropic,
title = {Anisotropic Metasurfaces as Tunable SERS Substrates for 2D Materials},
author = {Vrinda Thareja and Majid Esfandyarpour and Pieter G. Kik and Mark L. Brongersma},
doi = {10.1021/acsphotonics.9b00416},
year = {2019},
date = {2019-06-20},
journal = {ACS Photonics},
volume = {6},
number = {8},
pages = {1996\textendash2004},
abstract = {The reflection of light from metallic mirrors results in a near-zero electric field at their surface. This precludes strong light-matter interaction between such mirrors and two-dimensional (2D) materials placed in direct contact with them. Patterning of the metal surfaces with sub-wavelength grooves can produce anisotropic metasurfaces that offer robust enhancements in the magnitude and control over the direction of the surface fields. Here, we use this control to analyze the Raman tensor for vibrational modes of atomically-thin graphene. The anisotropic nature of the grooves leads to different Raman signal enhancement for the G (25 times) and 2D (50 times) Raman peaks of graphene for optimized groove dimensions. A notable suppression of these peaks by 40% for specific groove dimensions is also achieved. These findings suggest the use of metasurfaces as tunable surface enhanced Raman scattering substrates to study the vibrational modes of 2D materials with reduced background signals.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The reflection of light from metallic mirrors results in a near-zero electric field at their surface. This precludes strong light-matter interaction between such mirrors and two-dimensional (2D) materials placed in direct contact with them. Patterning of the metal surfaces with sub-wavelength grooves can produce anisotropic metasurfaces that offer robust enhancements in the magnitude and control over the direction of the surface fields. Here, we use this control to analyze the Raman tensor for vibrational modes of atomically-thin graphene. The anisotropic nature of the grooves leads to different Raman signal enhancement for the G (25 times) and 2D (50 times) Raman peaks of graphene for optimized groove dimensions. A notable suppression of these peaks by 40% for specific groove dimensions is also achieved. These findings suggest the use of metasurfaces as tunable surface enhanced Raman scattering substrates to study the vibrational modes of 2D materials with reduced background signals.
Majid Esfandyarpour; Alberto G. Curto; Pieter G. Kik; Nader Engheta; Mark L. Brongersma
Optical emission near a high-impedance mirror Journal Article
In: Nature Communications, vol. 9, no. 3224, 2018.
@article{esfandyarpour2018optical,
title = {Optical emission near a high-impedance mirror},
author = {Majid Esfandyarpour and Alberto G. Curto and Pieter G. Kik and Nader Engheta and Mark L. Brongersma },
doi = {10.1038/s41467-018-05505-w},
year = {2018},
date = {2018-08-13},
journal = {Nature Communications},
volume = {9},
number = {3224},
abstract = {Solid state light emitters rely on metallic contacts with a high sheet-conductivity for effective charge injection. Unfortunately, such contacts also support surface plasmon polariton and lossy wave excitations that dissipate optical energy into the metal and limit the external quantum efficiency. Here, inspired by the concept of radio-frequency high-impedance surfaces and their use in conformal antennas we illustrate how electrodes can be nanopatterned to simultaneously provide a high DC electrical conductivity and high-impedance at optical frequencies. Such electrodes do not support SPPs across the visible spectrum and greatly suppress dissipative losses while facilitating a desirable Lambertian emission profile. We verify this concept by studying the emission enhancement and photoluminescence lifetime for a dye emitter layer deposited on the electrodes.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Solid state light emitters rely on metallic contacts with a high sheet-conductivity for effective charge injection. Unfortunately, such contacts also support surface plasmon polariton and lossy wave excitations that dissipate optical energy into the metal and limit the external quantum efficiency. Here, inspired by the concept of radio-frequency high-impedance surfaces and their use in conformal antennas we illustrate how electrodes can be nanopatterned to simultaneously provide a high DC electrical conductivity and high-impedance at optical frequencies. Such electrodes do not support SPPs across the visible spectrum and greatly suppress dissipative losses while facilitating a desirable Lambertian emission profile. We verify this concept by studying the emission enhancement and photoluminescence lifetime for a dye emitter layer deposited on the electrodes.
Steven J. Madsen; Majid Esfandyarpour; Mark L. Brongersma; Robert Sinclair
Observing Plasmon Damping Due to Adhesion Layers in Gold Nanostructures Using Electron Energy Loss Spectroscopy Journal Article
In: ACS Photonics, vol. 4, no. 2, pp. 268–274, 2017.
@article{madsen2017observing,
title = {Observing Plasmon Damping Due to Adhesion Layers in Gold Nanostructures Using Electron Energy Loss Spectroscopy},
author = {Steven J. Madsen and Majid Esfandyarpour and Mark L. Brongersma and Robert Sinclair},
doi = {10.1021/acsphotonics.6b00525},
year = {2017},
date = {2017-01-13},
journal = {ACS Photonics},
volume = {4},
number = {2},
pages = { 268\textendash274},
abstract = {Gold plasmonic nanostructures with several different adhesion layers have been studied with monochromated electron energy loss spectroscopy in the scanning transmission electron microscope (STEM-EELS) and with surface-enhanced Raman spectroscopy (SERS). Compared to samples with no adhesion layer, those with 2 nm of Cr or Ti show broadened, lower intensity plasmon peaks as measured with EELS. This broadening is observed in both optically active (“bright”) and inactive (“dark”) plasmon modes. When the former are probed with SERS, the signal enhancement factor is lower for samples with Cr or Ti, another indication of reduced plasmon resonance. This work illustrates the capability of STEM-EELS to provide direct near-field measurement of changes in plasmon excitation probability with nanoscale spatial resolution. Additionally, it demonstrates that applications requiring high SERS enhancement, such as biomarker detection and cancer diagnostics, can be improved by avoiding the use of a metallic adhesion layer.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Gold plasmonic nanostructures with several different adhesion layers have been studied with monochromated electron energy loss spectroscopy in the scanning transmission electron microscope (STEM-EELS) and with surface-enhanced Raman spectroscopy (SERS). Compared to samples with no adhesion layer, those with 2 nm of Cr or Ti show broadened, lower intensity plasmon peaks as measured with EELS. This broadening is observed in both optically active (“bright”) and inactive (“dark”) plasmon modes. When the former are probed with SERS, the signal enhancement factor is lower for samples with Cr or Ti, another indication of reduced plasmon resonance. This work illustrates the capability of STEM-EELS to provide direct near-field measurement of changes in plasmon excitation probability with nanoscale spatial resolution. Additionally, it demonstrates that applications requiring high SERS enhancement, such as biomarker detection and cancer diagnostics, can be improved by avoiding the use of a metallic adhesion layer.
Søren Raza; Majid Esfandyarpour; Ai Leen Koh; N. Asger Mortensen; Mark L. Brongersma; Sergey I. Bozhevolnyi
Electron energy-loss spectroscopy of branched gap plasmon resonators Journal Article
In: Nat. Commun., vol. 7, pp. 13790, 2016.
@article{Raza:2016,
title = {Electron energy-loss spectroscopy of branched gap plasmon resonators},
author = {S\oren Raza and Majid Esfandyarpour and Ai Leen Koh and N. Asger Mortensen and Mark L. Brongersma and Sergey I. Bozhevolnyi},
doi = {10.1038/ncomms13790},
year = {2016},
date = {2016-12-16},
journal = {Nat. Commun.},
volume = {7},
pages = {13790},
abstract = {The miniaturization of integrated optical circuits below the diffraction limit for high-speed manipulation of information is one of the cornerstones in plasmonics research. By coupling to surface plasmons supported on nanostructured metallic surfaces, light can be confined to the nanoscale, enabling the potential interface to electronic circuits. In particular, gap surface plasmons propagating in an air gap sandwiched between metal layers have shown extraordinary mode confinement with significant propagation length. In this work, we unveil the optical properties of gap surface plasmons in silver nanoslot structures with widths of only 25 nm. We fabricate linear, branched and cross-shaped nanoslot waveguide components, which all support resonances due to interference of counter-propagating gap plasmons. By exploiting the superior spatial resolution of a scanning transmission electron microscope combined with electron energy-loss spectroscopy, we experimentally show the propagation, bending and splitting of slot gap plasmons.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The miniaturization of integrated optical circuits below the diffraction limit for high-speed manipulation of information is one of the cornerstones in plasmonics research. By coupling to surface plasmons supported on nanostructured metallic surfaces, light can be confined to the nanoscale, enabling the potential interface to electronic circuits. In particular, gap surface plasmons propagating in an air gap sandwiched between metal layers have shown extraordinary mode confinement with significant propagation length. In this work, we unveil the optical properties of gap surface plasmons in silver nanoslot structures with widths of only 25 nm. We fabricate linear, branched and cross-shaped nanoslot waveguide components, which all support resonances due to interference of counter-propagating gap plasmons. By exploiting the superior spatial resolution of a scanning transmission electron microscope combined with electron energy-loss spectroscopy, we experimentally show the propagation, bending and splitting of slot gap plasmons.
