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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.
Keisuke Ozawa; Hiroshi Sugimoto; Daisuke Shima; Tatsuki Hinamoto; Mojtaba Karimi Habil; Yan Joe Lee; Søren Raza; Keisuke Imaeda; Kosei Ueno; Mark L Brongersma; Minoru Fujii
Routing Light Emission from Monolayer MoS2 by Mie Resonances of Crystalline Silicon Nanospheres Journal Article
In: ACS Applied Optical Materials, vol. 3, iss. 2, pp. 375-382, 2025.
@article{ozawa2025routing,
title = {Routing Light Emission from Monolayer MoS2 by Mie Resonances of Crystalline Silicon Nanospheres},
author = {Keisuke Ozawa and Hiroshi Sugimoto and Daisuke Shima and Tatsuki Hinamoto and Mojtaba Karimi Habil and Yan Joe Lee and S\oren Raza and Keisuke Imaeda and Kosei Ueno and Mark L Brongersma and Minoru Fujii},
doi = {10.1021/acsaom.4c00495},
year = {2025},
date = {2025-02-15},
journal = {ACS Applied Optical Materials},
volume = {3},
issue = {2},
pages = {375-382},
abstract = {A dielectric Mie-resonant nanoantenna is capable of controlling the directionality of the emission from nearby quantum emitters through the excitation of multiple degenerate Mie resonances. A crystalline silicon nanosphere (Si NS) is a promising candidate for a dielectric nanoantenna because crystalline Si has a large refractive index (3.8 at 650 nm) and the small imaginary part of a complex refractive index (0.015 at 650 nm) as an optical material. In this work, we control the emission directionality of excitons supported by monolayer transition metal dichalcogenides (1L-TMDCs) using a Si NS. We first discuss the condition to extract the emission preferentially toward the Si NS side from the analytical calculations. We then study the photoluminescence (PL) of 1L-TMDCs on which differently sized single Si NSs are placed. We show that the PL spectral shape strongly depends on the emission direction, and that the emission toward the Si NS side (top) with respect to the opposite side (bottom) is the largest at a wavelength between the magnetic dipole and electric dipole Mie resonances of a Si NS. Finally, we quantitatively discuss the spectral shape of the top-to-bottom ratio from numerical simulations.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
A dielectric Mie-resonant nanoantenna is capable of controlling the directionality of the emission from nearby quantum emitters through the excitation of multiple degenerate Mie resonances. A crystalline silicon nanosphere (Si NS) is a promising candidate for a dielectric nanoantenna because crystalline Si has a large refractive index (3.8 at 650 nm) and the small imaginary part of a complex refractive index (0.015 at 650 nm) as an optical material. In this work, we control the emission directionality of excitons supported by monolayer transition metal dichalcogenides (1L-TMDCs) using a Si NS. We first discuss the condition to extract the emission preferentially toward the Si NS side from the analytical calculations. We then study the photoluminescence (PL) of 1L-TMDCs on which differently sized single Si NSs are placed. We show that the PL spectral shape strongly depends on the emission direction, and that the emission toward the Si NS side (top) with respect to the opposite side (bottom) is the largest at a wavelength between the magnetic dipole and electric dipole Mie resonances of a Si NS. Finally, we quantitatively discuss the spectral shape of the top-to-bottom ratio from numerical simulations.
Qitong Li; Jung-Hwan Song; Fenghao Xu; Jorik van de Groep; Jiho Hong; Alwin Daus; Yan Joe Lee; Amalya C Johnson; Eric Pop; Fang Liu; Mark L Brongersma
A Purcell-enabled monolayer semiconductor free-space optical modulator Journal Article
In: Nature Photonics, vol. 17, iss. 10, pp. 897-903, 2023.
@article{li2023purcell,
title = {A Purcell-enabled monolayer semiconductor free-space optical modulator},
author = {Qitong Li and Jung-Hwan Song and Fenghao Xu and Jorik van de Groep and Jiho Hong and Alwin Daus and Yan Joe Lee and Amalya C Johnson and Eric Pop and Fang Liu and Mark L Brongersma},
doi = {10.1038/s41566-023-01250-9},
year = {2023},
date = {2023-07-23},
urldate = {2023-07-23},
journal = {Nature Photonics},
volume = {17},
issue = {10},
pages = {897-903},
abstract = {Dephasing and non-radiative decay processes limit the performance of a wide variety of quantum devices at room temperature. Here we illustrate a general pathway to notably reduce the detrimental impact of these undesired effects through photonic design of the device electrodes. Our design facilitates a large Purcell enhancement that speeds up competing, desired radiative decay while also enabling convenient electrical gating and charge injection functions. We demonstrate the concept with a free-space optical modulator based on an atomically thin semiconductor. By engineering the plasmonic response of a nanopatterned silver gate pad, we successfully enhance the radiative decay rate of excitons in a tungsten disulfide monolayer by one order of magnitude to create record-high modulation efficiencies for this class of materials at room temperature. We experimentally observe a 10% reflectance change as well as 3 dB signal modulation, corresponding to a 20-fold enhancement compared with modulation using a suspended monolayer in vacuum. We also illustrate how dynamic control of light fields can be achieved with designer surface patterns. This research highlights the benefits of applying radiative decay engineering as a powerful tool in creating high-performance devices that complements substantial efforts to improve the quality of materials.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Dephasing and non-radiative decay processes limit the performance of a wide variety of quantum devices at room temperature. Here we illustrate a general pathway to notably reduce the detrimental impact of these undesired effects through photonic design of the device electrodes. Our design facilitates a large Purcell enhancement that speeds up competing, desired radiative decay while also enabling convenient electrical gating and charge injection functions. We demonstrate the concept with a free-space optical modulator based on an atomically thin semiconductor. By engineering the plasmonic response of a nanopatterned silver gate pad, we successfully enhance the radiative decay rate of excitons in a tungsten disulfide monolayer by one order of magnitude to create record-high modulation efficiencies for this class of materials at room temperature. We experimentally observe a 10% reflectance change as well as 3 dB signal modulation, corresponding to a 20-fold enhancement compared with modulation using a suspended monolayer in vacuum. We also illustrate how dynamic control of light fields can be achieved with designer surface patterns. This research highlights the benefits of applying radiative decay engineering as a powerful tool in creating high-performance devices that complements substantial efforts to improve the quality of materials.
Hiroto Shinomiya; Hiroshi Sugimoto; Tatsuki Hinamoto; Yan Joe Lee; Mark L. Brongersma; Minoru Fujii
Enhanced Light Emission from Monolayer MoS2 by Doubly Resonant Spherical Si Nanoantennas Journal Article
In: ACS Photonics, vol. 9, iss. 5, pp. 1741-1747, 2022.
@article{shinomiya2022enhancedb,
title = {Enhanced Light Emission from Monolayer MoS2 by Doubly Resonant Spherical Si Nanoantennas},
author = {Hiroto Shinomiya and Hiroshi Sugimoto and Tatsuki Hinamoto and Yan Joe Lee and Mark L. Brongersma and Minoru Fujii},
doi = {10.1021/acsphotonics.2c00142},
year = {2022},
date = {2022-04-19},
journal = {ACS Photonics},
volume = {9},
issue = {5},
pages = {1741-1747},
abstract = {Optical antennas provide a powerful tool to control local photonic environments and enhance light emission from two-dimensional transition-metal dichalcogenides. Dielectric nanoantennas with multipolar Mie resonances bring unique advantages for achieving simultaneous enhancement of the absorption and emission processes. Here, we achieve a strong modification of the photoluminescence (PL) behavior of monolayer MoS2 by a spherical nanoparticle (NP) of crystalline silicon (Si) that works as a double resonance nanoantenna. From theoretical calculations for in-plane dipoles placed beneath a Si NP nanoantenna with different sizes, we explore optimal conditions for the double resonances. Then, we develop a heterostructure composed of a Si NP and a monolayer MoS2 sheet with a comparable diameter and investigate the scattering, PL, and PL excitation spectra across a wide Si NP size range. We show that the spectral shape is significantly modified and PL intensity is enhanced up to ∼10-fold due to the coupling of the excitation process to the magnetic quadrupole resonance and the emission process to the magnetic dipole resonance.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Optical antennas provide a powerful tool to control local photonic environments and enhance light emission from two-dimensional transition-metal dichalcogenides. Dielectric nanoantennas with multipolar Mie resonances bring unique advantages for achieving simultaneous enhancement of the absorption and emission processes. Here, we achieve a strong modification of the photoluminescence (PL) behavior of monolayer MoS2 by a spherical nanoparticle (NP) of crystalline silicon (Si) that works as a double resonance nanoantenna. From theoretical calculations for in-plane dipoles placed beneath a Si NP nanoantenna with different sizes, we explore optimal conditions for the double resonances. Then, we develop a heterostructure composed of a Si NP and a monolayer MoS2 sheet with a comparable diameter and investigate the scattering, PL, and PL excitation spectra across a wide Si NP size range. We show that the spectral shape is significantly modified and PL intensity is enhanced up to ∼10-fold due to the coupling of the excitation process to the magnetic quadrupole resonance and the emission process to the magnetic dipole resonance.
Burak Aslan; Colin Yule; Yifei Yu; Yan Joe Lee; Tony F. Heinz; Linyou Cao; Mark L. Brongersma
Excitons in strained and suspended monolayer WSe2 Journal Article
In: 2D Materials, vol. 9, no. 1, pp. 015002, 2021.
@article{aslan2021excitons,
title = {Excitons in strained and suspended monolayer WSe2},
author = {Burak Aslan and Colin Yule and Yifei Yu and Yan Joe Lee and Tony F. Heinz and Linyou Cao and Mark L. Brongersma},
doi = {10.1088/2053-1583/ac2d15},
year = {2021},
date = {2021-10-21},
urldate = {2021-10-21},
journal = {2D Materials},
volume = {9},
number = {1},
pages = {015002},
abstract = {We study suspended membranes of atomically thin WSe2 as hosts of excitons. We perform optical reflectance measurements to probe the exciton physics and obtain the peak energies for the 1$s$, 2$s$, and 3$s$ states of the $A$ exciton in suspended WSe2 and consider supported membranes as a reference. We find that elimination of the influence of the dielectric environment enables a strong electron\textendashhole interaction and a concomitant increase in the exciton binding energy in suspended monolayer (1L) WSe2. Based on the experimental results, we calculate the excitonic binding energies by employing the recently developed quantum electrostatic heterostructure model and the commonly employed Rytova\textendashKeldysh potential model. We see that the binding energy of the ground state $A$ exciton increases from about 0.3 eV (on a substrate) to above 0.4 eV (suspended). We also exploit the tunability of the excitons in suspended samples via mechanical strain. By applying external gas pressure of 2.72 atm to a 1L suspended over a circular hole of 8 μm diameter, we strain the WSe2 and obtain a reversible 0.15 eV redshift in the exciton resonance. The linewidth of the $A$ exciton decreases by more than half, from about 50 to 20 meV under 1.5% biaxial strain at room temperature. This line narrowing is due to the suppression of intervalley exciton\textendashphonon scattering. By making use of the observed strain-dependent optical signatures, we infer the two-dimensional (2D) elastic moduli of 1L and 2L WSe2. Our results exemplify the use of suspended 2D materials as novel systems for fundamental studies, as well as for strong and dynamic tuning of their optical properties.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We study suspended membranes of atomically thin WSe2 as hosts of excitons. We perform optical reflectance measurements to probe the exciton physics and obtain the peak energies for the 1$s$, 2$s$, and 3$s$ states of the $A$ exciton in suspended WSe2 and consider supported membranes as a reference. We find that elimination of the influence of the dielectric environment enables a strong electron–hole interaction and a concomitant increase in the exciton binding energy in suspended monolayer (1L) WSe2. Based on the experimental results, we calculate the excitonic binding energies by employing the recently developed quantum electrostatic heterostructure model and the commonly employed Rytova–Keldysh potential model. We see that the binding energy of the ground state $A$ exciton increases from about 0.3 eV (on a substrate) to above 0.4 eV (suspended). We also exploit the tunability of the excitons in suspended samples via mechanical strain. By applying external gas pressure of 2.72 atm to a 1L suspended over a circular hole of 8 μm diameter, we strain the WSe2 and obtain a reversible 0.15 eV redshift in the exciton resonance. The linewidth of the $A$ exciton decreases by more than half, from about 50 to 20 meV under 1.5% biaxial strain at room temperature. This line narrowing is due to the suppression of intervalley exciton–phonon scattering. By making use of the observed strain-dependent optical signatures, we infer the two-dimensional (2D) elastic moduli of 1L and 2L WSe2. Our results exemplify the use of suspended 2D materials as novel systems for fundamental studies, as well as for strong and dynamic tuning of their optical properties.
