Brongersma Group Plasmonics and Photonics at Stanford University

@article{taghinejad2025ion,

title = {Ion-assisted nanoscale material engineering in atomic layers},

author = {Hossein Taghinejad and Mohammad Taghinejad and Sajjad Abdollahramezani and Qitong Li and Eric V Woods and Mengkun Tian and Ali A Eftekhar and Yuanqi Lyu and Xiang Zhang and Pulickel M Ajayan and Wenshan Cai and Mark L Brongersma and James G Analytis and Ali Adibi},

doi = {10.1021/acs.nanolett.5c02040},

year  = {2025},

date = {2025-06-13},

urldate = {2025-06-13},

journal = {Nano Letters},

volume = {25},

issue = {25},

pages = {10123-10130},

abstract = {Achieving deterministic control over the properties of low-dimensional materials with nanoscale precision is a long-sought goal. Mastering this capability has a transformative effect on the design of multifunctional electrical and optical devices. Here, we present an ion-assisted synthetic technique that enables precise control over the material composition and energy landscape of two-dimensional (2D) atomic crystals. Our method transforms binary transition-metal dichalcogenides, like MoSe2, into ternary MoS2αSe2(1−α) alloys with systematically adjustable compositions, α. By piecewise assembly of the lateral, compositionally modulated MoS2αSe2(1−α) segments within 2D atomic layers, we present a synthetic pathway toward the realization of multicompositional designer materials. Our technique enables the fabrication of advanced 2D structures with arbitrary boundaries, dimensions as small as 30 nm, and fully customizable energy landscapes. Our optical characterizations further showcase the potential for implementing tailored optoelectronics in these engineered 2D crystals.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{guarneri2025dynamic,

title = {Dynamic Excitonic Beam Switching with Atomically‐Thin Binary Blazed Gratings},

author = {Ludovica Guarneri and Thomas Bauer and Qitong Li and Jung‐Hwan Song and Skyler P Selvin and Ashley P Saunders and Fang Liu and Mark L Brongersma and Jorik van de Groep},

doi = {10.1002/adom.202403257},

year  = {2025},

date = {2025-05-12},

urldate = {2025-05-12},

journal = {Advanced Optical Materials},

volume = {13},

issue = {15},

pages = {2403257},

abstract = {Beam steering metasurfaces are ultra-compact optical coatings that offer on-demand redirection of optical power to specific diffraction orders. To achieve this, spatial gradients are commonly introduced in the phase of light scattered by plasmon or Mie resonant nanoparticles within the metasurface grating's unit cell. However, these phase gradients are oftentimes difficult to tune post-fabrication. Recently, excitons in monolayer 2D semiconductors have emerged as a new metasurface building block, due to their strong and electrically-tunable resonant light-matter interaction. These 2D excitonic metasurfaces offer the tantalizing prospect of beam switching within a single monolayer. Here, it is demonstrated how the 2D analog of binary blazed gratings enables such beam switching by mere nanopatterning of a large monolayer WS2, even though nanoscale ribbons of WS2 do not support geometrical resonances. By introducing a gradient in the nanoribbon width within the metasurface unit cell, an amplitude gradient combined with a small phase gradient in the scattered fields results in asymmetric diffraction efficiencies. Using a scattered-field analysis, it is shown that these gradients can be further engineered via interference effects with the substrate reflection. Finally, the electrical tunability of the exciton resonance is leveraged to achieve selective and dynamic beam switching with an atomically-thin metasurface.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{li2024optical,

title = {Optical devices as thin as atoms},

author = {Melissa Li and Qitong Li and Mark L Brongersma and Harry A Atwater},

doi = {10.1126/science.adk7707},

year  = {2024},

date = {2024-12-13},

urldate = {2024-12-13},

journal = {Science},

volume = {386},

issue = {6727},

pages = {1226-1228},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{ha2024optoelectronic,

title = {Optoelectronic metadevices},

author = {Son Tung Ha and Qitong Li and Joel KW Yang and Hilmi Volkan Demir and Mark L Brongersma and Arseniy I Kuznetsov},

doi = {10.1126/science.adm7442},

year  = {2024},

date = {2024-11-29},

urldate = {2024-11-29},

journal = {Science},

volume = {386},

issue = {6725},

pages = {7442},

abstract = {Metasurfaces have introduced new opportunities in photonic design by offering unprecedented, nanoscale control over optical wavefronts. These artificially structured layers have largely been used to passively manipulate the flow of light by controlling its phase, amplitude, and polarization. However, they can also dynamically modulate these quantities and manipulate fundamental light absorption and emission processes. These valuable traits can extend their application domain to chipscale optoelectronics and conceptually new optical sources, displays, spatial light modulators, photodetectors, solar cells, and imaging systems. New opportunities and challenges have also emerged in the materials and device integration with existing technologies. This Review aims to consolidate the current research landscape and provide perspectives on metasurface capabilities specific to optoelectronic devices, giving new direction to future research and development efforts in academia and industry.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{guarneri2024temperature,

title = {Temperature-Dependent Excitonic Light Manipulation with Atomically Thin Optical Elements},

author = {Ludovica Guarneri and Qitong Li and Thomas Bauer and Jung-Hwan Song and Ashley P Saunders and Fang Liu and Mark L Brongersma and Jorik van de Groep},

doi = {10.1021/acs.nanolett.4c00694},

year  = {2024},

date = {2024-04-05},

journal = {Nano Letters},

abstract = {Monolayer 2D semiconductors, such as WS2, exhibit uniquely strong light\textendashmatter interactions due to exciton resonances that enable atomically thin optical elements. Similar to geometry-dependent plasmon and Mie resonances, these intrinsic material resonances offer coherent and tunable light scattering. Thus far, the impact of the excitons’ temporal dynamics on the performance of such excitonic metasurfaces remains unexplored. Here, we show how the excitonic decay rates dictate the focusing efficiency of an atomically thin lens carved directly out of exfoliated monolayer WS2. By isolating the coherent exciton radiation from the incoherent background in the focus of the lens, we obtain a direct measure of the role of exciton radiation in wavefront shaping. Furthermore, we investigate the influence of exciton\textendashphonon scattering by characterizing the focusing efficiency as a function of temperature, demonstrating an increased optical efficiency at cryogenic temperatures. Our results provide valuable insights into the role of excitonic light scattering in 2D nanophotonic devices.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{taghinejad2023determining,

title = {Determining hot-carrier transport dynamics from terahertz emission},

author = {Mohammad Taghinejad and Chenyi Xia and Martin Hrton and Kyu-Tae Lee and Andrew S Kim and Qitong Li and Burak Guzelturk and Radek Kalousek and Fenghao Xu and Wenshan Cai and Aaron M Lindenberg and Mark L Brongersma},

doi = {10.1126/science.adj5612},

year  = {2023},

date = {2023-10-20},

urldate = {2023-10-20},

journal = {Science},

volume = {382},

issue = {6668},

pages = {299-305},

abstract = {Understanding the ultrafast excitation and transport dynamics of plasmon-driven hot carriers is critical to the development of optoelectronics, photochemistry, and solar-energy harvesting. However, the ultrashort time and length scales associated with the behavior of these highly out-of-equilibrium carriers have impaired experimental verification of ab initio quantum theories. Here, we present an approach to studying plasmonic hot-carrier dynamics that analyzes the temporal waveform of coherent terahertz bursts radiated by photo-ejected hot carriers from designer nano-antennas with a broken symmetry. For ballistic carriers ejected from gold antennas, we find an ~11-femtosecond timescale composed of the plasmon lifetime and ballistic transport time. Polarization- and phase-sensitive detection of terahertz fields further grant direct access to their ballistic transport trajectory. Our approach opens explorations of ultrafast carrier dynamics in optically excited nanostructures.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}