Brongersma Group Plasmonics and Photonics at Stanford University

@article{rufangura2025near,

title = {Near unity narrowband infrared thermal emitters on silicon with silicon carbide-germanium metasurfaces},

author = {Patrick Rufangura and Yiyang Cui and Huan Liu and Johan D Carlstrom and Kenneth Crozier and Mark L Brongersma and Yang Yang and Francesca Iacopi},

doi = {10.1063/5.0271574},

year  = {2025},

date = {2025-08-01},

journal = {APL Photonics},

volume = {10},

issue = {8},

abstract = {Traditional thermal emitters are characterized by an incoherent broadband emission spectrum. However, narrowband coherent thermal emission with a high-quality factor in thermally stable materials is highly desirable for applications such as sensing, thermal energy management, thermophotovoltaic systems, and other infrared technologies. Recent advances in engineered nanostructured polaritonic materials, particularly polar dielectric materials in the mid-infrared (MIR) regime, have enabled new approaches to tailoring narrowband coherent thermal emission. The use of low-loss phonon polaritons in thermally stable silicon carbide provides a promising route to MIR thermal emission. In this work, we demonstrate narrowband, near-unity MIR thermal emission by coupling coherent surface phonon polaritons in a SiC layer with a subwavelength germanium grating on a silicon substrate. The demonstrated polarization-dependent thermal emitter, compatible with silicon fabrication technologies for seamless on-chip photonic integration, exhibits narrowband high emissivity (\>90%) at a wavelength of ∼11 μm. Furthermore, we show that these emitters achieve experimental quality factors well above 100 while maintaining significant emission across a wide range of incident angles for MIR radiation.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@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}

}

@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{dagli2025ghz,

title = {GHz‐Speed Wavefront Shaping Metasurface Modulators Enabled by Resonant Electro‐Optic Nanoantennas},

author = {Sahil Dagli and Jiyong Shim and Hamish Carr Delgado and Halleh B Balch and Sajjad Abdollahramezani and Chih‐Yi Chen and Varun Dolia and Elissa Klopfer and Jefferson Dixon and Jack Hu and Babatunde Ogunlade and Jung‐Hwan Song and Mark L Brongersma and David Barton and Jennifer A Dionne},

doi = {10.1002/adma.202506790},

year  = {2025},

date = {2025-03-11},

journal = {Advanced Materials},

volume = {e06790},

abstract = {Electrically tunable metasurfaces that control the amplitude and phase of light through biasing of nanoscale antennas present a route to compact modulator devices. However, most platforms face limitations in bandwidth, optical efficiency, and tuning response. Electro-optically tunable metasurfaces achieving both GHz amplitude modulation and transmissive wavefront shaping in the telecom range are presented. The resonant electro-optic nanoantenna design consists of a silicon nanobar atop thin-film lithium niobate, with gold electrodes. The nanobar is a periodically perturbed optical waveguide that supports high quality factor (Q \> 1000) guided mode resonances excited with free-space light. Voltage biasing the lithium niobate tunes its refractive index, modulating the resonance of the nanobar through evanescent mode overlap. Absolute transmittance modulation of 7.1% with ±5 V applied voltage is demonstrated, and the modulation dependence on the resonance quality factor is shown. Additionally, the modulation bandwidth of these devices exceeds 800 MHz, and the electrode limitations on this bandwidth are studied. Finally, how this resonant antenna platform can enable wavefront shaping metasurfaces is shown. A beamsplitting metasurface device is demonstrated, whose diffraction efficiency can be modulated with a bandwidth of 1.03 GHz. The high-speed modulation and wavefront control capabilities of this platform provide a foundation for compact, high-bandwidth free-space communications and sensing devices.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{doshi2025thermal,

title = {Thermal Processing Creates Water‐Stable PEDOT: PSS Films for Bioelectronics},

author = {Siddharth Doshi and Margaux OA Forner and Pingyu Wang and Salim El Hadwe and Amy T Jin and Gerwin Dijk and Kenneth Brinson and Juhwan Lim and Antonio Dominguez‐Alfaro and Carina Yi Jing Lim and Alberto Salleo and Damiano G Barone and Guosong Hong and Mark L Brongersma and Nicholas A Melosh and George G Malliaras and Scott T Keene},

doi = {10.1002/adma.202415827},

year  = {2025},

date = {2025-03-03},

urldate = {2025-03-03},

journal = {Advanced Materials},

volume = {37},

issue = {13},

pages = {2415827},

abstract = {Organic mixed ionic-electronic conductors have emerged as a key material for the development of bioelectronic devices due to their soft mechanical properties, biocompatibility, and high volumetric capacitance. In particular, PEDOT:PSS has become a choice material because it is highly conductive, easily processible, and commercially available. However, PEDOT:PSS is dispersible in water, leading to delamination of films when exposed to biological environments. For this reason, chemical cross\textendashlinking agents such as (3-glycidyloxypropyl)trimethoxysilane (GOPS) are used to stabilize PEDOT:PSS films in water, but at the cost of decreased electrical performance. Here, it is shown that PEDOT:PSS thin films become water-stable by simply baking at high temperatures (\>150 °C) for a short time (≈ 2 min). It is shown that heat-treated PEDOT:PSS films are as stable as their chemically-cross\textendashlinked counterparts, with their performance maintained for \>20 days both in vitro and in vivo. The heat-treated films eliminate electrically insulating cross\textendashlinkers, resulting in a 3× increase in volumetric capacitance. Applying thermal energy using a focused femtosecond laser enables direct patterning of 3D PEDOT:PSS microstructures. The thermal treatment method is compatible with a wide range of substrates and is readily substituted into existing workflows for manufacturing devices, enabling its rapid adoption in the field of bioelectronics.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@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}

}

@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{doshi2024electrochemically,

title = {Electrochemically mutable soft metasurfaces},

author = {Siddharth Doshi and Anqi Ji and Ali I Mahdi and Scott T Keene and Skyler P Selvin and Philippe Lalanne and Eric A Appel and Nicholas A Melosh and Mark L Brongersma},

doi = {10.1038/s41563-024-02042-4},

year  = {2024},

date = {2024-11-13},

journal = {Nature Materials},

volume = {24},

issue = {2},

pages = {205-211},

abstract = {Active optical metasurfaces, capable of dynamically manipulating light in ultrathin form factors, enable novel interfaces between humans and technology. In such interfaces, soft materials bring many advantages based on their flexibility, compliance and large stimulus-driven responses. Here, we create electrochemically mutable, soft metasurfaces that capitalize on the swelling of soft conducting polymers to alter the shape and associated resonant response of metasurface elements. Such geometric tuning overcomes the typical trade-off between achieving substantial tuning and low optical loss that is intrinsic to dynamic metasurfaces relying on index tuning of materials. Using the commercial polymer PEDOT:PSS, we demonstrate dynamic, high-resolution colour tuning and high-diffraction-efficiency (\>19%) beam-steering devices that operate at CMOS-compatible voltages (~1.5 V). These results highlight how the deformability of soft materials can enable a class of high-performance metasurfaces that are suitable for body-worn technologies.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{hoang2024understanding,

title = {Understanding the Impact of Contact-Induced Strain on the Electrical Performance of Monolayer WS2 Transistors},

author = {Lauren Hoang and Marc Jaikissoon and \c{C}a\u{g}ıl K\"{o}ro\u{g}lu and Zhepeng Zhang and Robert KA Bennett and Jung-Hwan Song and Jerry A Yang and Jung-Soo Ko and Mark L Brongersma and Krishna C Saraswat and Eric Pop and Andrew J Mannix},

doi = {10.1021/acs.nanolett.4c02616},

year  = {2024},

date = {2024-10-04},

journal = {Nano Letters},

abstract = {Two-dimensional (2D) electronics require low contact resistance (RC) to approach their fundamental limits. WS2 is a promising 2D semiconductor that is often paired with Ni contacts, but their operation is not well understood considering the nonideal alignment between the Ni work function and the WS2 conduction band. Here, we investigate the effects of contact size on nanoscale monolayer WS2 transistors and uncover that Ni contacts impart stress, which affects the WS2 device performance. The strain applied to the WS2 depends on contact size, where long (1 μm) contacts (RC ≈ 1.7 kΩ·μm) show a 78% reduction in RC compared to shorter (0.1 μm) contacts (RC ≈ 7.8 kΩ·μm). We also find that thermal annealing can relax the WS2 strain in long-contact devices, increasing RC to 8.5 kΩ·μm. These results reveal that thermo-mechanical phenomena can significantly influence 2D semiconductor\textendashmetal contacts, presenting opportunities to optimize device performance through nanofabrication and thermal budget.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{ou2024achieving,

title = {Achieving optical transparency in live animals with absorbing molecules},

author = {Zihao Ou and Yi-Shiou Duh and Nicholas J Rommelfanger and Carl HC Keck and Shan Jiang and Kenneth Brinson Jr and Su Zhao and Elizabeth L Schmidt and Xiang Wu and Fan Yang and Betty Cai and Han Cui and Wei Qi and Shifu Wu and Adarsh Tantry and Richard Roth and Jun Ding and Xiaoke Chen and Julia A Kaltschmidt and Mark L Brongersma and Guosong Hong},

doi = {10.1126/science.adm6869},

year  = {2024},

date = {2024-09-06},

journal = {Science},

volume = {385},

issue = {6713},

pages = {eadm6869},

abstract = {Optical imaging plays a central role in biology and medicine but is hindered by light scattering in live tissue. We report the counterintuitive observation that strongly absorbing molecules can achieve optical transparency in live animals. We explored the physics behind this observation and found that when strongly absorbing molecules dissolve in water, they can modify the refractive index of the aqueous medium through the Kramers-Kronig relations to match that of high-index tissue components such as lipids. We have demonstrated that our straightforward approach can reversibly render a live mouse body transparent to allow visualization of a wide range of deep-seated structures and activities. This work suggests that the search for high-performance optical clearing agents should focus on strongly absorbing molecules.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{tertuliano2024high,

title = {High absorptivity nanotextured powders for additive manufacturing},

author = {Ottman A Tertuliano and Philip J DePond and Andrew C Lee and Jiho Hong and David Doan and Luc Capaldi and Mark Brongersma and X Wendy Gu and Manyalibo J Matthews and Wei Cai and Adrian J Lew},

doi = {10.1126/sciadv.adp0003},

year  = {2024},

date = {2024-09-04},

journal = {Science Advances},

volume = {10},

issue = {36},

pages = {eadp0003},

abstract = {The widespread application of metal additive manufacturing (AM) is limited by the ability to control the complex interactions between the energy source and the feedstock material. Here, we develop a generalizable process to introduce nanoscale grooves to the surface of metal powders which increases the powder absorptivity by up to 70% during laser powder bed fusion. Absorptivity enhancements in copper, copper-silver, and tungsten enable energy-efficient manufacturing, with printing of pure copper at relative densities up to 92% using laser energy densities as low as 83 joules per cubic millimeter. Simulations show that the enhanced powder absorptivity results from plasmon-enabled light concentration in nanoscale grooves combined with multiple scattering events. The approach taken here demonstrates a general method to enhance the absorptivity and printability of reflective and refractory metal powders by changing the surface morphology of the feedstock without altering its composition.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{kop2024ten,

title = {Ten principles for responsible quantum innovation},

author = {Mauritz Kop and Mateo Aboy and Eline De Jong and Urs Gasser and Timo Minssen and I Glenn Cohen and Mark Brongersma and Teresa Quintel and Luciano Floridi and Raymond Laflamme},

doi = {10.1088/2058-9565/ad3776},

year  = {2024},

date = {2024-04-22},

journal = {Quantum Science and Technology},

volume = {9},

issue = {3},

pages = {035013},

abstract = {This paper proposes a set of guiding principles for responsible quantum innovation. The principles are organized into three functional categories: safeguarding, engaging, and advancing (SEA), and are linked to central values in responsible research and innovation (RRI). Utilizing a global equity normative framework and literature-based methodology, we connect the quantum-SEA categories to promise and perils specific to quantum technology (QT). The paper operationalizes the responsible QT framework by proposing ten actionable principles to help address the risks, challenges, and opportunities associated with the entire suite of second-generation QTs, which includes the quantum computing, sensing, simulation, and networking domains. Each quantum domain has different technology readiness levels, risks, and affordances, with sensing and simulation arguably being closest to market entrance. Our proposal aims to catalyze a much-needed interdisciplinary effort within the quantum community to establish a foundation of quantum-specific and quantum-tailored principles for responsible quantum innovation. The overarching objective of this interdisciplinary effort is to steer the development and use of QT in a direction not only consistent with a values-based society but also a direction that contributes to addressing some of society's most pressing needs and goals.},

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{kuznetsov2024roadmap,

title = {Roadmap for Optical Metasurfaces},

author = {Arseniy I Kuznetsov and Mark L Brongersma and Jin Yao and Mu Ku Chen and Uriel Levy and Din Ping Tsai and Nikolay I Zheludev and Andrei Faraon and Amir Arbabi and Nanfang Yu and Debashis Chanda and Kenneth B Crozier and Alexander V Kildishev and Hao Wang and Joel KW Yang and Jason G Valentine and Patrice Genevet and Jonathan A Fan and Owen D Miller and Arka Majumdar and Johannes E Fr\"{o}ch and David Brady and Felix Heide and Ashok Veeraraghavan and Nader Engheta and Andrea Al\`{u} and Albert Polman and Harry A Atwater and Prachi Thureja and Ramon Paniagua-Dominguez and Son Tung Ha and Angela I Barreda and Jon A Schuller and Isabelle Staude and Gustavo Grinblat and Yuri Kivshar and Samuel Peana and Susanne F Yelin and Alexander Senichev and Vladimir M Shalaev and Soham Saha and Alexandra Boltasseva and Junsuk Rho and Dong Kyo Oh and Joohoon Kim and Junghyun Park and Robert Devlin and Ragip A Pala},

doi = {10.1021/acsphotonics.3c00457},

year  = {2024},

date = {2024-02-27},

journal = {ACS photonics},

volume = {11},

issue = {3},

pages = {816-865},

abstract = {Metasurfaces have recently risen to prominence in optical research, providing unique functionalities that can be used for imaging, beam forming, holography, polarimetry, and many more, while keeping device dimensions small. Despite the fact that a vast range of basic metasurface designs has already been thoroughly studied in the literature, the number of metasurface-related papers is still growing at a rapid pace, as metasurface research is now spreading to adjacent fields, including computational imaging, augmented and virtual reality, automotive, display, biosensing, nonlinear, quantum and topological optics, optical computing, and more. At the same time, the ability of metasurfaces to perform optical functions in much more compact optical systems has triggered strong and constantly growing interest from various industries that greatly benefit from the availability of miniaturized, highly functional, and efficient optical components that can be integrated in optoelectronic systems at low cost. This creates a truly unique opportunity for the field of metasurfaces to make both a scientific and an industrial impact. The goal of this Roadmap is to mark this “golden age” of metasurface research and define future directions to encourage scientists and engineers to drive research and development in the field of metasurfaces toward both scientific excellence and broad industrial adoption.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{doshi2024direct,

title = {Direct electron beam patterning of electro-optically active PEDOT: PSS},

author = {Siddharth Doshi and Dominik Ludescher and Julian Karst and Moritz Floess and Johan Carlstr\"{o}m and Bohan Li and Nofar Mintz Hemed and Yi-Shiou Duh and Nicholas A Melosh and Mario Hentschel and Mark Brongersma and Harald Giessen},

doi = {10.1515/nanoph-2023-0640},

year  = {2024},

date = {2024-01-04},

urldate = {2023-09-12},

journal = {Nanophotonics},

number = {0},

abstract = {The optical and electronic tunability of the conductive polymer poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) has enabled emerging applications as diverse as bioelectronics, flexible electronics, and micro- and nano-photonics. High-resolution spatial patterning of PEDOT:PSS opens up opportunities for novel active devices in a range of fields. However, typical lithographic processes require tedious indirect patterning and dry etch processes, while solution-processing methods such as ink-jet printing have limited spatial resolution. Here, we report a method for direct write nano-patterning of commercially available PEDOT:PSS through electron-beam induced solubility modulation. The written structures are water stable and maintain the conductivity as well as electrochemical and optical properties of PEDOT:PSS, highlighting the broad utility of our method. We demonstrate the potential of our strategy by preparing prototypical nano-wire structures with feature sizes down to 250 nm, an order of magnitude finer than previously reported direct write methods, opening the possibility of writing chip-scale microelectronic and optical devices. We finally use the high-resolution writing capabilities to fabricate electrically-switchable optical diffraction gratings. We show active switching in this archetypal system with \>95 % contrast at CMOS-compatible voltages of +2 V and −3 V, offering a route towards highly-miniaturized dynamic optoelectronic 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}

}

@article{sarkar2023physics,

title = {Physics‐Informed Machine Learning for Inverse Design of Optical Metamaterials},

author = {Sulagna Sarkar and Anqi Ji and Zachary Jermain and Robert Lipton and Mark L Brongersma and Kaushik Dayal and Hae Young Noh},

doi = {10.1002/adpr.202300158},

year  = {2023},

date = {2023-10-11},

urldate = {2023-10-11},

journal = {Advanced Photonics Research},

pages = {2300158},

abstract = {Optical metamaterials manipulate light through various confinement and scattering processes, offering unique advantages like high performance, small form factor and easy integration with semiconductor devices. However, designing metasurfaces with suitable optical responses for complex metamaterial systems remains challenging due to the exponentially growing computation cost and the ill-posed nature of inverse problems. To expedite the computation for the inverse design of metasurfaces, a physics-informed deep learning (DL) framework is used. A tandem DL architecture with physics-based learning is used to select designs that are scientifically consistent, have low error in design prediction, and accurate reconstruction of optical responses. The authors focus on the inverse design of a representative plasmonic device and consider the prediction of design for the optical response of a single wavelength incident or a spectrum of wavelength in the visible light range. The physics-based constraint is derived from solving the electromagnetic wave equations for a simplified homogenized model. The model converges with an accuracy up to 97% for inverse design prediction with the optical response for the visible light spectrum as input, and up to 96% for optical response of single wavelength of light as input, with optical response reconstruction accuracy of 99%.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{born2023off,

title = {Off-axis metasurfaces for folded flat optics},

author = {Brandon Born and Sung-Hoon Lee and Jung-Hwan Song and Jeong Yub Lee and Woong Ko and Mark L Brongersma},

doi = {10.1038/s41467-023-41123-x},

year  = {2023},

date = {2023-09-12},

urldate = {2023-09-12},

journal = {Nature Communications},

volume = {14},

issue = {1},

pages = {5602},

abstract = {The overall size of an optical system is limited by the volume of the components and the internal optical path length. To reach the limits of miniaturization, it is possible to reduce both component volume and path length by combining the concepts of metasurface flat optics and folded optics. In addition to their subwavelength component thickness, metasurfaces enable bending conventional folded geometries off axis beyond the law of reflection. However, designing metasurfaces for highly off-axis illumination with visible light in combination with a high numerical aperture is non-trivial. In this case, traditional designs with gradient metasurfaces exhibit low diffraction efficiencies and require the use of deep-subwavelength, high-index, and high-aspect-ratio semiconductor nanostructures that preclude inexpensive, large-area nanofabrication. Here, we describe a design approach that enables the use of low-index (n ≈ 1.5), low-aspect ratio structures for off-axis metagratings that can redirect and focus visible light (λ = 532 nm) with near-unity efficiency. We show that fabricated optical elements offer a very large angle-of-view (110°) and lend themselves to scalable fabrication by nano-imprint lithography.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}