JUNGHWAN SONG

All Publications

• Transfer Matrix Method-Compatible Model for Metamaterial Stacks ACS PHOTONICS Song, J., Lalanne, P., Seo, M., Brongersma, M. L. 2023

  View details for DOI 10.1021/acsphotonics.3c00693

  View details for Web of Science ID 001031276500001

• A Purcell-enabled monolayer semiconductor free-space optical modulator NATURE PHOTONICS Li, Q., Song, J., Xu, F., van de Groep, J., Hong, J., Daus, A., Lee, Y., Johnson, A. C., Pop, E., Liu, F., Brongersma, M. L. 2023

  View details for DOI 10.1038/s41566-023-01250-9

  View details for Web of Science ID 001031418200001

• Quantitative phase contrast imaging with a nonlocal angle-selective metasurface. Nature communications Ji, A., Song, J. H., Li, Q., Xu, F., Tsai, C. T., Tiberio, R. C., Cui, B., Lalanne, P., Kik, P. G., Miller, D. A., Brongersma, M. L. 2022; 13 (1): 7848

  Abstract

  Phase contrast microscopy has played a central role in the development of modern biology, geology, and nanotechnology. It can visualize the structure of translucent objects that remains hidden in regular optical microscopes. The optical layout of a phase contrast microscope is based on a 4 f image processing setup and has essentially remained unchanged since its invention by Zernike in the early 1930s. Here, we propose a conceptually new approach to phase contrast imaging that harnesses the non-local optical response of a guided-mode-resonator metasurface. We highlight its benefits and demonstrate the imaging of various phase objects, including biological cells, polymeric nanostructures, and transparent metasurfaces. Our results showcase that the addition of this non-local metasurface to a conventional microscope enables quantitative phase contrast imaging with a 0.02π phase accuracy. At a high level, this work adds to the growing body of research aimed at the use of metasurfaces for analog optical computing.

  View details for DOI 10.1038/s41467-022-34197-6

  View details for PubMedID 36543788

  View details for PubMedCentralID PMC9772391

• Metasurface optofluidics for dynamic control of light fields. Nature nanotechnology Li, Q., van de Groep, J., White, A. K., Song, J., Longwell, S. A., Fordyce, P. M., Quake, S. R., Kik, P. G., Brongersma, M. L. 2022

  Abstract

  The ability to manipulate light and liquids on integrated optofluidics chips has spurred a myriad of important developments in biology, medicine, chemistry and display technologies. Here we show how the convergence of optofluidics and metasurface optics can lead to conceptually new platforms for the dynamic control of light fields. We first demonstrate metasurface building blocks that display an extreme sensitivity in their scattering properties to their dielectric environment. These blocks are then used to create metasurface-based flat optics inside microfluidic channels where liquids with different refractive indices can be directed to manipulate their optical behaviour. We demonstrate the intensity and spectral tuning of metasurface colour pixels as well as on-demand optical elements. We finally demonstrate automated control in an integrated meta-optofluidic platform to open up new display functions. Combined with large-scale microfluidic integration, our dynamic-metasurface flat-optics platform could open up the possibility of dynamic display, imaging, holography and sensing applications.

  View details for DOI 10.1038/s41565-022-01197-y

  View details for PubMedID 36163507

• Non-local metasurfaces for spectrally decoupled wavefront manipulation and eye tracking. Nature nanotechnology Song, J., van de Groep, J., Kim, S. J., Brongersma, M. L. 2021

  Abstract

  Metasurface-based optical elements typically manipulate light waves by imparting space-variant changes in the amplitude and phase with a dense array of scattering nanostructures. The highly localized and low optical-quality-factor (Q) modes of nanostructures are beneficial for wavefront shaping as they afford quasi-local control over the electromagnetic fields. However, many emerging imaging, sensing, communication, display and nonlinear optics applications instead require flat, high-Q optical elements that provide substantial energy storage and a much higher degree of spectral control over the wavefront. Here, we demonstrate high-Q, non-local metasurfaces with atomically thin metasurface elements that offer notably enhanced light-matter interaction and fully decoupled optical functions at different wavelengths. We illustrate a possible use of such a flat optic in eye tracking for eyewear. Here, a metasurface patterned on a regular pair of eye glasses provides an unperturbed view of the world across the visible spectrum and redirects near-infrared light to a camera to allow imaging of the eye.

  View details for DOI 10.1038/s41565-021-00967-4

  View details for PubMedID 34594006

• Nanoelectromechanical modulation of a strongly-coupled plasmonic dimer. Nature communications Song, J., Raza, S., van de Groep, J., Kang, J., Li, Q., Kik, P. G., Brongersma, M. L. 2021; 12 (1): 48

  Abstract

  The ability of two nearly-touching plasmonic nanoparticles to squeeze light into a nanometer gap has provided a myriad of fundamental insights into light-matter interaction. In this work, we construct a nanoelectromechanical system (NEMS) that capitalizes on the unique, singular behavior that arises at sub-nanometer particle-spacings to create an electro-optical modulator. Using in situ electron energy loss spectroscopy in a transmission electron microscope, we map the spectral and spatial changes in the plasmonic modes as they hybridize and evolve from a weak to a strong coupling regime. In the strongly-coupled regime, we observe a very large mechanical tunability (~250meV/nm) of the bonding-dipole plasmon resonance of the dimer at ~1nm gap spacing, right before detrimental quantum effects set in. We leverage our findings to realize a prototype NEMS light-intensity modulator operating at ~10MHz and with a power consumption of only 4 fJ/bit.

  View details for DOI 10.1038/s41467-020-20273-2

  View details for PubMedID 33397929

• Direct laser writing of volumetric gradient index lenses and waveguides. Light, science & applications Ocier, C. R., Richards, C. A., Bacon-Brown, D. A., Ding, Q., Kumar, R., Garcia, T. J., van de Groep, J., Song, J., Cyphersmith, A. J., Rhode, A., Perry, A. N., Littlefield, A. J., Zhu, J., Xie, D., Gao, H., Messinger, J. F., Brongersma, M. L., Toussaint, K. C., Goddard, L. L., Braun, P. V. 2020; 9 (1): 196

  Abstract

  Direct laser writing (DLW) has been shown to render 3D polymeric optical components, including lenses, beam expanders, and mirrors, with submicrometer precision. However, these printed structures are limited to the refractive index and dispersive properties of the photopolymer. Here, we present the subsurface controllable refractive index via beam exposure (SCRIBE) method, a lithographic approach that enables the tuning of the refractive index over a range of greater than 0.3 by performing DLW inside photoresist-filled nanoporous silicon and silica scaffolds. Adjusting the laser exposure during printing enables 3D submicron control of the polymer infilling and thus the refractive index and chromatic dispersion. Combining SCRIBE's unprecedented index range and 3D writing accuracy has realized the world's smallest (15m diameter) spherical Luneburg lens operating at visible wavelengths. SCRIBE's ability to tune the chromatic dispersion alongside the refractive index was leveraged to render achromatic doublets in a single printing step, eliminating the need for multiple photoresins and writing sequences. SCRIBE also has the potential to form multicomponent optics by cascading optical elements within a scaffold. As a demonstration, stacked focusing structures that generate photonic nanojets were fabricated inside porous silicon. Finally, an all-pass ring resonator was coupled to a subsurface 3D waveguide. The measured quality factor of 4600 at 1550nm suggests the possibility of compact photonic systems with optical interconnects that traverse multiple planes. SCRIBE is uniquely suited for constructing such photonic integrated circuits due to its ability to integrate multiple optical components, including lenses and waveguides, without additional printed supports.

  View details for DOI 10.1038/s41377-020-00431-3

  View details for PubMedID 33298832

• High quality factor phase gradient metasurfaces. Nature nanotechnology Lawrence, M., Barton, D. R., Dixon, J., Song, J., van de Groep, J., Brongersma, M. L., Dionne, J. A. 2020

  Abstract

  Dielectric microcavities with quality factors (Q-factors) in the thousands to billions markedly enhance light-matter interactions, with applications spanning high-efficiency on-chip lasing, frequency comb generation and modulation and sensitive molecular detection. However, as the dimensions of dielectric cavities are reduced to subwavelength scales, their resonant modes begin to scatter light into many spatial channels. Such enhanced scattering is a powerful tool for light manipulation, but also leads to high radiative loss rates and commensurately low Q-factors, generally of order ten. Here, we describe and experimentally demonstrate a strategy for the generation of high Q-factor resonances in subwavelength-thick phase gradient metasurfaces. By including subtle structural perturbations in individual metasurface elements, resonances are created that weakly couple free-space light into otherwise bound and spatially localized modes. Our metasurface can achieve Q-factors >2,500 while beam steering light to particular directions. High-Q beam splitters are also demonstrated. With high-Q metasurfaces, the optical transfer function, near-field intensity and resonant line shape can all be rationally designed, providing a foundation for efficient, free-space-reconfigurable and nonlinear nanophotonics.

  View details for DOI 10.1038/s41565-020-0754-x

  View details for PubMedID 32807879