## About Us

We are dedicated to multidisciplinary research in the area of wave-matter interaction from microwaves to optics. Grounded on the fundamental physical principles, and the on-demand dimensionality of materials and nanomaterials, we address tantalizing experimental and theoretical physical questions in the fields of nanophotonics, plasmonics, and metamaterials applicable to global energy, defense, and health challenges.

## Featured

## Plasmonic topological metasurface by encircling an exceptional point

Resonant scattering, guided mode propagation phase, and/or orientation-dependent phase retardations are the three main mechanisms used to date to conceive optical metasurfaces. Here, we introduce an additional degree of freedom to address optical phase engineering by exploiting the topological features of non-Hermitian matrices operating near their singular points. Choosing metasurface building blocks to encircle a singularity following an arbitrarily closed trajectory in parameter space, we engineered a topologically protected full 2π-phase on a specific reflected polarization channel. The ease of implementation together with its compatibility with other phase-addressing mechanisms bring topological properties into the realm of industrial applications at optical frequencies and prove that metasurface technology represents a convenient test bench to study and validate topological photonic concepts.

## Photonic quantum Hall effect and multiplexed light sources of large orbital angular momenta

The quantum Hall effect involves electrons confined to a two-dimensional plane subject to a perpendicular magnetic field, but it also has a photonic analogue. Using heterostructures based on structured semiconductors on a magnetic substrate, we introduce compact and integrated coherent light sources of large orbital angular momenta based on the photonic quantum Hall effect. The photonic quantum Hall effect enables the direct and integrated generation of coherent orbital angular momenta beams of large quantum numbers from light travelling in leaky circular orbits at the interface between two topologically dissimilar photonic structures. Our work gives direct access to the infinite number of orbital angular momenta basis elements and will thus enable multiplexed quantum light sources for communication and imaging applications.

## Experimental demonstration of single-mode topological valley-Hall lasing at telecommunication wavelength.

Topology plays a fundamental role in contemporary physics and enables new information processing schemes and wave device physics with built-in robustness. However, the creation of photonic topological phases usually requires complex geometries that limit the prospect for miniaturization and integration and dispossess designers of additional degrees of freedom needed to control topological modes on-chip. By controlling the degree of asymmetry (DoA) in a photonic crystal with broken inversion symmetry, we report single-mode lasing of valley-Hall ring cavities at telecommunication wavelength. Our results open the door to novel optoelectronic devices and systems based on compact topological integrated circuits.

## Octave bandwidth photonic fishnet-achromatic-metalens

Planar structured interfaces, also known as metasurfaces, are continuously attracting interest owing to their ability to manipulate fundamental attributes of light, including angular momentum, phase, or polarization. However, chromatic aberration, limiting broadband operation, has remained a challenge for metasurfaces-based optical components and imagers. Here we report and experimentally demonstrate polarization-independent fishnet-achromatic-metalenses with measured average efficiencies over 70% in the continuous band from the visible (640 nm) to the infrared (1200 nm). Results of the scalable platform are enabling for applications requiring broad bandwidth and high efficiency including energy harvesting, virtual reality and information processing devices, or medical imaging.

## Symmetry-breaking-induced plasmonic exceptional points and nanoscale sensing

Singularities of open systems, known as exceptional points (EPs), have been shown to exhibit increased sensitivities, but the observation of EPs has so far been limited to wavelength-scaled systems subject to the diffraction limit. We propose a novel approach to EPs based on spatial symmetry breaking and report their observation in plasmonics at room temperature. Their utility as sensors of anti-immunoglobulin G, the most abundant immunoglobulin isotype in human serum, is evaluated. Our work opens the way to a new class of nanoscale devices, sensors and imagers based on topological polaritonic effects.

## Nonreciprocal lasing in topological cavities of arbitrary geometries

Resonant cavities that confine light are crucial components of lasers. Typically, these cavities are designed to high specification to get the best possible output. That, however, can limit their integration into photonic devices and optical circuits. The confinement of light to topologically protected edge states can result in unidirectional propagation and confinement over arbitrary geometries. Relaxing the resonant cavity design criteria should be useful in designing photonic devices.

## Lasing action from photonic bound states in continuum

In 1929, only three years after the advent of quantum mechanics, von Neumann and Wigner showed that Schrödinger’s equation can have bound states above the continuum threshold. These peculiar states, called bound states in the continuum (BICs), manifest themselves as resonances that do not decay. Here we report, at room temperature, lasing action from an optically pumped BIC cavity. BIC lasers open up new avenues in the study of light–matter interaction because they are intrinsically connected to topological charges and represent natural vector beam sources which are highly sought after in the fields of optical trapping, biological sensing and quantum information.

## Research

## Recent Publications

- W. Redjem, B. Kanté et. al., “Defect engineering of silicon with ion pulses from laser acceleration,” arXiv prepring arxiv:2203.13781 (2022).
- T. Schenkel, W. Redjem, A. Persaud, W. Liu, PA Seidl, AJ Amsellem, B. Kanté, and Q. Ji, “Exploration of Defect Dynamics and Color Center Qubit Synthesis with Pulsed Ion Beams,” Quantum Beam Sci.,
**6**(1), 13 (2022). - Q. Song, M. Odeh, J. Zúñiga-Pérez, B. Kanté, and P. Genevet, “Plasmonic topological metasurface by encircling an exceptional point,” Science,
**373**(6559), 1133–1137 (2021). - B. Bahari, L. Hsu, S. H. Pan, D. Preece, A. Ndao, A. El Amili, Y. Fainman, and B. Kanté, “Photonic quantum Hall effect and multiplexed light sources of large orbital angular momenta,” Nature Physics (2021).
- M. Odeh, M. Dupré, K. Kim, and B. Kanté, “Optical response of jammed rectangular nanostructures,” Nanophotonics
**10**(1) 705–711 (2021). - W. Noh*, H. Nasari*, H.-M. Kim*, Q. Le-Van, Z. Jia, C.-H. Huang, and B. Kanté, “
__Experimental demonstration of single-mode topological valley-Hall lasing at telecommunication wavelength controlled by the degree of asymmetry__,” Optics Letters**45**(15) 4108–4111 (2020). - A. Ndao, L. Hsu, J. Ha, J. Park, C. Chang-Hasnain, and B. Kanté, “
__Octave bandwidth photonic fishnet-achromatic-metalens__,” Nature Communications**11**, 3205 (2020). - R. Contractor, W. Noh, Q. Le-Van, and B. Kanté, “
__Doping-induced plateau of strong electromagnetic confinement in the momentum space__,” Optics Letters**45**(13) 3653–3656 (2020). - A. Ndao, L. Hsu, W. Cai, J. Ha, J. Park, R. Contractor, Y. Lo, and B. Kanté, “Differentiating and quantifying exosome secretion from a single cell using quasi-bound states in the continuum,” Nanophotonics
**9**(5) 20200008 (2020).