Lattice-core sandwich structure metamaterials are lightweight alternatives to monolithic materials that can present better mechanical, thermal, and energy dampening performance. Manufacturing lattice metamaterials to follow curved surfaces can pose a challenge, as the lattices rely on their geometric orientation to the substrate for their mechanical properties. This work rationally designed a lattice structure where the surface is broken up into “petals” connected to the underlying lattice, which localizes the petals’ impact response. This design opens a pathway for implementation of lattice-core sandwich structures onto complex surface geometries. These petal structures were evaluated for their energy absorption efficiency experimentally by utilizing pressure waves generated with nanosecond lasers and computationally via finite element modeling. The lattice structures exhibited a two-orders-of-magnitude decrease in transmitted pressure compared to their constituent steel at equivalent mass. Furthermore, localizing energy absorption into petal structures provided a 44% reduction in peak load compared to a continuous “single-petal” design.

Precise control of light–matter interactions at the nanoscale lies at the heart of nanophotonics. However, experimental examination at this length scale is challenging since the corresponding electromagnetic near-field is often confined within volumes below the resolution of conventional optical microscopy. In semiconductor nanophotonics, electromagnetic fields are further restricted within the confines of individual subwavelength resonators, limiting access to critical light–matter interactions in these structures. In this work, we demonstrate that photoelectron emission microscopy (PEEM) can be used for polarization-resolved near-field spectroscopy and imaging of electromagnetic resonances supported by broken-symmetry silicon metasurfaces. We find that the photoemission results, enabled through an in situ potassium surface layer, are consistent with full-wave simulations and far-field reflectance measurements across visible and near-infrared wavelengths. In addition, we uncover a polarization-dependent evolution of collective resonances near the metasurface array edge taking advantage of the far-field excitation and full-field imaging of PEEM. Here, we deduce that coupling between eight resonators or more establishes the collective excitations of this metasurface. All told, we demonstrate that the high-spatial resolution hyperspectral imaging and far-field illumination of PEEM can be leveraged for the metrology of collective, non-local, optical resonances in semiconductor nanophotonic structures.

The ability to dynamically steer sub-picosecond pulses from a monolithically integrated source is a critical milestone for the fields of nanophotonics and ultrafast optics. Reconfigurable dielectric metasurfaces have demonstrated the potential to exert dynamic control over the properties of light at sub-wavelength scales using spatial phase engineering. However, active manipulation of incoherent light sources remains a challenge, as current phase-sensitive metasurfaces developed for coherent sources cannot be directly applied. Here we theoretically predict and experimentally demonstrate sub-picosecond steering of ultrafast incoherent emission from a light-emitting metasurface over a 70° range. We utilize a monolithic III–V (GaAs) metasurface with embedded (InAs quantum dot) light sources positioned on a reflective Bragg (AlAs/Al0.3Ga0.7As) mirror to achieve a large optically induced phase change near the emission wavelength (1.25 μm). We use a spatial light modulator to structure a strong optical pump (800 nm) and project it onto the resonant metasurface to create reconfigurable spatial momentum profiles that dynamically steer the ultrafast (140 fs) quantum dot emission. Such dynamic spatiotemporal control of incoherent sources can enable new technologies for high-speed communications, holography and remote sensing. Researchers demonstrate sub-picosecond steering of ultrafast incoherent emission from a light-emitting metasurface. The steering is achieved over a 70° range.

We demonstrate a large and ultrafast reconfigurable circular dichroism arising from degenerate and tunable high-Q quasi-bound states-in-the-continuum resonances on a silicon metasurface using pump–probe spectroscopy.

In this letter we present a hierarchical unit cell incorporating a nonlinear energy sink (NES) that functions as a low-pass amplitude filter. The hierarchical unit cell is composed of an outer and inner mass coupled by essentially nonlinear springs. Other than its nonlinear coupling to the outer mass, the inner mass is otherwise unconstrained and thus acts as an NES. Using numerical simulations, we show that the nonlinear unit cell passively filters incident waves as a function of their amplitude. The resonator is inactive at low amplitudes, permitting waves to pass. At high amplitudes, the NES activates and its resonant behavior reflects incident waves. Consequently, the unit cell effectively operates as an amplitude limiter for specific signal frequency and amplitude ranges. Notably, the passing of low-amplitude incident energy while bypassing the nonlinearity results in very little distortion in transmitted signals. We analytically investigate this behavior further using a harmonic balance method. The analysis supports the transmission filtering behavior as well as the activation of the nonlinear energy sink. Lastly, we design and construct the nonlinear unit cell and perform tests using incident and transmitted waveguides composed of monatomic chains. Both the nonlinear unit cell and monatomic chains are assembled using steel masses and additively-manufactured springs. We test the fabricated filter using low and high amplitude signals and observe amplitude filtering at various excitation frequencies that document strong agreement with numerical simulations and the analytical model. The ability to passively reflect high amplitude waves, and transmit low amplitude waves with minimal distortion, may inspire new devices for hearing protection, or for isolating and protecting sensitive equipment and instruments.

We use photoemission electron microscopy for hyperspectral imaging of electromagnetic field localization in broken-symmetry III-V semiconductor metasurfaces with high selectivity to characterize complex resonant mode profiles, determine coherent interaction lengths, and corroborate FDTD simulations.

In this letter we propose a nonlinear hierarchical unit cell for use in passive, amplitude-dependent filtering of acoustic energy transmission. Analogous to unit cell designs which filter on frequency using bandgaps, the nonlinear hierarchical unit cell filters on amplitude with minimal waveform distortion. Numerical simulations of wave propagation in a mechanical chain employing the proposed unit cell predict nearly zero transmission of energy at low amplitudes, and nearly perfect energy transmission at large amplitudes. We hypothesize that the amplitude-dependent transmission behavior results from the nonlinear unit cell locking at high amplitudes, and thus acting as a single mass. When this single mass has the same weight as the other masses in the chain, near-perfect transmission is possible. We investigate this behavior further through a nonlinear analysis using a harmonic balance method to predict wave transmission through the nonlinear unit cell. The analysis confirms the transmission behavior and the rigid body hypothesis at large amplitudes. To validate the simulated and analysis results, we design and construct a monatomic chain using steel masses and additively-manufactured serpentine springs, to include a specially-designed nonlinear spring in the hierarchical unit cell. We then document amplitude-dependent filtering in the experiment for multiple frequencies, with strong agreement documented between measured results and simulation. In addition, high-speed camera images of the hierarchical cell verify the hypothesized locking behavior at large amplitudes. We believe the ability to passively select transmission based on a signal’s amplitude, with minimal resulting distortion, may open new opportunities in wave control and filtering, and new approaches for conceiving wave-based devices.

Metamaterials consisting of subwavelength resonators offer an exciting opportunity for realizing asymmetric transmission (AT) of linearly polarized light. However, to date, only moderate/narrow‐band AT responses have been obtained in metadevices based on stacked planar nanostructures. Here, leveraging a combination of a genetic algorithm (GA) based optimization method and a membrane projection lithography (MPL) fabrication approach, a quasi‐3D metamaterial for broadband AT of linearly polarized mid‐infrared light is demonstrated. Facilitated by the customized GA, an efficient exploration of 3D plasmonic meta‐atoms with broken mirror symmetry in the light propagation direction allows the satisfaction of the rigorous conditions for AT of linearly polarized waves over a broad wavelength range. Confirmed by surface current analysis, the observed AT behavior is attributed to the resonant coupling between the plasmonic nanostructures located on the two orthogonal walls of the MPL cavities. Incorporating an advanced inverse‐design method and a state‐of‐art fabrication technique, the methodology used in the present study provides a promising route for exploiting 3D metamaterials with sophisticated functionalities via effectively exploring the high‐dimensional parametric space offered by true 3D meta‐atoms.

We demonstrate ultrafast (<200 fs) unidirectional steering of photoluminescence over a 60° field of view from dielectric metasurfaces with embedded InAs quantum dots by creating a dynamical index grating using structured illumination.

In this work, we prove the existence of cascaded second-order nonlinearities in a dielectric metasurface by analyzing the second and third wave mixing signal in conjunction with crystal symmetry and polarization selection rules.

Enhancing the efficiency of second-harmonic generation using all-dielectric metasurfaces to date has mostly focused on electromagnetic engineering of optical modes in the meta-atom. Further advances in nonlinear conversion efficiencies can be gained by engineering the material nonlinearities at the nanoscale, however this cannot be achieved using conventional materials. Semiconductor heterostructures that support resonant nonlinearities using quantum engineered intersubband transitions can provide this new degree of freedom. By simultaneously optimizing the heterostructures and meta-atoms, we experimentally realize an all-dielectric polaritonic metasurface with a maximum second-harmonic generation power conversion factor of 0.5 mW/W2 and power conversion efficiencies of 0.015% at nominal pump intensities of 11 kW/cm2. These conversion efficiencies are higher than the record values reported to date in all-dielectric nonlinear metasurfaces but with 3 orders of magnitude lower pump power. Our results therefore open a new direction for designing efficient nonlinear all-dielectric metasurfaces for new classical and quantum light sources.

In this work, we investigate the linear optical response of a dielectric metasurface made of vertically-oriented germanium ellipses deposited on walls of a micron-scale cubic silicon nitride unit cell support matrix.

Optical metasurfaces were suggested as a route for engineering advanced light sources with tailored emission properties. In particular, they provide a control over the emission directionality, which is essential for single-photon sources and LED applications. Here, we experimentally study light emission from a metasurface composed of III-V semiconductor Mie-resonant nanocylinders with integrated quantum dots (QDs). Specifically, we focus on the manipulation of the directionality of spontaneous emission from the QDs due to excitation of different magnetic quadrupole resonances in the nanocylinders. To this end, we perform both back focal plane imaging and momentum-resolved spectroscopy measurements of the emission. This allows for a comprehensive analysis of the effect of the different resonant nanocylinder modes on the emission characteristics of the metasurface. Our results show that the emission directionality can be manipulated by an interplay of the excited quadrupolar nanocylinder modes with the metasurface lattice modes and provide important insights for the design of novel smart light sources and new display concepts.

We demonstrate microscopic control of optical nonlinearities in an intersubband polaritonic all-dielectric metasurface comprising of Mie resonators embedded with semiconductor heterostructures. Through heterostructure design, we control the polarity of the resonant χ (2) leading to suppression or enhancement of second-harmonic generation.

We design a resonant metasurface that uses Mie quadrupole modes to suppress the -1 diffraction order. We show that this suppression can be spectrally tuned using optical pumping on a picosecond timescale.