Search results for "metasurface"
showing 10 items of 17 documents
Finite-Size and Illumination Conditions Effects in All-Dielectric Metasurfaces
2022
Dielectric metasurfaces have emerged as a promising alternative to their plasmonic counterparts due to lower ohmic losses, which hinder sensing applications and nonlinear frequency conversion, and their larger flexibility to shape the emission pattern in the visible regime. To date, the computational cost of full-wave numerical simulations has forced the exploitation of the Floquet theorem, which implies infinitely periodic structures, in designing such devices. In this work, we show the potential pitfalls of this approach when considering finite-size metasurfaces and beam-like illumination conditions, in contrast to the typical infinite plane-wave illumination compatible with the Floquet t…
Third-harmonic light polarization control in magnetically resonant silicon metasurfaces
2021
Nonlinear metasurfaces have become prominent tools for controlling and engineering light at the nanoscale. Usually, the polarization of the total generated third harmonic is studied. However, diffraction orders may present different polarizations. Here, we design an high quality factor silicon metasurface for third harmonic generation and perform back focal plane imaging of the diffraction orders, which present a rich variety of polarization states. Our results demonstrate the possibility of tailoring the polarization of the generated nonlinear diffraction orders paving the way to a higher degree of wavefront control.
Harmonic generation in all-dielectric metasurfaces
2023
Nonlinear light generation is a key phenomenon in many optical systems. Recently, the field of nonlinear optics has moved to the miniaturization of conventional bulky components. Among all the new platforms that have been proposed, dielectric nanoscale resonators represent excellent candidates for light generation and manipulation. When arranged in periodic arrays, such high refractive index scattering components become an artificial material called metasurface. Several approaches for designing platforms with enhanced optical nonlinearities at moderate pump intensities have been proposed. In this chapter, we review the most recent results on second- and third-order nonlinear processes in hi…
High Quality Factor Silicon Membrane Metasurface for Intensity-Based Refractive Index Sensing
2021
We propose a new sensing device based on all-optical nano-objects placed in a suspended periodic array. We demonstrate that the intensity-based sensing mechanism can measure environment refractive index change of the order of 1.8×10−6, which is close to record efficiencies in plasmonic devices.
Opto-thermally controlled beam steering in nonlinear all-dielectric metastructures
2021
Reconfigurable metasurfaces have recently gained a lot of attention in applications such as adaptive meta-lenses, hyperspectral imaging and optical modulation. This kind of metastructure can be obtained by an external control signal, enabling us to dynamically manipulate the electromagnetic radiation. Here, we theoretically propose an AlGaAs device to control the second harmonic generation (SHG) emission at nanoscale upon optimized optical heating. The asymmetric shape of the used meta-atom is selected to guarantee a predominant second harmonic (SH) emission towards the normal direction. The proposed structure is concurrently excited by a pump beam at a fundamental wavelength of 1540 nm and…
Photonic controlled metasurface for intelligent antenna beam steering applications including 6G mobile communication systems
2023
This paper presents a novel metasurface antenna whose radiation characteristics can be remotely controlled by optical means using PIN photodiodes. The proposed reconfigurable antenna is implemented using a single radiating element to minimize the size and complexity. The antenna is shown to exhibit a large impedance bandwidth and is capable of radiating energy in a specified direction. The proposed antenna consists of a standard rectangular patch on which is embedded an H-tree shaped fractal slot of order 3. The fractal slot is used to effectively reduce the physical size of the patch by 75 % and to enhance its impedance bandwidth. A metasurface layer is strategically placed above the patch…
Rotational Doppler Frequency Shift from Time‐Evolving High‐Order Pancharatnam–Berry Phase: A Metasurface Approach
2021
The Doppler frequency shift of sound or electromagnetic waves has been widely investigated in many different contexts and, nowadays, represents a formidable tool in medicine, engineering, astrophysics, and optics. Such effect is commonly described in the framework of the universal energy-momentum conservation law. In particular, the rotational Doppler effect has been recently demonstrated using light carrying orbital angular momentum. When a wave undergoes a cyclic adiabatic transformation of its Hamiltonian, it is known to acquire the so-called Pancharatnam–Berry (PB) phase. In this work, an experimental evidence of the direct connection between the high-order PB phase time evolution on th…
Tailoring Third-Harmonic Diffraction Efficiency by Hybrid Modes in High-Q Metasurfaces
2021
Metasurfaces are versatile tools for manipulating light; however, they have received little attention as devices for the efficient control of nonlinearly diffracted light. Here, we demonstrate nonlinear wavefront control through third-harmonic generation (THG) beaming into diffraction orders with efficiency tuned by excitation of hybrid Mie-quasi-bound states in the continuum (BIC) modes in a silicon metasurface. Simultaneous excitation of the high-Q collective Mie-type modes and quasi-BIC modes leads to their hybridization and results in a local electric field redistribution. We probe the hybrid mode by measuring far-field patterns of THG and observe the strong switching between (0,-1) and…
Reconfigurable nonlinear response of dielectric and semiconductor metasurfaces
2021
Abstract Optically resonant dielectric and semiconductor metasurfaces are an emerging and promising area of nanophotonics and light–matter interaction at the nanoscale. Recently, active tuning of the linear response and nonlinear effects of these components has received an increasing amount of interest. However, so far these research directions have remained separated with only few sporadic works that study their combination beginning to appear in the literature. The evolution of nonlinear metasurfaces based on dielectric and semiconductor materials toward reconfigurable and dynamic components could potentially answer the demand of integrated on-chip components that realize essential functi…
Transient guided-mode resonance metasurfaces with phase-transition materials
2023
We investigate transient, photo-thermally induced metasurface effects in a planar thin-film multilayer based on a phase-transition material. Illumination of a properly designed multilayer with two obliquely incident and phase-coherent pulsed pumps induces a transient and reversible temperature pattern in the phase-transition layer. The deep periodic modulation of the refractive index, caused by the interfering pumps, produces a transient Fano-like spectral feature associated with a guided-mode resonance. A coupled opto-thermal model is employed to analyze the temporal dynamics of the transient metasurface and to evaluate its speed and modulation capabilities. Using near-infrared pump pulses…