Time-variant metasurfaces enable tunable spectral bands of negative extinction

Abstract

We demonstrate that rapidly switched high-Q metasurfaces enable spectral regions of negative optical extinction.

Scattering from spheres made of time-varying and dispersive materials

“…Another interesting feature is that even some coupling between input and output frequencies of opposite sign can be observed. This may lead to interesting phenomena such as parametric amplification [73,74] and non-reciprocity [6]. Finally, we observe that for low input frequencies, the response of the sphere is weak, especially for larger multipolar orders, since in this case the optical size of the sphere is small.…”

Deep Optical Switching on Subpicosecond Timescales in an Amorphous Ge Metamaterial

“…As discussed previously, this behavior can be understood in the framework of coupled mode theory where the NIR pump pulse introduces time‐dependent losses in SAMs leading to an abrupt deterioration of the MIR mode's Q factor. [ 17 ] In other words, the MIR pulse excites the photonic mode of the system and within its radiative lifetime the refractive index of the a‐Ge metasurface is changed by the NIR pulse resulting in rapid damping of the mode. Thus, the transient lineshape of the MIR resonance exhibits spectral modulations characteristic for a Fourier transform of an abrupt change in field amplitude as a function of time.…”

“…Semiconductor‐based active metasurfaces (SAMs), on the other hand, offer a tunable electromagnetic response as their optical properties are an explicit function of time. [ 15–18 ] The tunability of SAMs can pave the way for various applications based on active control in photonic devices. [ 1 ]…”

Generation of even and odd high harmonics in resonant metasurfaces using single and multiple ultra-intense laser pulses

“…First, narrow-and moderate-bandgap semiconductors, with bandgap energies Δ that are not much larger than the laser photon energy ℏ , are damaged at moderate laser fluences due to multiphoton absorption followed by rapid free-carrier generation 15,16 . Moreover, the overabundance of free carriers can drastically reduce the quality ( ) factor of a resonant metasurface 17 , thereby defeating its key purpose: the creation of resonantly-driven optical hot spots. Second, harmonics absorption by opaque materials reduces the HHG-emitting volume and dramatically decreases the HHG efficiency 18 .…”

“…or dampen17 the metasurface resonance. As illustrated byFigure S1(see Supplementary Information Section 1 for the calculation of strong-field-induced FC generation), our choices of the metasurface material and laser wavelength = 2 / are strongly constrained if we are to access the non-perturbative regime of HHG in nanostructures.…”