Low-Power Absorption Saturation in Semiconductor Metasurfaces

Abstract

Saturable optical elements lie at the cornerstone of many modern optical systems. Regularly patterned quasi-planar nanostructuresmetasurfacesare known to facilitate nonlinear optical processes. Such subwavelength semiconductor nanostructures can potentially serve as saturable components. Here we report on the intensity-dependent reflectance of femtosecond laser pulses from semiconductor metasurfaces with Mie-type modes, caused by the absorption saturation. Arrays of GaAs nanocylinders with magnetic dipole resonances in the spectral vicinity of the GaAs bandgap demonstrate a reduced saturation intensity and increased selfmodulation efficiency, an order of magnitude higher than bulk GaAs or unstructured GaAs films. By contrast, the reflection modulation is shown to be negligible in the CW regime for the same average intensities, indicating that the process is not the result of temperature effects. Our work provides a novel idea for low-power saturable elements based on nonthermal nature of saturation. We conclude by devising a high-quality metasurface that can be used, in theory, to further reduce the saturation fluence below 50 nJ/cm 2 .

Metasurface Integrated Monolayer Exciton Polariton

“…Another promising platform will be subwavelength patterned surfaces, also known as dielectric metasurfaces . These metasurfaces can shape the optical wavefront using the subwavelength scatterers, also known as meta-atoms, and have recently been used to drastically miniaturize imaging and sensing devices, − as well as to enhance light–matter interaction. , This nanopatterned, periodic photonic lattice supports a rich cluster of optical Bloch mode and can tightly confine the electromagnetic field. , Moreover, computational design and dispersion engineering of the meta-atoms allow unprecedented nanophotonic engineering. − Going beyond passive metasurfaces, researchers are now exploring new materials to create active metasurfaces. , In fact, nonlinear frequency conversion has been reported with the GaSe integrated silicon metasurface . EP has also been demonstrated on a TMD-clad one-dimensional (1D) grating structure .…”

“…34−36 Going beyond passive metasurfaces, researchers are now exploring new materials to create active metasurfaces. 37,38 In fact, nonlinear frequency conversion has been reported with the GaSe integrated silicon metasurface. 39 EP has also been demonstrated on a TMD-clad one-dimensional (1D) grating structure.…”

Construction of New Azo‐group Containing Polycyclic Imidazole Derivatives: Computational Mechanistic, Structural, and Fluorescence Studies

“…[19] Previous studies showed that experimentally defined band gap and theoretically calculated HOMO-LUMO energy gap might not be consistent. [20] The HOMO and LUMO energy difference (2.41 eV), and theoretical fundamental energy gap (band gap) studies (total energy differences between N À 1-electron, N-electron, N + 1 electron states, See SI) shows that the compounds can be employed as an alternative of commercially available semiconducting materials (e. g. GaAs/1.42 eV, [21] CdTe/1.45 eV [22] ). Relative quantum yield (QY) calculation was performed experimentally according to the literature recommendations.…”

Externally driven nonlinear time-variant metasurfaces

“…31,32 Using high-Q structures, photonic devices with properties beyond what is available with bulk materials and low-Q metasurfaces can be attained. [33][34][35] High-index semiconductor metasurfaces with specially designed high-Q resonances have great capability for enhanced nonlinear effects and other benefits for creating various compact nonlinear photonics devices.…”