Light Emission from Self‐Assembled and Laser‐Crystallized Chalcogenide Metasurface

Abstract

demonstrated to improve the light emission efficiency through enhancing light outcoupling efficiency [1,2] and spontaneous emission rate. [3][4][5] Nanophotonic engineering can lead to narrowband and directive light emission. [6][7][8] Chalcogenide materials with unique phase change properties have been explored for tunable thermal emission [9] or reflection [10] in infrared wavelength ranges. PhC waveguide has been demonstrated on thin-film chalcogenide by e-beam lithography, showing slow light and resonance-enhanced parametric nonlinear process in material. [11,12] To reduce cost and improve scalability, solution-processed chalcogenide nanostructure is recently reported through solution process and self-assembling. [13] In this work, we demonstrate the first active chalcogenide metasurface fabricated by self-assembling with tunable dimensions. The nanophotonic structure is tailored to enhance the light emission efficiency through resonance-enhanced absorption of excitation, suppressing guided mode at emission wavelength and Purcell enhancement. [14][15][16][17] The 2D hexagonal chalcogenide nanorod arrays are self-assembled [13] on a silicon template through solution processing. [18][19][20][21][22][23][24] Silicon nanophotonic structure with a few nanometer surface roughness enables delamination of top and bottom bulk chalcogenides during solvent evaporation leaving only a filled nanorod array. Nanophotonic confinement can simultaneously manifest local photon density for enhanced Subwavelength periodic confinement can collectively and selectively enhance local light intensity and enable control over the photoinduced phase transformations at the nanometer scale. Standard nanofabrication process can result in geometrical and compositional inhomogeneities in optical phase change materials, especially chalcogenides, as those materials exhibit poor chemical and thermal stability. Here the self-assembled planar chalcogenide nanostructured array is demonstrated with resonance-enhanced light emission to create an all-dielectric optical metasurface, by taking advantage of the fluid properties associated with solution-processed films. A patterned silicon membrane serves as a template for shaping the chalcogenide metasurface structure. Solution-processed arsenic sulfide metasurface structures are self-assembled in the suspended 250 nm silicon membrane templates. The periodic nanostructure dramatically manifests the local lightmatter interaction such as absorption of incident photons, Raman emission, and photoluminescence. Also, the thermal distribution is modified by the boundaries and thus the photothermal crystallization process, leading to the formation of anisotropic nanoemitters within the field enhancement area. This hybrid structure shows wavelength-selective anisotropic photoluminescence, which is a characteristic behavior of the collective response of the resonantguided modes in a periodic nanostructure. The resonance-enhanced Purcell effect can manifest the quantum efficiency of localized light emission.

Uniform Huygens Metasurfaces with Postfabrication Phase Pattern Recording Functionality

“…Figure 4d shows the associated measured far-field intensity producing a guitar-shaped profile, confirming that the recorded amplitude pattern was converted into the same phase pattern. The advantage of this approach is that uniform metasurfaces can be fabricated with such mass-production techniques as nanoimprint, 51,52 while the functionality can be recorded aposteriori using digital optics tools such as a spatial light modulator (SLM). 53 In addition, the phase distribution recording system could be combined with an in situ optical control, which allows real-time monitoring of the phase element manufacturing process.…”

Integrated Photonic Convolutional Neural Network Based on Silicon Metalines

“…For instance, phase change materials with a high refractive index contrast can fill those slots and offer sufficient phase tenability [36] for a fully programmable metasystem. Some active materials demonstrate highly nonlinear responses (like two-photon absorption-related free carrier absorption or absorption saturation) and are transparent at telecommunication wavelength ranges; these materials can be utilized as nano-scale activation functions in diffractive networks with solution processing [37], [38].…”

Integrated photonic metasystem for image classifications at telecommunication wavelength

“…For example, phase change materials with high refractive index contrast can fill those slots and provide sufficient phase tunability 52 for a fully reprogrammable metasystem. Certain active materials exhibit exceptionally high nonlinear responses (such as two-photon absorption-related free carrier absorption or absorption saturation) and are transparent at telecommunication wavelength ranges, which can be integrated into the diffractive networks as nano-scale activation functions with solution processing 53 , 54 .…”