Fig. 1. (a) Top: (top left) Schematics of the silicon nanobars metasurface and (top right) its unit cell. Bottom: Calculated transmission spectrum of the metasurface with structural parameters , , . (b) Spherical multipolar structure of the metasurface. (c) Top: Cartesian ED and TD modes excitations. Bottom: The electric energy enhancement . It is defined as the electric energy inside the two nanobars normalized by the electric energy within the same volume of the nanobars for the pump field. (d) Electric near-field distributions at the resonance. Left: 3-D view. Right: top view.
Fig. 2. The architecture of the TN model, which consists of an inverse-design network connected to a pretrained forward model network. represents the input and output, which is the transmission spectra data in our case, and represents the output in the middle layer which is the structural parameters here.
Fig. 3. (a) Evolution of the training loss for the forward model network. (b) Comparison of the NN approximation to the real transmission spectrum. (c) Evolution of the training loss for the inverse-design model network. (d) Comparison of the spectra between the NN approximation and the input based on Eq. (2).
Fig. 4. Inverse design of Si nanobar metasurfaces with Fano-shape transmission spectra. (a)–(c) , 1500, and 1550 nm, respectively. , . (d)–(f) , , , 0.5, and 0.7, respectively. (g)–(i) , , 15, and 25 nm, respectively, .
Fig. 5. (a) SEM image of the fabricated sample with designed resonance at 1500 nm. (b) Experimentally measured linear spectra. (c) Experimentally measured THG spectra of the samples.
Fig. 6. (a)–(c) Optomechanic vibration under the -polarized pump. (a) Displacement of the nanobars after 1 ns. (b) The transient displacement and . (c) Spectral densities of displacement and . (d)–(f) Optomechanical vibration under the -polarized pump. (d) Displacement of the nanobars after 1 ns. (e) The transient displacement and . (f) Spectral densities of displacement and .
Fig. 7. The spectral density of in the (a) and (b) directions for different laser pump wavelengths.