Fig. 4: The nonlinear emissions from the Si metasurface and power dependence between input power and nonlinear emissions.
From: Broadband infrared imaging governed by guided-mode resonance in dielectric metasurfaces
a–c The measured FWM and THG emission spectra from Si metasurface while tuning the signal wavelength (λs) when fixing the pump wavelength λp = 1130 nm. The tuning ranges of the signal wavelength are (a) from 1350 to 1500 nm, (b) from 1500 to 1900 nm, and (c) from 2300 to 4700 nm. d The measured FWM emission spectra from Si metasurface while tuning the pump wavelength (λp) from 1080 nm to 1140 nm. The signal beam wavelength is fixed at λs = 2250 nm. The relation between the frequencies of FWM emissions, signal frequency, and pump frequency can be expressed as: ωFWMp = 2ωpump + ωsignal, ωFWMs = ωpump + 2ωsignal, and ω’FWMp = 2ωpump − ωsignal. The THG emission is generated by the signal beam (ωTHG = 3ωsignal). The color indicates the perceived color of human eye for the wavelength range 380 − 780 nm. e, f The quadratic and linear power dependence of pump beam (a) and signal beam (b) on the two FWM processes (ωFWMp = 2ωpump + ωsignal and ωFWMs = ωpump + 2ωsignal) with experimental data and fitting curves
