Fig. 4: Second harmonic generation from a graded single ITO thin film.
From: Long-range optical coupling with epsilon-near-zero materials
a Measured shifted ENZ wavelength and intensity for a single-layer ITO thin film with thickness varied from d = 72 to 163 nm. b Modeled SHG emission from a single ITO layer with a thickness ranging from d = 70 to 170 nm. A uniform ENZ wavelength is set at λENZ = 1.2 µm in the modeling with incident angle θi = 5°. SHG curves were offset from top to bottom. c Measured SHG intensities at the doubled frequencies. The pump wavelength is λ = 1.2 µm (close to λENZ at d = 72 nm, black curve) with a power density of 636 W/cm2, and λ = 1.5 µm (close to λENZ at d = 163 nm, red curve) with a power density of 95 W/cm2, respectively, corresponding to the dashed lines in panel a.
