Fig. 3: Experimental demonstration of million-Q GMR at near-visible wavelengths.

a Left, Reflectance spectra of the device with P = 500 nm and L = 50 nm at \(\Gamma\) point (normal incidence). The Fano fitting (pink curve) reveals a Q factor of 1.10 million. The \(\Gamma\)-point data are extracted from extra-fine laser-scanning momentum-space-resolved reflectance spectroscopy with a wavelength resolution of ~0.42 pm/pixel and an angle resolution of ~0.028 ̊ /pixel; Right, the momentum-space-resolved spectra where the \(\Gamma\)-point data is extracted from. Note that a 0.28 ̊ range (10 pixels) of data are summed to broaden the ultranarrow mode linewidth for the convenience of visualization here, but only single-pixel data are used for Fano fittings. The same momentum-space-resolved spectra are plotted twice, one with the pink dashed lines highlighting the dispersion of GMR. The arrow points to the \(\Gamma\)-point resonance. b, c The same as (a) but for the devices with (b) L = 70 nm and (c) L = 90 nm. The fitted Q factors are 313 and 144 thousand respectively.