Fig. 1. (a) Schematic of a four-layer GMRF; SEM images of the top and cross section for SiO2 thickness of 156.8 (b), (c), 193.2 (d), (e), 218.6 (f), (g), and 269.2 nm (h), (i).

Fig. 2. (a) Cross-sectional view of one period in the RSoft simulation. (b) The measured (M) and simulated (S) transmission spectra of the GMRF with two SiO2 film thicknesses. (c) The resonant wavelength as a function of SiO2 thickness for both the simulated and measured results.

Fig. 3. (a) Measured transmission spectra for different sucrose concentrations. (b) The resonant wavelength versus RI for the simulation and experimental results.

Fig. 4. (a) Simulated FWHM and Q factor as a function of the SiO2 thickness and (c) the simulated sensitivity and FOM as a function of the SiO2 thickness. (b) The experimental FWHM and Q factor as a function of the SiO2 thickness and (d) experimental sensitivity and FOM as a function of the SiO2 thickness.