Fig. 3. Transmittance versus wavelength at normal incidence of the proposed PC when the defect layer is filled with milk samples with different refractive indices, n, of 1.0 (red), 1.3483 (blue), 1.35012 (brown), 1.3525 (Niagara dark orchid), 1.35692 (black) and 1.36541 (steel blue). The defect layer thickness is 1.00 μm (a), 1.05 μm (b), 1.10 μm (c) and 1.20 μm (d).