Fig. 4. Transmittance versus wavelength of the proposed sensor when the defect layer with a thickness of 1.20 μm 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 angle of incidence of radiation is 10° (a), 20° (b), 30° (c) 45° (d), 60° (e).