Reflective spectra had been researched in In0.3Ga0.7As quantum layers, modulated by the reflection and transmittance wavelength at P, P (S, S) and 45°, 45° (135°, 135°) light-wave polarizations at an incident angle near to the normal and Brewster ones. Isotropic wavelengths λ₀ - 1.137 μm (1.09 eV), λ₀₂ - 1.11 μm (1.12 eV) and λ₀₃ – 0.932 μm (1.09 eV) had been revealed. The refractive indexes n for P, P (S, S) and 45°, 45° (135°, 135°) were intersecting for these wavelengths and theirs difference Δn = nPP - nSS (Δn = n(45°) - n(135°)) intersects the null axis. The isotropic wavelength (λ₀) was shifted towards the long wavelength region at Brewster angle in reference to the case of perpendicular incidence of light (φ = 7°) on the QW surface.