Spatial dispersion in ZnP₂-D ₄ ⁸ has been studied. The spectral dependences of the refractive index n^c(Eǁc, kǁa), n^a(Eǁa, kǁc) and n^b(Eǁb, kǁc) had been determined. It was shown that the dispersion is positive n^c(Eǁc, kǁa), n^a(Eǁa, kǁc) > n^b(Eǁb, kǁc) in λ > λ₀ region, the dispersion is negative n^c(Eǁc, kǁa) at λ < λ₀, and Δn = n^c – n^b= 0 at λ = λ₀. The LIV characteristics of Me-ZnP₂-D ₄ ⁸ diodes had been studied at different temperatures, the temperature dependences of the “imperfection” factor δ for different Schottky barriers. Capacitance voltage characteristics of Me-ZnP₂-D ₄ ⁸ photodiodes obtained by electrochemical deposition of metal and by thermo-chemical spraying in vacuum had been studied. The influence of birefringence and gyration on spectral characteristics of p-n photodiodes and Schottky diodes had been revealed. The ability of controlling photodiodes’ characteristics was obtained using the gyration particularities in ZnP₂-D ₄ ⁸ crystals.