Since SrTiO₃ is energetic compound of optical electronic devices, we examine result Ag doping with SrTiO₃lattice. Properties of optical such as reflectivity, absorption, refractive index (n), refractive index (k), loss function, real part and imaginary part of dielectric function and real part of conductivity describe how light interact with matter. Firstly, we calculated these optical properties of pure SrTiO₃ compound and after this we compare the optical properties with Ag doped SrTiO3 compound shown in Fig 4. We analysis that these optical properties are frequency dependent and interconnected.

Ag doped SrTiO₃, all points where the absorption is lowest, the reflection Fig 4(b) is found to be maximum. Here we analyze that the presence of doping slightly changes the absorption spectra.

As shown in Fig 4(e & f) the dielectric function is divided into two parts: First is real part and second is imaginary part. The real part of dielectric function (DF) represents polarization, while the imaginary part describes energy dissipation within the framework. In the case of a pure SrTiO₃, the imaginary component of DF is 0 at 0 electron Volt. It illustrates that energy dissipation (absorption) is zero inside the SrTiO_3. If we compare this value with the Ag-doped SrTiO₃ we observe that energy dissipation is present at 0 electron Volt. The imaginary part of DF shows four highest peaks which observed at 4.12, 7.28, 23.02 and 36.33 electron Volt of pure SrTiO₃, which relates the 4 absorption peaks depicted in Fig 4(a). Ag-doped SrTiO₃ shows notable peak at 8.69eV and absorption peak at 23.80 electron Volt is slightly decreases for doped SrTiO₃. It can be observed Ag-doped SrTiO₃ system indicates do not a change in absorption peaks from high energy to low energy, but also a transfer in absorption peaks away from high energy. The energy area in which electrons do not generally bound to their lattice positions and conduct plasma oscillations upon light exposure defined as the maximum loss function. In comparison to the pure SrTiO₃, we analyze that the Ag-doped SrTiO₃ a high peak of plasma oscillation has shifted to smaller energies. Fig 4(d) shows that the energy loss function of doped SrTiO₃ reaches its maximum value as compare to pure system of the dielectric function. The both parts of refractive index (n & k), which based on energy (frequency), make complex refractive index shown in Fig 4(g & h). The doped system’s refractive index (n) is estimated to be 3.23eV, which is significantly higher than the pure system’s (2.50 eV). After Ag addition, the refractive index (n) of semiconducting SrTiO₃ shifts to higher values, confirming the transition of semiconducting SrTiO₃ to metallic material. The lowest absorption energy is correlated with highest refractive index value at zero photon energy. The refractive index decreases as absorption increases, as seen in Fig 4(g). The annihilation of energy in the system defined be with extinction coefficient, which correlated by the absorption spectrum. At photon energy is 1.3eV, the extinction coefficient of pure SrTiO₃ is zero, which is the same as its indirect band gap and until 1.3eV, there is no extinction of energy inside the substance. So, that it has zero absorption. The refractive index (n) rises in parallel by absorption. The refractive index (k) of Ag-doped SrTiO₃ has transferred to a lower energy, with sharp peaks occurring at about 4.40eV, 8.50eV, 19.65 eV, 23.68eV and 36.41eV [19-21].