We report on the evaluation of optical characteristics of three media (3M) optical thin films due to enhancement of refractive indices of growth material and incident angle of light to the air-film interface by theoretical analysis and then simulation using Matlab. It has been found that optical performance characteristics, transmittance and reflectance as a function of wavelength of 3M film structure are noticeably influenced with increasing incident angle of light at the air-film interface, and refractive indices of film material and substrate. In particular, frequency or periodicity of reflected spectra is found to have distinct values with increasing incident angle from 5 to 40 degree while the device is in operation. Opposite tendency is observed in transmitted spectra. The dissimilar refractive indices of film affect moderately on the reflectance and transmittance of optical thin film. On the other hand, the reflectance decreases significantly, and oppositely transmittance improves drastically with increasing refractive index of substrate. The proposed research work in this study would be very helpful to develop nano-coating technology to determine best film-substrate materials having desired refractive indices, at a specified incident angle of light for particular application in the third-generation optical devices.