Comparison of measurement results of MgF2–Nb2O5 distributed Bragg reflectors with different periods

In this study, by using the Corning 1737 glass as a substrate and an e-beam system, the optical properties of the deposit MgF2 and Nb2O5 single-layer film were investigated in terms of extinction coefficients ( k values) and refractive indices ( n values). The equation d = λ /(4 n ) was used to calculate the thickness ( d ) of 1/4 wavelength ( λ ) for each layer of MgF2 and Nb2O5 layer in the MgF2–Nb2O5 bilayer films of the designed distributed Bragg reflectors (DBRs) with a reflective wavelength at blue light ( ∼ 450 nm). Each pair of MgF2–Nb2O5 bilayer film was defined as a period, and the glass substrates were used to deposit the films with two, four, and six periods for the fabrication of the DBRs. The field emission scanning electron microscope equipped with a focused ion beam was used to measure the thickness of each MgF2–Nb2O5 layer in the DBRs with different periods. The measured maximum reflective ratios were compared with Sheppard’s approximate equation, which calculates only the maximum reflective ratio at a specific wavelength. We would show that the measured results of the fabricated DBRs matched the results simulated using Sheppard’s approximate equation.