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=lambda/(4n) was used to calculate the thickness (d) of 1/4 wavelength (lambda) 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 (similar to 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.