Design and manufacture of a bandpass filter with high transmittance and steep edge on both sides

By using Nb 2 O 5 and SiO 2 as the coating material, a 152 layers (12 cavities) bandpass film stack with steep edge on both sides was designed. Multiple thickness control methods, including direct optical monitoring control and time control were used in coating strategy. To confirm the feasibility of this coating strategy, a process simulation was performed using Simulator software, and the simulation result indicated that relative thickness errors for all layers were less than ±0.1%. A bandpass filter with this film stack on one side was manufactured by using a plasma assisted reactive magnetic sputtering coating machine. The measuring result shows that the peak transmittance of the filter (without AR on backside) is up to 95.4%, and the steepness of both blocking slope are less than λ/100.