Research on high surface shape accuracy filter fabricated by dual-deposition method

The preparation of high surface shape accuracy bandpass filter by double-sided coating method was studied, and the HWB900 substrate high surface shape accuracy bandpass filter film with outer diameter of Φ 25 mm and diameter-thickness ratio of 10:1 was prepared by dual-deposition. On one side the bandpass filter film was deposited and the matching layer was then coated to eliminate the stress-induced deformation on the other side. The results show that the mean transmittance \bar\tau is greater than or equal to 92% in the passband between 1 215 nm~1 265 nm, the transmittance \bar\tau_max is less than 1% in the rejection band between 900 nm~1 135 nm and 1 345 nm~1 700 nm, and the root-mean-square (RMS) values of both side are superior than λ/20. Following a comprehensive analysis of the deformation law in both side, the thickness of the matching layer and the use characteristics of this method were determined. The described method has high practicality, and the prepared optical devices have excellent optical performance and high surface accuracy, which has important reference value and guiding significance for the preparation of optical devices with high surface shape accuracy.