Objective GREGOR is an assembled solar telescope with 1. 5 m diameter that is designed for highprecision measurements of the magnetic field and gas motion in the solar photosphere and chromosphere with a resolution of 70 km on the sun and highresolution stellar spectroscopy. To meet the specific requirements of measurement using the GREGOR telescope system , the surfaces of the lenses need to be modified using interference coatings. These coatings form the optical filters required to achieve the rejection bands at the specific wavelength ranges originating from fluorescence. Therefore, a multinotch filter covering visible light with high transmittance for passbands and high optical density for rejection bands is designed and fabricated to improve the signaltonoise ratio, where the noise signals are rejected.Methods In this design, two materials with high and low refractive indices are employed and the ripples in the passband regions are 研究论文 第 50 卷 第 13 期/2023 年 7 月/中国激光 coatings are produced by ionbeamassisted reactive magnetron sputtering deposition technology with a high deposition rate and low stress.Conclusions The apodization thickness modulated design method presented in this work generates notch filter designs with strongly suppressed ripples in the transmission regions and high optical density for the rejection bands. The total layer number of the multinotch filter is 190 and the total filter thickness is approximately 20 μm. The good performance multinotch filter is deposited successfully. The multinotch filter is prepared by ionbeamassisted reactive magnetron sputtering on B270. Optical monitoring and time control methods are utilized to monitor the nonquarter thickness. The average transmittance in the passbands of the fabricated multinotch filter is higher than 90%, the cutoff depth for the rejection bands is better than 0.1%, the full width at half maximum of the rejection bands is less than 24 nm, and the maximum deviation of the band position is 2 nm. This indicates the fabricated multinotch filter with excellent performance and high production yield meets the specified requirements for the GREGOR telescope application.
