Design of high reflection coating in ＣＯＩＬ resonator at 45° incidence

From the electric field distribution and the phase shift requirement for the film, the mirror coating in COIL resonator at 45 deg incidence angle is designed using multiple frequency design method. A new high reflection design at two wavelengths (632.8nm and 1315nm) is attained with 180 deg phase retard at 1315nm. Compared with the conventional design, the thickness of high refractive index material of the new design is reduced largely. Hopefully, the performance of the mirror can be improved greatly.