Fabrication and measurement of low polarization anti-reflection coating at 248 nm

Coating induced polarization state variation cannot be neglected, if the angle of incidence (AOI) is too large. LaF3 and MgF2 are chosen as high and low index material to design the low polarization anti-reflection (LPAR) coating. After proper fabrication and measurement, the transmittance of the LPAR coating is 98.6%, and the differential transmittance between P and S polarized direction of the LPAR one is about 3%, which is much smaller than 15% caused by the common anti-reflection (AR) coating. Moreover, with and without the LPAR coating, the Peak and Valley (PV) values of the substrate were 1.572λ and 1.457λ (λ = 632.8 nm), which meant the mechanical stress of the coating was well controlled.