The DPC is constituted by

The 1DPC is constituted by 20 alternating layers of Ta2O5 and SiO2, with (n = 2.1) and low (n = 1.45) refractive index respectively, deposited on a thin glass substrate by plasma ion assisted process under high vacuum conditions (APS904 coating system, Leybold Optics). The Ta2O5 and SiO2 layers are 95 and 137 nm thick respectively, while the top SiO2 layer is only 127 nm thick.