Patent Number: 
Section: claims

1. An optical element, comprising:a substrate, anda multilayer coating applied to the substrate and configured to reflect extreme ultraviolet (EUV) radiation, and having a surface,wherein a surface structure at the surface of the multilayer coating reduces adhesion of contaminating particles, wherein the surface structure has pore-shaped depressions separated from one another by webs, and wherein the pore-shaped depressions have respective diameters (dV) which are smaller than diameters (dP) of the contaminating particles. 2. The optical element according to claim 1, wherein the pore-shaped depressions have a diameter (dv) of less than 10 nm. 3. The optical element according to claim 1, wherein web widths (B) of the surface structure are smaller than the respective diameters (dv) of the pore-shaped depressions of the surface structure. 4. The optical element according to claim 1, wherein a depth (T) of a respective pore-shaped depression is at least as large as half the diameter (dV/2) of a respective one of the pore-shaped depressions. 5. The optical element according to claim 1, wherein the surface structure has at least one periodic pore structure. 6. The optical element according to claim 5, wherein the at least one periodic pore structure has a period length (dS, dS3) of less than 10 nm. 7. The optical element according to claim 5, wherein the surface structure has a first periodic pore structure having a first period length (dS1) and a second periodic pore structure applied to the first periodic pore structure and having a second period length (dS2) which is smaller than the period length (dS1) of the first periodic pore structure. 8. The optical element according to claim 7, wherein the first period length (dS1) is at least five times the second period length (dS2).