Apparatus and method for laser interference structuring of substrates with periodic dot structures for anti-reflection properties

1 . A patterned substrate with anti-reflective properties, comprising a periodic dot structure in a micro- or sub-micrometer range;

wherein the periodic dot structure is formed of inverse cones;

wherein the inverse cones are arranged periodically with a distance from one another in a range of 50 nm to 50 μm;

wherein a quasi-periodic wave structure is superimposed on the periodic dot structure;

wherein the quasi-periodic wave structure has a sequence of wave crests and wave troughs with a periodicity in a range of 100 nm to 1000 nm; and

wherein the quasi-periodic wave structure is generated by utilizing laser-induced periodic surface structures (LIPSS).

2 . The patterned substrate according to claim 1 , wherein the periodic dot structure is formed such that the patterned substrate transmits electromagnetic radiation with a wavelength of more than 550 nm.

3 . The patterned substrate according to claim 1 , wherein the wave crests are arranged with a spacing in a range from 20 nm to 5 μm.

4 . The patterned substrate according to claim 1 , wherein the patterned substrate comprises a dot structure formed of a first interference pixel and a second interference pixel, the first interference pixel and the second interference pixel each independently comprise the periodic dot structure having dimensions in the micro- and/or sub-micrometer range, and the first interference pixel and the second interference pixel are arranged superimposed on each other such that an offset between the second interference pixel and the first interference pixel is in a range of 10%≤x≤50% of an interference period.

5 . The patterned substrate according to claim 1 , wherein the patterned substrate comprises a transparent material, and wherein the transparent material is selected from the group consisting of glass, solid polymers, and transparent ceramics.

6 . The patterned substrate according to claim 1 , wherein a refractive index of the patterned substrate is gradual.

7 . A laser interference patterning apparatus for direct laser interference patterning of a substrate for producing the patterned substrate according to claim 1 , comprising:

a laser radiation source ( 1 ) for emitting a laser beam,

a beam splitter element ( 2 ) arranged in an optical path ( 3 ) of the laser beam,

a focusing element ( 4 ) which is arranged in succession of the beam splitter element ( 2 ) in the optical path of the laser beam and configured so that sub-beams pass through it in such a way that the sub-beams are interfereable on a surface or in a volume of a substrate ( 5 ) in an interference region,

characterized in that,

the beam splitter ( 2 ) is freely movable along its optical axis in the optical path ( 3 ),

the beam splitter ( 2 ) is set up to split the laser beam emitted by the laser radiation source ( 1 ) into at least three sub-beams,

wherein a first deflecting element ( 7 ) is arranged in succession of the beam splitter element ( 2 ) in the optical path ( 3 ) of the laser radiation source ( 1 ), which is configured so that the at least three sub-beams are widened when passing through the first deflecting element ( 7 ).

8 . The apparatus according to claim 7 , wherein a further deflecting element ( 6 ) is arranged in succession to the laser radiation source ( 1 ) and the beam splitter element ( 2 ) in the optical path ( 3 ), which is configured so that it deflects the sub-beams in such a way that they run essentially parallel to one another after emerging from the further deflecting element ( 6 ).

9 . The apparatus according to claim 7 , wherein the deflecting element ( 7 ) is a concave lens.

10 . The apparatus according to claim 8 , wherein the further deflecting element ( 6 ) is a convex lens.

11 . The apparatus according to claim 7 , wherein the laser radiation source ( 1 ) is a pulsed laser radiation source with pulse widths in a range from 10 nanoseconds to 10 femtoseconds.

12 . A method for producing a substrate with a periodic dot structure in a micro- or sub-micrometer range by means of laser interference patterning, in particular for producing the patterned substrate according to claim 1 , comprising the following steps:

a) providing a substrate ( 5 ),

b) emitting a laser beam from a laser radiation source ( 1 ),

c) splitting the laser beam by means of a beam splitter element ( 2 ) into at least three sub-beams,

d) focusing the sub-beams onto a surface or within a volume of the substrate ( 5 ), so that the sub-beams interfere constructively and destructively on the surface or within the volume of the substrate ( 5 ),

characterized in that the at least three sub-beams are superimposed on the substrate ( 5 ) by the focusing such that the periodic dot structure in the micro- or sub-micrometer range is generated on the surface or in the volume of the substrate ( 5 ),

wherein the periodic dot structure is formed of the inverse cones,

wherein the inverse cones are arranged periodically at the distance from one another in the range from 50 nm to 50 μm,

wherein the quasi-periodic wave structure is superimposed on the periodic dot structure,

wherein the quasi-periodic wave structure has the sequence of wave crests and wave troughs with the periodicity in the range of 100 nm to 1000 nm.

13 . The method according to claim 12 , wherein a structure period of the generated periodic dot structure of the substrate ( 5 ) is steplessly adjustable in the micro- or sub-micrometer range by moving the beam splitter element ( 2 ) along its optical axis in an optical path ( 3 ) of laser beam.

14 . The method according to claim 12 , wherein the substrate ( 5 ) comprises a transparent material and the sub-beams interfere inside the transparent material.

15 . The method according to claim 12 , comprising the following steps:

applying a first pulse on the surface of the substrate ( 5 ), which generates a first interference pixel on the surface of the substrate ( 5 ) or within the volume of the substrate ( 5 ),

applying a second pulse to the surface of the substrate ( 5 ), which generates a second interference pixel on the surface of the substrate ( 5 ) or within the volume of the substrate ( 5 ),

wherein the first and second interference pixels each independently comprise the periodic dot structure with dimensions in the micro- and sub-micrometer range,

characterized in that an offset between the second interference pixel and the first interference pixel is in a range of 10%≤x≤50% of an interference period.

16 . The method according to claim 15 , wherein after step b), a third pulse is applied on the surface of the substrate ( 5 ),

wherein the third pulse generates a third interference pixel on the surface of the substrate ( 5 ) or within the volume of the substrate ( 5 ), wherein the third interference pixel has an offset in the range of 10%≤x≤50% of the interference period with respect to the second interference pixel, and wherein the third interference pixel comprises a periodic dot structure with dimensions in the micro- and sub-micrometer range.

17 . The method according to claim 15 , wherein the offset of the interference period is uniform in at least one spatial direction.

18 . A process comprising:

utilizing the patterned substrate according to claim 1 in photovoltaic systems.

19 . A process comprising:

utilizing the patterned substrate according to claim 1 as anti-reflective glazing of monitors, screens and displays.

20 . A process comprising:

utilizing the patterned substrate according to claim 1 in glass fibers.

21 . A process comprising:

utilizing the patterned substrate according to claim 1 as a negative mold for indirectly applying or creating patterns on another substrate.