Laser surface treatment

1. A process of developing a periodic structure in a surface of an optical transparent substrate, said process comprising the steps of:

forming a metal film having a thickness of 50 nm to 1000 nm on a surface of said optical transparent substrate made of non-metal material; and

irradiating an ultra-intense short-pulse laser beam having a pulse width of 1 femtosecond (fs) to 100 picoseconds (ps) to said metal film in order to ablate a portion of said metal film to generate within an ablated portion of said metal film, a resulting metal plasma, which interacts with said laser beam for etching the surface of said substrate, leaving a fine periodic structure having a periodic interval of 50 nm to 1000 nm in the surface thereof.

2. The process of developing a periodic structure in a surface of an optical transparent substrate as set forth in claim 1 , wherein said ultra-intense short-pulse laser beam is a circularly- or elliptically-polarized laser beam.

3. The process of developing a periodic structure in a surface of an optical transparent substrate as set forth in claim 1 , wherein said ultra-intense short-pulse laser beam is a linearly-polarized laser beam.

4. The process of developing a periodic structure in a surface of an optical transparent substrate as set forth in claim 1 , wherein said metal film is made of at least one selected from the group of copper, iron, gold, silver, aluminum, nickel, magnesium, titanium, silicon, stainless steels and alloys thereof.

5. The process of developing a periodic structure in a surface of an optical transparent substrate as set forth in claim 1 , wherein a laser energy density of said ultra-intense short-pulse laser beam is in a range of 1 to 100 mJ/mm 2 .

6. The process of developing a periodic structure in a surface of an optical transparent substrate as set forth in claim 1 , wherein said metal film is formed on a predetermined region of said substrate, and then all of said metal film on the predetermined region is removed by irradiation of said ultra-intense short-pulse laser beam, so that said fine periodic structure is formed on the predetermined region of said substrate exposed by the removal of said metal film.

7. The process of developing a periodic structure in a surface of an optical transparent substrate as set forth in claim 1 , further comprising the step of changing an irradiation angle of said ultra-intense short-pulse laser beam to said metal film to control said periodic interval of said fine periodic interval.

8. The process of developing a periodic structure in a surface of an optical transparent substrate as set forth in claim 1 , further comprising the step of performing an etching treatment to the surface of said substrate after the irradiation of said ultra-intense short-pulse laser beam.

9. The process of developing a periodic structure in a surface of an optical transparent substrate as set forth in claim 1 , further comprising the step of bonding the fine periodic structure of said substrate with a second substrate having a different refraction index from said substrate.

10. The process of developing a periodic structure in a surface of an optical transparent substrate as set forth in claim 9 , wherein the fine periodic structure of said substrate is bonded with said second substrate through an intermediate layer having a different refraction index from said substrate and said second substrate and a hardness smaller than said substrate and said second substrate.

11. The process of developing a periodic structure in a surface of an optical transparent substrate as set forth in claim 1 , wherein said non-metal material is selected from a group consisting of fused-silica, ZrF 4 -based glass, ThF 4 -based glass, BeF 2 -based glass, Ca F 2 -based glass, oxide glass, sapphire glass, ZnO-based glass, SiC-based glass, GaN-based glass, InN-based glass, YGA-based glass, GaAs-based glass, GaP-based glass, ZnS-based glass, ZnSe-based glass, SrS-based glass and CaGa 2 S 4 -based glass.