Methods for laser processing rough transparent workpieces using pulsed laser beam focal lines and a fluid film

1. A method for processing a transparent workpiece, the method comprising:

applying a fluid film comprising a first refractive index of 1.01 to 1.09 to an impingement surface of the transparent workpiece, wherein the transparent workpiece comprises a second refractive index, wherein a difference between the first refractive index and the second refractive index is 0.8 or less, and wherein the impingement surface comprises a surface roughness Ra of 0.1 μm or greater; and

forming a defect in the transparent workpiece by directing a laser beam, oriented along a beam pathway and output by a beam source, through the fluid film, through the impingement surface, and into the transparent workpiece such that a portion of the laser beam directed into the transparent workpiece forms a laser beam focal line generating an induced absorption within the transparent workpiece, the induced absorption producing the defect within the transparent workpiece, wherein the portion of the laser beam directed into the transparent workpiece is a quasi-non-diffracting beam; and wherein the defect conforms to a shape of the quasi-non-diffracting beam and extends through the transparent workpiece.

2. The method of claim 1 , further comprising translating the transparent workpiece and the laser beam relative to each other along a contour line, thereby laser forming a contour comprising a plurality of defects within the transparent workpiece along the contour line.

3. The method of claim 2 , further comprising directing an infrared laser beam onto the transparent workpiece along the contour to separate the transparent workpiece along the contour.

4. The method of claim 1 , wherein the fluid film comprises water.

5. The method of claim 1 , wherein the fluid film comprises an index matching material, wherein the index matching material comprises a gel, an epoxy, or a polymer.

6. The method of claim 1 , wherein the difference between the first refractive index and the second refractive index is about 0.5 or less.

7. The method of claim 1 , wherein the first refractive index is equal to the second refractive index.

8. The method of claim 1 , wherein applying the fluid film to the impingement surface of the transparent workpiece comprises submerging the impingement surface in a fluid thereby forming the fluid film on the impingement surface of the transparent workpiece.

9. The method of claim 1 , wherein applying the fluid film to the impingement surface of the transparent workpiece comprises directing fluid from a fluid output mechanism onto the impingement surface.

10. The method of claim 1 , wherein the laser beam comprises a pulsed laser beam having a wavelength λ and wherein the transparent workpiece has combined losses due to linear absorption and scattering less than 20%/mm in a beam propagation direction.

11. The method of claim 1 , wherein a spacing between adjacent defects is 50 μm or less.

12. The method of claim 1 , wherein the pulsed laser beam propagates directly from free-space into the fluid film.

13. A method for processing a transparent workpiece, the method comprising:

applying a fluid film comprising a first refractive index to a impingement surface of the transparent workpiece, wherein the transparent workpiece comprises a second refractive index, a difference between the first refractive index and the second refractive index is about 0.8 or less, and the impingement surface comprises a surface roughness Ra of about 0.1 μm or greater;

forming a contour in the transparent workpiece along a contour line, the contour comprising a plurality of defects in the transparent workpiece, wherein forming the contour comprises:

directing a pulsed laser beam oriented along a beam pathway and output by a beam source, through an aspheric optical element, through the fluid film, through the impingement surface, and into the transparent workpiece such that a portion of the pulsed laser beam directed into the transparent workpiece generates an induced absorption within the transparent workpiece, the induced absorption producing a defect within the transparent workpiece and the portion of the pulsed laser beam directed into the transparent workpiece comprises:

a wavelength λ;

an effective spot size w o,eff ; and

a non-axisymmetric beam cross section that comprises a minimum Rayleigh range Z Rx,min in a cross-sectional x-direction and a minimum Rayleigh range Z Ry,min in a cross-sectional y-direction, wherein the smaller of Z Rx,min and Z Ry,min is greater than

F

D

⁢

π

⁢

⁢

w

0

,

eff

2

λ

,

where F D is a dimensionless divergence factor comprising a value of 10 or greater; and

translating the transparent workpiece and the pulsed laser beam relative to each other along the contour line, thereby laser forming the contour comprising the plurality of defects within the transparent workpiece along the contour line.

14. The method of claim 13 , further comprising directing an infrared laser beam onto the transparent workpiece along or near the contour to separate the transparent workpiece along the contour.

15. The method of claim 13 , wherein the fluid film comprises water.

16. The method of claim 13 , wherein the fluid film comprises an index matching material comprising a gel, an epoxy, or a polymer.

17. The method of claim 13 , wherein the first refractive index is equal to the second refractive index.

18. The method of claim 13 , wherein applying the fluid film to the impingement surface of the transparent workpiece comprises submerging the impingement surface in a fluid thereby forming the fluid film on the impingement surface of the transparent workpiece.

19. The method of claim 13 , wherein applying the fluid film to the impingement surface of the transparent workpiece comprises directing fluid from a fluid output mechanism onto the impingement surface.

20. The method of claim 1 , wherein a cross-section of the laser beam has an area that is uniform in the direction of propagation of the laser beam in the transparent workpiece.