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1. (WO1998052258) IMPROVED LASER CUTTING METHODS
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WHAT IS CLAIMED IS:
1. A method of cutting a substrate comprising:
providing a laser that produces a stream of light pulses,
illuminating a surface of the substrate with the stream of light pulses, and
propagating a cutting surface created on the surface of the substrate by the stream of light pulses, with a heatwave and a Shockwave emanating from the cutting surface and vaporized substrate material present near the cutting surface, substantially all of the pulses having both a rise time to pulse length ratio sufficiently small enough and a fluence sufficiently large enough to enable the heatwave to travel sufficiently faster than the Shockwave to promote removal of the vaporized substrate material from the cutting surface.

2. The method of claim 1 , wherein the light pulse frequency ranges from about one hundred kilohertz to about five megahertz.

3. The method of claim 2, wherein the light pulse frequency ranges from about one megahertz to about five megahertz.

4. The method of claim 3, wherein the light pulse frequency ranges from about one megahertz to about 1.5 megahertz.

5. The method of claim 1, wherein the light pulses have a spatial distribution comprising top hat, Gaussian, or doughnut spatial distributions.

6. The method of claim 5, wherein the light pulses' spatial distribution is a top hat spatial distribution.

7. The method of claim 1, wherein the light pulses have a temporal distribution comprising square wave, and triangle wave temporal distributions.

8. The method of claim 7, wherein the light pulses' temporal distribution is a square wave temporal distribution.

9. The method of claim 1 , wherein the rise time of the light pulses is less than about five hundred picoseconds.

10. The method of claim 9, wherein the rise time of the light pulses is less than about three hundred picoseconds.

11. The method of claim 10, wherein the rise time of the light pulses is less than about one hundred picoseconds.

12. The method of claim 11 , wherein the rise time of the light pulses is less than about ten picoseconds.

13. The method of claim 1 , wherein the light pulses have a maximum fluence ranging from about one nanojoule to about one joule.

14. The method of claim 13, wherein the light pulses have a maximum fluence ranging from about one hundred nanojoules to about one hundred millijoules.

15. The method of claim 1 , wherein the light pulses have a duration ranging from about five picoseconds to about ten nanoseconds.

16. The method of claim 15, wherein the light pulses have a duration ranging from about fifty picoseconds to about five hundred nanoseconds.

17. The method of claim 1 , wherein the light pulses have an M-squared value less than about five.

18. The method of claim 17, wherein the light pulses have an M-squared value ranging from about one to about five.

19. The method of claim 18, wherein the light pulses have an M-squared value ranging from about 1.25 to about two.

20. The method of claim 1 , wherein the light pulses are polarized either
substantially randomly or substantially linearly.

21. The method of claim 20, wherein the light pulses are polarized substantially linearly.

22. The method of claim 1, wherein the light pulses have a wavelength ranging from about five hundred nanometers to about sixteen hundred nanometers.

23. The method of claim 22, wherein the light pulses have a wavelength ranging from about nine hundred and fifty nanometers to about eleven hundred nanometers.

24. The method of claim 23, wherein the light pulses have a wavelength of about one thousand seventy-nine point five nanometers.

25. The method of claim 1, wherein the light pulses are substantially multimode.

26. The method of claim 1 , wherein the light pulses are substantially only single mode.

27. The method of claim 1 , wherein a near solid density plasma is formed near the cutting surface.

28. The method of claim 1, wherein the substrate comprises semiconductors, dielectrics, polymers, metal, natural materials, and mixtures thereof.

29. The method of claim 28, wherein the semiconductors comprise silicon, gallium arsenide, or diamond.

30. The method of claim 29, wherein the substrate is a silicon wafer.

31. The method of claim 1 , further comprising:
positioning the substrate with respect to the stream of light pulses by moving the substrate.

32. The method of claim 1, further comprising:
positioning the stream of light pulses with respect to the substrate by redirecting the stream of light pulses.

33. A method for laser separation of a substrate comprising:
illuminating the substrate with a stream of light pulses having a pulse repetition frequency ranging from about five hundred kilohertz to about five megahertz, a rise time of less than about five hundred picoseconds, and a duration ranging from about fifty picoseconds to about five hundred nanoseconds.

34. The method of claim 33, wherein the pulses have a maximum fluence ranging from about one hundred nanojoules to about one hundred millijoules.

35. The method of claim 1 , wherein the stream of light pulses are substantially P-polarized.

36. The method of claim 1, wherein the stream of pulses has an average power of more than about ten watts.

37. The method of claim 36, wherein the stream of pulses has an average power of more than about twenty watts.

38. The method of claim 37, wherein the stream of pulses has an average power of more than about thirty watts.

39. The method of claim 38, wherein the stream of pulses has an average power of more than about forty watts.

40. A method of cutting a substrate comprising:
providing a laser that produces a stream of light pulses, wherein the frequency of pulses are about one megahertz; each pulse has a top hat spatial distribution; a square wave temporal distribution with a rise time of less than about ten picoseconds; a maximum fluence of about one millijoule; a duration of about six hundred and fifty picoseconds; the pulses having an M2 of about one point five; a substantially linear polarization state, a wavelength of about one thousand seventy nine point five nanometers; and being substantially single mode;
illuminating a surface of the substrate with the stream of light pulses,
propagating a cutting surface created on the surface of the substrate by the stream of light pulses, with a heatwave and a Shockwave emanating from the cutting surface and vaporized substrate material present near the cutting surface, and a near solid density plasma being formed near the cutting surface, and substantially all of the pulses having both a rise time to pulse length ratio sufficiently small enough and a fluence sufficiently large enough to enable the heatwave to travel sufficiently faster than the Shockwave to promote removal of the vaporized substrate material from the cutting surface.