Burst-ultrafast laser machining method

• US 6,552,301 B2
• Filed: 01/25/2001
• Issued: 04/22/2003
• Est. Priority Date: 01/25/2000
• Status: Active Grant

• Current Assignee: Anton Oettl, Peter R. Herman, Robin Marjoribanks
• Original Assignee: Anton Oettl, Peter R. Herman, Robin Marjoribanks
• Inventors: Herman, Peter R., Oettl, Anton, Marjoribanks, Robin
• Primary Examiner(s): Dunn, Tom
• Assistant Examiner(s): EDMONDSON, LYNNE RENEE
• Application Number:
  US09/768,785
• Publication Number:
  US 20010009250A1
• Time in Patent Office: 817 Days
• Field of Search: 219/121.71, 219/121.7, 219/121-7-1, 372/25, 372/53, 606/10
• US Class Current: 219/121.71
• CPC Class Codes: A61B 2017/00172 Pulse trains, bursts, intermittent continuous operation
• CPC Class Codes: A61F 2009/00842 Permanent Structural Change [PSC] in index of refraction; Limit between ablation and plasma ignition
• CPC Class Codes: A61F 2009/00872 Cornea
• CPC Class Codes: A61F 9/00802 for photoablation
• CPC Class Codes: A61F 9/00817 Beam shaping with masks
• CPC Class Codes: B23K 2103/10 Aluminium or alloys thereof
• CPC Class Codes: B23K 2103/172 wherein at least one of the layers is non-metallic
• CPC Class Codes: B23K 2103/32 Material from living organisms, e.g. skins
• CPC Class Codes: B23K 2103/50 Inorganic material, e.g. metals, not provided for in B23K2103/02 – B23K2103/26
• CPC Class Codes: B23K 2103/52 Ceramics
• CPC Class Codes: B23K 26/0624 using ultrashort pulses, i.e. pulses of 1ns or less
• CPC Class Codes: B23K 26/361 for deburring or mechanical trimming B23K26/351 takes precedence
• CPC Class Codes: B23K 26/364 for making a groove or trench, e.g. for scribing a break initiation groove
• CPC Class Codes: B23K 26/389 of fluid openings, e.g. nozzles, jets laser machining of inkjet nozzles B41J2/1634
• CPC Class Codes: B23K 26/40 taking account of the properties of the material involved
• CPC Class Codes: B23K 26/60 Preliminary treatment
• CPC Class Codes: C03B 29/02 in a discontinuous way
• CPC Class Codes: C03B 33/082 using a focussed radiation beam, e.g. laser C03B33/0855 takes precedence
• CPC Class Codes: C03C 23/0025 by a laser beam

Abstract

A method of laser processing or laser modification of materials. The combination of ultrafast laser pulses and high-repetition rate (>100 kHz) bursts (or continuous operation) defines a new and unexpected regime for material processing. The high repetition rate controls thermal and/or other relaxation processes evolving between each ultrafast laser pulse that ‘prepares’ the sample surface or bulk to alter the interaction with subsequent ultrafast laser pulses and thereby improve or optimize the process, or enable a new process, that are not available at lower repetition rate. The addition of this laser-controlled thermal component, and/or the general control of relaxation processes, overcomes several current limitations of ultrafast laser processing at lower repetition rates (<100 kHz), providing means to further harness the many attributes of ultrafast lasers for general material processing and material modification applications.

Claims

1. A method of laser induced modification of a material, comprising:

applying at least one burst of laser pulses to a material, the laser pulses having a time separation between individual laser pulses in a range appropriate so as to exploit the persistence of a selected transient effect arising from the interaction of a previous pulse with the material, said laser pulses having a pulse width of less than about 10 picoseconds, and collectively having fluence above a threshold value for modification of said material.

2. The method according to claim 1, wherein the time separation between individual laser pulses is less than a maximum time determined by a characteristic relaxation time of said transient effect.

3. The method according to claim 2, wherein said transient effect is thermal transport and said maximum time separation between individual pulses is about 10 microseconds, this value being determined by material characteristics and interaction geometry between said laser pulses and said material.

4. The method according to claim 3 wherein said at least one burst of laser pulses includes a preselected number of laser pulses greater than or equal to two.

5. The method according to claim 3 including detecting electromagnetic radiation emitted from a portion of said material at which said laser pulses are applied for spectroscopic analysis.

6. The method according to claim 3 including coating a substrate placed in close proximity to said material, wherein said substrate is coated by spallation or evaporation of matter ejected from said material.

7. The method according to claim 3 wherein said material is glass and said modification is drilling holes therein, cutting or machining a surface of said glass, and wherein said pulse widths are less than about 10 picoseconds and pulse-separation times are less than 10 about microseconds.

8. The method according to claim 3 wherein said material is a dielectric and said modification is drilling holes therein, cutting or machining a surface of said dielectrics, and wherein said pulse widths are less than about 10 picoseconds and pulse-separation times are less than 10 about microseconds.

9. The method according to claim 3 wherein said material is a semiconductor and said modification is drilling holes therein, cutting or machining a surface of said semiconductor, and wherein said pulse widths are less than about 10 picoseconds and pulse-separation times are less than 10 about microseconds.

10. The method according to claim 3 wherein said material is metal and said modification is drilling holes therein, cutting or machining a surface of said metal, and wherein said pulse widths are less than about 10 picoseconds and pulse-separation times are less than about 10 microseconds.

11. The method according to claim 10 wherein said metal is aluminum.

12. The method according to claim 3 wherein said material is a ceramic and said modification is drilling holes therein, cutting or machining a surface of said ceramic, and wherein said pulse widths are less than about 10 picoseconds and pulse-separation times are less than about 10 microseconds.

13. The method according to claim 3 wherein said material is glass and said modification is altering an index of refraction at a surface or within a bulk of the glass, and wherein said pulse widths are less than about 1 picosecond and pulse-separation times are less than about 10 microseconds.

14. The method according to claim 3 wherein said material is glass and said modification is mechanical modification including compactification, inducing stress/strain features, relief of stress/strain features, or optical damage.

15. The method according to claim 3 wherein said material is substantially transparent biological tissue and said modification is photorefractive surgery, or diffractive correction, by tissue ablation.

16. The method according to claim 3 wherein said material is substantially transparent biological tissue and said modification is photorefractive surgery, or diffractive correction, by tissue modification, including protein denaturation.

17. The method according to claim 3 wherein said material is protein and wherein said modification is protein denaturation.

18. The method according to claim 3 wherein an amplitude of the pulsetrain is shaped or controlled so that individual pulses have intensities different from other pulses in the pulsetrain and tailored to a specific material or processing application.

19. The method according to claim 18 wherein a spatial intensity of the laser pulsetrain burst is determined by optical imagining, including patterning by optical amplitude-masks or by diffractive optical elements.