Method for laser machining transparent materials

• US 8,350,183 B2
• Filed: 06/07/2008
• Issued: 01/08/2013
• Est. Priority Date: 06/14/2007
• Status: Active Grant

• Current Assignee: Gerrsheimer Regensburg GmbH
• Original Assignee: Universitat Zu Lubeck
• Inventors: Vogel, Alfred, Linz, Norbert, Freidank, Sebastian
• Primary Examiner(s): HO, HOANG QUAN TRAN
• Application Number:
  US12/663,728
• Publication Number:
  US 20100163540A1
• Time in Patent Office: 1,676 Days
• Field of Search: None
• US Class Current: 219/121.62
• CPC Class Codes: A61F 9/008 using laser
• CPC Class Codes: A61F 9/00825 for photodisruption
• 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 26/03 Observing, e.g. monitoring, the workpiece
• CPC Class Codes: B23K 26/0624 using ultrashort pulses, i.e. pulses of 1ns or less
• CPC Class Codes: B23K 26/40 taking account of the properties of the material involved
• CPC Class Codes: B23K 26/55 for creating voids inside the workpiece, e.g. for forming flow passages or flow patterns

Abstract

A method for machining a transparent material by the non-linear absorption of pulsed laser radiation, in the region of a laser focus, includes the following steps: a laser wavelength of between 300 and 1000 μm is selected; and laser impulses having a temporally flat beam profile are applied. The method is characterized in that the irradiation intensity is selected from an interval pre-determined for the material to be machined, in which plasma is formed without plasma luminescence. An apparatus for laser treating a transparent material includes structure to set an irradiance and inspect the treatment as being within a defined interval.

Claims

1. Method for treating a transparent material by non-linear absorption of pulsed laser radiation taking place in the area of a laser focus, having the following steps

Selecting a laser wavelength from an interval from 300 ps to 1000 nm,

Selecting a pulse length from an interval from 300 ps to 20 ns,

Applying laser pulses with a temporal smooth beam profile, characterised in that

an irradiance is selected from an interval predetermined for the material to be treated, in which plasma formation occurs without plasma luminescence.

2. Method according to claim 1, characterised in that the interval predetermined for the irradiance is determined as a function of the material to be treated by varying the irradiance in the laser focus by inspection of the treatment success, a lower interval limit of the irradiance being determined using a detection limit of the inspection and an upper interval limit using the occurrence of plasma luminescence.

3. Method according to claim 1, characterised in that the transparent material is a liquid medium and bubbles with a fixedly selected radius are formed in the liquid medium.

4. Method according to claim 3, characterised in that the transparent material is an aqueous medium and the irradiance for the aqueous medium is at least 90 GW/cm².

5. Method according of claim 1, characterised in that the transparent material is a solid and cavities are formed in the solid.

6. Method according to one of claim 1, characterised in that the transparent material is a solid and a refractive index in the solid is changed locally.

7. Method according to claim 1, characterised in that a pulse duration is at least three times a time constant of a plasma recombination of the material to be treated.

8. Method according to claim 1, characterised in that a pulse duration is selected from an interval from 0.9 to 11 ns.

9. Apparatus comprising:

a laser for treating a transparent material by non-linear absorption of pulsed laser radiation taking place in an area of a laser focus, having a wavelength in a range from 300 to 1000 nm and a pulse length in a range from 300 ps to 20 ns,

means for setting an irradiance, the laser producing laser pulses with a temporally smooth beam profile, and

inspection means that register a treatment success of the laser and act on the means for setting the irradiance in such a way that the irradiance is within an interval between a detection limit of the inspection and an occurrence of plasma luminescence in the material treated.

10. Apparatus according to claim 9, characterised in that the inspection means register bubble formation taking place during the treatment in the material treated.

11. Apparatus according to claim 9, characterised in that the laser is a seeded solid-state laser or a microchip laser.