METHOD AND DEVICE FOR SHIELDING A HIGH POWER LASER APPARATUS AND HIGH-POWER-LASER OPTICAL SYSTEM EMPLOYING SUCH A DEVICE

• US 20100296534A1
• Filed: 10/13/2008
• Published: 11/25/2010
• Est. Priority Date: 10/15/2007
• Status: Active Grant

• Current Assignee: Amplitude Technologies SA, Imagine Optic
• Original Assignee: Amplitude Technologies SA, Imagine Optic
• Inventors: Riboulet, Gilles, Levecq, Xavier
• Granted Patent: US 8,971,363 B2
• Time in Patent Office: Days
• US Class Current: 372/29.023
• CPC Class Codes: G02B 26/06 for controlling the phase of light G02B26/08 takes precedence , measuring optical phase difference G01J9/00
• CPC Class Codes: G02B 27/46 Systems using spatial filters
• CPC Class Codes: H01S 3/0014 Monitoring arrangements not otherwise provided for photometry G01J1/00, e.g. G01J1/4257; radiation pyrometry G01J5/00; measuring coherence of light G01J9/00; measuring wavelength of light G01J9/00, e.g. G01J9/0246; measuring optical pulses G01J11/00; calorimetrically measuring power of laser beams G01K17/003
• CPC Class Codes: H01S 3/005 Optical devices external to the laser cavity, specially adapted for lasers, e.g. for homogenisation of the beam or for manipulating laser pulses, e.g. pulse shaping shaping laser beam for working metal or other materials B23K26/06; optical elements, systems or apparatus in general G02B
• CPC Class Codes: H01S 3/0078 Frequency filtering
• CPC Class Codes: H01S 3/2316 Cascaded amplifiers

Abstract

Method for shielding a high-power laser apparatus (S) in which a laser beam is generated and then amplified in at least a first amplification stage, including spatial filtering (4) of the amplified laser beam, phase correction (3) carried out on the laser beam before it is spatially filtered, and a measurement of the aberrations (7) on the laser beam. The phase of the beam is corrected so as to produce a beam having minimal aberrations after spatial filtering. The shielding device (D, D′) implementing this method may in particular be employed in apparatus using an intense laser beam of high (terawatt) peak power and in proton therapy units.

Claims

1. Method for shielding a high-power laser apparatus (S) in which a laser beam is generated and then amplified in at least a first amplification stage, comprising spatial filtering (4) of said amplified laser beam, phase correction (3) carried out on the laser beam prior to its spatial filtering, and measurement of aberrations (7) carried out on the laser beam, characterized in that the phase correction of the beam is controlled so as to produce a beam with minimized aberrations after spatial filtering.

2. Method of shielding according to claim 1, characterized in that the measurement of aberrations (7) is carried out before the spatial filtering (4) of the laser beam.

3. Method of shielding according to claim 1, characterized in that the measurement of aberrations (7) is carried out after the spatial filtering (4) of the laser beam.

4. Method of shielding according to claim 3, characterized in that it additionally comprises a translation (9) of spatial filtering means (4) in a direction approximately orthogonal to the direction of the spatially filtered beam, so that said spatial filtering means (4) are withdrawn from said beam to permit measurement of the aberrations (7) of the wave front.

5. Method of shielding according to claim 1, characterized in that it additionally comprises a sampling (8) of a fraction of the corrected laser beam, which is then subjected to a measurement of aberrations (7).

6. Method of shielding according to claim 1, characterized in that the spatial filtering (4) of the laser beam is provided by a filter pinhole the size of which is selected so as to eliminate, from said beam, the aberrations at spatial frequencies that can give rise, by propagation, to surges in said beam.

7. Method of shielding according to claim 6, characterized in that the size of the filter pinhole (4) is selected to be approximately 10 times less than the diffraction limit of the laser beam.

8. Method of shielding according to claim 6, characterized in that it additionally comprises detection of degradation of the filter pinhole.

26. Application of the method of shielding according to claim 1, in a proton therapy apparatus.

27. Application of the method of shielding according to claim 1, in an installation for experimentation at high peak power.

9. Device (D, D′

) for shielding a high-power laser apparatus (S) comprising means (1) for generating a laser beam and first means (2) for amplifying this laser beam, this device comprising spatial filtering means (4) receiving said amplified laser beam, means (3) for correcting the phase of the beam arranged upstream of said spatial filtering means (4), and means (7) for measuring aberration arranged downstream of said phase correction means (3), characterized in that the means (3) for correcting the phase of the beam are controlled so as to produce a beam with minimized aberrations after spatial filtering.

10. Shielding device (D, D′

) according to claim 9, characterized in that it additionally comprises means (10) for detecting degradation of the spatial filtering means.

11. Shielding device according to claim 10, characterized in that the means for detecting degradation (10) comprise a camera for imaging the spatial filtering means.

12. Shielding device (D) according to claim 9, characterized in that the means for measuring aberration (7) are arranged upstream of the spatial filtering means (4).

13. Shielding device (D′

) according to claim 9, characterized in that the means for measuring aberration (7) are arranged downstream of the spatial filtering means (4).

14. Shielding device (D′

) according to claim 13, characterized in that it additionally comprises means (9) for effecting translation of the spatial filtering means (4) in a direction approximately orthogonal to the direction of the beam coming from said spatial filtering means (4).

15. Shielding device (D, D′

) according to claim 9, characterized in that it additionally comprises means (8) for sampling a fraction of the laser beam downstream of said phase correction means (2) and directing said fraction towards the means for measuring aberration (7).

16. Shielding device (D, D′

) according to claim 9, characterized in that the phase correction means (3) comprise a deformable mirror (30).

17. Shielding device according to claim 9, characterized in that the phase correction means are arranged at the entrance of the amplification means and the spatial filtering means and the means for measuring aberration are arranged at the exit of said amplification means.

18. High-power-laser optical system (S), comprising means (1) for generating a laser beam, means (2) for amplifying said laser beam, means (4) for spatially filtering said laser beam, means (5) for focusing said spatially filtered beam onto a target (6), phase correction means (3) upstream of said spatial filtering means (4), and means (7) for measuring the aberration of the beam arranged downstream of said phase correction means (3), characterized in that the means for correcting the phase of the beam are controlled so as to produce a beam with minimized aberrations after spatial filtering.

19. System (S) according to claim 18, characterized in that it additionally comprises means for amplifying the laser beam coming from the spatial filtering means.

20. System (S) according to claim 18, characterized in that it additionally comprises means for compressing the laser beam coming from the spatial filtering means.

21. System (S) according to claim 18, characterized in that it additionally comprises means (10) for detecting degradation of the spatial filtering means.

22. System (S) according to claim 18, characterized in that the means for measuring aberration (7) are arranged upstream of the spatial filtering means (4).

23. System (S) according to claim 18, characterized in that the means for measuring aberration (7) are arranged downstream of the spatial filtering means (4).

24. System (S) according to claim 23, characterized in that it additionally comprises means (9) for effecting translation of the spatial filtering means (4) in a direction approximately orthogonal to the direction of the beam passing through said spatial filtering means (4).

25. System (S) according to claim 18, characterized in that it additionally comprises means (8) for sampling a fraction of the laser beam downstream of said phase correction means (3), and for directing this sampled fraction towards the means for measuring aberration (7).