Optical waveguides – With optical coupler – Input/output coupler
Patent
1998-01-23
2000-04-25
Palmer, Phan T. H.
Optical waveguides
With optical coupler
Input/output coupler
385 17, 385 15, 385 24, 385 27, 359623, 359619, G02B 632
Patent
active
060553464
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention concerns a fibre optic device for homogenizing a laser beam.
It finds a general application in any technical field using a laser, and notably in laser surface treatment, such as the annealing of amorphous silicon, cleaning, polishing and surface preparation.
In general terms, the energy distribution across the cross section of a laser beam, at least in the lowest type of emission, has a gaussian appearance, which is in any case variable across the cross section of the beam.
However, in order to obtain, for example, an optimum annealing of amorphous silicon, it is necessary to apply a laser beam having a homogeneous and substantially uniform energy distribution.
This homogeneity is particularly required when the sample to be treated by laser is of large size (as described in the French Patent Application entitled "Device and method for laser surface treatment" filed in the name of the Applicant on Aug. 11, 1995 under the number 95 09778, and the disclosure of which is incorporated herein by reference. It is also required when the incident laser beam is a combination of several laser beams coming from a line of laser units arranged in parallel and/or in series (as described in the French Patent Application entitled "Method and device for controlling a laser source with several laser units for optimizing laser surface treatment", filed by the Applicant on Aug. 11, 1995 under the number 95 09780, and the disclosure of which is incorporated herein by reference.
Means are already known for homogenizing a laser beam (JP-A-01 286 478, U.S. Pat. No. 5,253,110, EP-A-0 266 120, DE-A-4 220 705 and EP-A-0 097 250).
However, these means are usually complicated, expensive, difficult to implement and ill-suited to beams of large size and high power.
The present invention affords precisely a solution to this problem.
SUMMARY OF THE INVENTION
It relates to an optical-fibre device for treating an entrance laser beam comprising: and n columns, on a plane perpendicular to the direction of propagation of the entrance laser beam and suitable for dividing the said entrance laser beam into m.times.n elementary laser beams each having an elementary transverse section of chosen geometric shape and a spatial distribution of the light intensity which is substantially homogenous in the elementary section, and direction of propagation of the entrance laser beam, downstream of the front lenses in the direction of travel of the entrance laser beam, the said collection lens then being suitable focusing, in a chosen plane, the elementary beams coming from the front lenses, with a view to obtaining an exit beam having a desired spatial distribution of the energy density.
According to a general definition of the invention, the device also comprises: opposite the first, the first optical fibre ends being disposed in a first matrix arrangement of i rows and j columns in a first intermediate plane, formed by the focal plane of the front lenses, with each of the first optical fibre ends substantially situated at the focal point of a respective front lens, whilst the second optical fibre ends being disposed in a second bidimensional arrangement of chosen distribution in a second intermediate plane situated downstream of the said focal plane of the front lenses, the first and second optical fibre ends constituting respectively entrance pupils and exit pupils and the collection lens, disposed downstream of the second intermediate plane, being able to collect the elementary beams coming from the plurality of exit pupils.
The optical fibres are thus able to transfer a plurality of homogeneous elementary portions of the laser energy. In the case of a high-power laser, the device according to the invention thus makes it possible to divide and transfer a laser energy into a plurality of homogeneous elementary portions of low-power energy. There is a resulting elimination of the damage which may be caused by the effects of a high-power laser, notably on the optical elements of the device according to t
REFERENCES:
patent: 5253110 (1993-10-01), Ichihara et al.
patent: 5414559 (1995-05-01), Burghardt et al.
Godard Bruno
Stehle Robert
Palmer Phan T. H.
Societe de Production et de Recherches Appliquees
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