METHOD FOR PRODUCING AN OPTICAL COMPONENT BY MEANS OF LASER RADIATION

Abstract

The invention relates to a method for producing an optical component (1) by means of laser radiation. The object of the invention is that of providing a method that is improved compared with the prior art, which method allows for the correction of deviations of the optical functionality of the component from specified target parameters. For this purpose, the method according to the invention comprises the following method steps: generating a structure in the material of the component (1) which gives the component (1) an optical functionality, and modifying the refractive index in the material of the component (1) by means of laser beams in a pre- and/or post-processing step, i.e. before or after the generation of the structure, in order to correct deviations of the optical functionality of the component (1) from specified target parameters.

Claims

1. Method for producing an optical component (1) by means of laser radiation, comprising the following method steps: generating a structure in the material of the component (1) which gives the component (1) an optical functionality, and modifying the refractive index in the material of the component (1) by means of laser beams in a pre- and/or post-processing step, i.e. before or after the generation of the structure, in order to correct deviations of the optical functionality of the component (1) from specified target parameters.

2. Method according to claim 1, characterized in that the laser radiation used for modifying the refractive index in the pre- and/or post-processing step is pulsed, wherein the pulse duration is from 10 fs to 10 ps, and the central wavelength is in the range of from 150 nm to 10 μm.

3. Method according to claim 1, characterized in that, in the pre- and/or post-processing step, beam shaping and/or beam deflection of the laser radiation directed onto the component (1) takes place, in order to generate a spatially variable modification of the refractive index in the material of the component (1).

4. Method according to claim 3, characterized in that the beam shaping and/or beam deflection is achieved by means of focusing optics (3) and/or adaptive optics (4).

5. Method according to claim 3, characterized in that the spatially variable modification of the refractive index is superimposed on the structure that determines the optical functionality in the material of the component (1).

6. Method according to claim 3, characterized in that, in order to generate the spatially variable modification, the pulse energy, the repetition rate and/or the number of laser pulses applied in the material of the component (1), per volume or per surface area, is varied.

7. Method according to claim 1, characterized in that the component (1) is clamped in a retainer during the modification of the refractive index, and/or an immersion fluid is used for coupling the laser radiation into the material of the component (1).

8. Method according to claim 1, characterized in that the optical component (1) is an optical fiber or an optical fiber system, in particular a single core or multicore optical fiber.

9. Method according to claim 1, characterized in that the optical functionality is that of an optical grating, in particular a fiber Bragg grating, an aperiodic fiber Bragg grating, a long-period grating, or a volume Bragg grating.

10. Method according to claim 1, characterized in that the target parameters determine a central operating wavelength and/or a dispersion of the component (1).

Description

[0021] The graphs of FIG. 1 show different refractive index profiles n(x) along the longitudinal axis x of an optical fiber. The solid curve in each case specifies the refractive index profile n(x), which was first generated as a structure in the material of the component 1, in order to provide the component with its optional functionality, in this case a periodic structure (Bragg grating) as a narrow-band reflector. The arrow in each of the graphs indicates how the refractive index is modified in a post-processing step, such that the refractive index profile n(x) according to the dashed curve, in each case, results. In this case, the local change in the refractive index does not necessarily always have to be positive.

[0022] FIG. 2 schematically shows an arrangement, by means of which, according to the invention, a refractive index modification can be introduced into the material of the component, in a pre- or post-processing step.

[0023] An ultrashort pulse laser 2 having a central wavelength from the range of 150 nm to 10 μm, having possible pulse lengths in the range of from 10 fs to 10 ps, is used as the laser source. All types of transparent, partially transparent, or absorptive materials (for the laser central wavelength used in each case) are suitable as materials of the component 1 to be processed, which materials may be provided for example as an optical fiber with and without a coating, as a bulk material with and without waveguides, etc. In order to overcome a possible surface curvature or another curvature of the component (e.g. curvature of the fiber surface), said component can also be located in a corresponding retainer (not shown), optionally supplemented by an immersion fluid for coupling in the laser radiation used for refractive index modification.

[0024] The use of the ultrashort laser pulses allows for the local modification of the material. A strongly localized change in the refractive index is thus possible. Furthermore, the ultrashort pulses of the laser radiation allow for the modification of transparent (or partially transparent) materials. The region in the material of the component to be processed is expediently addressed by means of beam shaping or scanning of the laser beam. The magnitude of the refractive index change can be controlled inter alia by the pulse energy, the number of pulses per surface area or per volume, and the repetition rate of the laser.

[0025] The centrally reflected wavelength of a Bragg grating can be changed by means of a uniform change of the refractive index, as shown in FIG. 1a.

[0026] A modification of the refractive index that increases (or drops) to one side of the component, as shown in FIG. 1b, can be used to change the dispersive and reflective properties.

[0027] Furthermore, nonlinear progressions of the refractive index modification are conceivable, in order to obtain desired complex dispersion and reflection profiles. An example of how a nonlinear progression of this kind, impressed on a periodic structure, can appear, is shown in FIG. 1c.

[0028] In order to carry out the pre- or post-processing according to the invention, various optical assemblies can be used. It is possible for example, as indicated in FIG. 2, for imaging focusing optics 3 (comprising spherical or cylindrical lenses, freeform optics, curved mirrors, etc.), if necessary also in combination with flexible adaptive optics 4, to be used for beam shaping, for the purpose of targeted local modification. As a result, both extensive and also local pre- and/or post-processing is possible. In the event of post-processing of structures inside or in the effective region of an optical fiber (e.g. inside a coated fiber), the laser radiation can also be coupled into these.