Device and method for coupling a laser beam into a double-clad fiber

A device for coupling a laser beam of a laser into a double-clad fiber, the device comprising:

• a first birefringent optical element configured to split the laser beam incident on a beam entry surface into two sub-laser beams, wherein the two sub-laser beams have first exit angles and/or first beam displacements with respect to a beam exit surface normal, wherein the two sub-laser beams are polarized along base polarization components of the first birefringent optical element,
• a polarization rotation device configured to adjust a polarization of the sub-laser beams to provide polarization-adjusted sub-laser beams,
• a second birefringent optical element, wherein a beam exit surface of the second birefringent optical element is first passed through by the polarization-adjusted sub-laser beams, and the first exit angles and/or the first beam displacements of the sub-laser beams from the first birefringent optical element are second angles of impingement and/or second beam displacements of the polarization-adjusted sub-laser beams relative to a beam exit surface normal of the second birefringent optical element,
• wherein the second birefringent optical element is configured to split each of the polarization-adjusted sub-laser beams into two sub-sub-laser beams, wherein the two sub-sub-laser beams have second exit angles and/or second beam displacements with respect to a beam entry surface normal of the second optical wedge, wherein the two sub-sub-laser beams are polarized along base polarization components of the second birefringent optical element, and
• wherein the second exit angles and/or the second beam displacements of the sub-sub-laser beams, a polarization of which corresponds to the polarization of the two sub-laser beams, compensate for the respective first exit angles and/or the first beam displacements, and
• an in-coupling optical unit configured to couple the sub-sub-laser beams with compensated first exit angles and/or first beam displacements into an inner core of the double-clad fiber, and to couple other sub-sub-laser beams into an annular core of the double-clad fiber.