Optical: systems and elements – Single channel simultaneously to or from plural channels – By refraction at beam splitting or combining surface
Reexamination Certificate
2001-08-24
2004-01-27
Epps, Georgia (Department: 2873)
Optical: systems and elements
Single channel simultaneously to or from plural channels
By refraction at beam splitting or combining surface
C359S623000, C359S626000
Reexamination Certificate
active
06683727
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
The present application is a National Stage Application of International Application No. PCT/EP00/02708, filed Mar. 28, 2000. Further, the present application claims priority, under 35 U.S.C. §119, of German Patent Application No. 199 14 755.8 filed on Mar. 31, 1999.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to an optical arrangement for symmetrizing the beams from laser diodes.
2. Discussion of Background Information
For the production of high-power laser diode arrangements, a plurality of laser diodes are arranged next to one another in a fixed orientation relative to so-called laser diode bars. Such bars achieve optical output of up to approximately 40W and comprise individual emitters arranged in a row with typical dimensions of the radiating surface from 50 &mgr;m×1 &mgr;m to 200 &mgr;m×1 &mgr;m, with the linear arrangement of these emitters always occurring in the direction of their greatest expansion. In order to achieve even greater outputs, such laser diode bars are stacked on top of one another in the direction of the smaller extension of the emitters into laser diode stacks. The emission of these stacks is extremely asymmetrical and has a low radiance due to the non-radiating regions between the individual emitters of a bar and among the bars as compared to the individual emitters.
In order to achieve a symmetrical bundle with the greatest possible radiance as is needed, for example, for material processing or for pumping of solid state lasers, optical systems are necessary that, on the one hand, cause a symmetrizing of the beams as well as a fading-out of the non-radiating regions for the purpose of maintaining the radiance.
Arrangements for symmetrizing laser diode stacks are known, for example, for connection to optical fibers and/or focusing in a focal spot. Here, depending on the requirements with regard to symmetrizing and radiance, different concepts are prior art.
The coupling of a stack is described in DE 195 00 513 C1. Here, it is disadvantageous that the minimum distance between the individual bars is three times the thickness of the collimation lenses, which may obstruct the integration of as great as possible a number of bars for a given height.
While an arrangement according to DE 195 44 488 does allow a scaling to very high outputs by using many bars, the radiance achieved is at least one order of magnitude less than the fiber-coupled laser diode bars, such as those according to DE 44 38 368.
Moreover, an optical arrangement of multiple laser diodes arranged next to one another in a fixed allocation for symmetrizing of beams is known (DE 196 45 150 A1). The symmetrizing arrangement here comprises a cylinder lens rotated around the optical axis, a directional lens for deflecting the radiation beams of the individual laser diodes, a redirection lens for compensating the deflection of the directional lens, and a subsequent collimation lens.
SUMMARY OF THE INVENTION
The invention provides for an optical arrangement for symmetrizing the beam of a scaleable number of laser diode bars that comprises micro-optic components that are comparably simple to produce, is accessible to a cost-effective miniaturization, and with which the losses in radiance accompanying the symmetrizing are as small as possible. In particular, an improvement of the radiance should be attained as compared to fiber-coupled laser diode bars.
According to one non-limiting aspect of the invention, there is provided an optical arrangement for symmetrizing beams which includes a plurality of laser diodes arranged next to one another. The plurality of laser diodes emit beams which are asymmetrical relative to a first direction and a second direction. The second direction is perpendicular to the first direction. A microcylinder lens optics is arranged in an inclined manner around an optical axis. The beams emitted by the laser diodes in the first direction are collimated and deflected with different angles and are separated thereby. A direction element is arranged downstream of the microcylinder lens optics. The direction element deflects a beam of each individual laser diode in the second direction, whereby each of these beams is deflected by a different angle in the second direction, in such a way that central points of the individual beams converge at a predetermined distance in the second direction. The direction element deflects a beam of the individual laser diode in the first direction in such a way that each of these beams converges at a predetermined distance in the first direction. A redirection element is arranged at a distance downstream of the direction element. The redirection element compensates for different angles of deflection of the beams which are sent through the direction element in a plane.
The plurality of laser diodes may be arranged at least one of one above the other and on a common plane. The plurality of laser diodes may be arranged in a fixed location. The plurality of laser diodes nay be arranged to form a laser diode stack. The optical axis may correspond to an assigned linear array of laser diodes. The microcylinder lens optics may comprise a plurality of microcylinder lenses. The microcylinder lens optics may have sufficient isoplanacy. The redirection element may compensate for different angles of deflection of the beams which are sent through the direction element in a plane defined by the second direction and the optical axis. The first direction may define an “y” axis, the second direction may define an “x” axis, and the optical axis defines a “z” axis. The redirection element may compensate for different angles of deflection of the beams which are sent through the direction element in a plane defined by an x-z plane.
The arrangement may further comprise at least one projection lens arranged between the direction element and the redirection element, whereby the at least one projection lens directs the beams in the second direction to a common focal spot. The arrangement may further comprise at least one optical fiber arranged at the common focal spot. The at least one optical fiber may comprise one of a plurality of optical fibers and a fiber bundle. The microcylinder lens optics may comprise a plurality of microcylinder lenses, at least one of the plurality comprising one of a gradient optical microcylinder lens, a spherical microcylinder lens, an aspherical microcylinder lens, and a Fresnel lens. The microcylinder lens optics may comprise a plurality of microcylinder lenses, each the plurality comprising at least one of a gradient optical microcylinder lens, a spherical microcylinder lens, a aspherical microcylinder lens, and a Fresnel lens. The direction element may comprise at least one of a doublet lens, a biconvex lens, and a planoconvex lens. The direction element may comprise spherical surfaces. The direction element may comprise aspherical surfaces.
The arrangement may further comprise an optical element arranged adjacent the direction element. The optical element may evenly deflect the beams in the second direction in such a way that the beams in first direction are separated from one another at a predetermined distance in the second direction. The optical element may comprise at least one of an array of blazed gratings, a prism stack, and a mirror stack. The optical element may deflect the beams in the second direction by sectioning the direction element and subsequently joining the sections such that they are displaced relative to one another in the second direction. The redirection element may comprise at least one of an array of blazed gratings, a prism stack, and a mirror stack.
The arrangement may further comprise a deflecting element arranged between the direction element and the redirection element. The deflecting element may be arranged adjacent the redirection element, whereby the deflecting element deflects beams in the first direction in such a way that they leave the redirection element parallel to the optical axis. The deflecting element may compr
Göring Rolf
Possner Torsten
Schreiber Peter
Epps Georgia
Fraunhofer-Gesellschaft zur Foerderung der Angewandten Forschung
Greenblum & Bernstein P.L.C.
Thomas Brandi
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