Optical: systems and elements – Single channel simultaneously to or from plural channels – By surface composed of lenticular elements
Patent
1999-06-21
2000-11-21
Epps, Georgia
Optical: systems and elements
Single channel simultaneously to or from plural channels
By surface composed of lenticular elements
359626, 359627, 359652, 359710, 372 75, G02B 2710, G02B 300, G02B 1318, H01S 3091
Patent
active
061511684
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention concerns an optical assembly for symmetrizing the radiation of laser diodes and more particularly for symmetrizing the radiation of a plurality of laser diodes arranged adjacent to each other in the y-direction in fixed coordination, which radiate in the z-direction and whose radiation in the x-z and y-z planes is asymmetrical, a cylindrical lens system being mounted behind the laser diodes.
2. Description of the Prior Art
To produce high-power laser diode assemblies, a plurality of laser diodes are arranged adjacent to each other in fixed coordination in so-called laser diode bars. Laser diode bars of this kind with optical output power in the region of up to about 30 W usually consist of several laser diodes arranged in a row as individual emitters with geometrical dimensions of the radiating surface between about 50.times.1 mm and about 200.times.1 mm, the linear arrangement of these emitters always being in the direction of their maximum extent. The output radiation of these laser diode bars is extremely asymmetrical. For most practical applications of such laser diode bars, for example for pumping solid-state lasers, for purposes of material processing and medical purposes, a symmetrical beam of high radiance is needed. For wide use of high-power diode lasers in these fields, optical systems as compact as possible are therefore necessary for beam symmetrization.
Assemblies for symmetrizing the radiation of high-power laser diodes using for example special beam rotating elements in the form of prisms are known, whereby the beams emitted by the individual emitters are spatially typically turned through 90.degree. (U.S. Pat. No. 5,168,401, EP 0 484 276). In another arrangement the output radiation of the laser diodes passes through a system of two highly reflective surfaces slightly inclined to each other, in such a way that suitable reconfiguring of the laser diode beam occurs at the output of this system (WO 95/15510). In all cases a largely symmetrical output beam which can easily be focussed is provided.
Disadvantages of these known systems are in particular the complicated nature of the microoptical elements used, this applying in particular to the beam rotation in which realization appears extremely difficult for larger numbers of emitters in the laser diode bar, the high expenditure on adjustment of the whole system and the lack of possibilities of cheap production of such systems.
SUMMARY OF THE INVENTION
Starting from the state of the art, it is the object of the invention to provide an optical assembly for symmetrizing the radiation of a plurality of laser diodes arranged adjacent to each other in fixed coordination, which, using comparatively simple microoptical components, transforms the output radiation without loss of radiance and with improved optical efficiency and at the same time reduction of the dimensions of the assembly. This object is achieved according to the invention by the characterizing features of the main claim in combination with the features of the introductory part.
Due to the fact that a microcylindrical lens with sufficient isoplanasia is arranged in inclined orientation to the laser diode bar, that is, tilted about the optical axis referred to as the z-axis, the output beams of the individual emitters acquire different radiation angles and are thus separated at a long enough distance behind the lens in the desired direction perpendicularly to the direction of the linear assembly of individual emitters. Due to a subsequent optical deflection element which is referred to as the direction element hereafter, the output radiation of the individual laser diodes or emitters is deflected in the direction of the linear assembly of individual laser diodes in such a way that at a predetermined distance behind the direction element the centroids of the beams coincide in this direction. Owing to the fact that furthermore behind the direction element is arranged a second deflection element, referred to hereafter
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Goering Rolf
Possner Torsten
Schreiber Peter
Epps Georgia
Fraunhofer-Gesellschaft zur Foerderung der Angewandten Forschung
Lester Evelyn A.
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