Either several single emitters (e.g., broad stripe emitters with typical widths of 50 to 500 μm) or diode bars consisting of several equally wide single emitters/broad stripe emitters (e.g., diode bars of typically 10 to 100 equally wide broad stripe emitters with a filling factor of 10 to 95%) can be used for generating efficient and high brilliance diode radiation. For example, diode bars of 30 to 50 emitters each having a width of 100 μm are often used on a bar of 1 cm with a filling factor between 30 and 50%.
The stripe-shaped single emitters of a diode bar each emit a laser beam which propagates in a fast axis (FA) direction in which the beam diverges fast, e.g., with a radiation angle of approximately 50°, and in a slow axis (SA) direction, which is perpendicular to the FA direction, and in which the beam diverges comparatively slowly, e.g., with a radiation angle of approximately 10°. The beam quality in the FA direction is optimum (almost diffraction-limited), whereas the beam quality in the SA direction is relatively poor. In order to combine these individual beams, they are initially collimated in the FA direction by means of a micro-optical cylindrical lens and are subsequently collimated in the SA direction by means of a cylindrical lens array. The beams are subsequently rotated through 90° by means of further micro-optics and are disposed next to each other. The combined laser beam is formed by aligned optical stacking of the laser beam strips emitted by the stripe-shaped single emitters. Since the single emitters are identical, the laser beams emitted from the single emitters each have the same beam parameter product with respect to the SA direction (BPPSA) and the same beam parameter product with respect to the FA direction (BPPFA), the beam parameter product BPP being defined as follows: BPPi=θi*wi (i=SA, FA), where θ is the divergence of the laser beam emitted by the emitter in the SA direction or the FA direction and w is the half width of the emitter in the SA or FA direction.
Aligned optical stacking of the laser beam strips with respectively identical BPPSA and BPPFA results in a combined laser beam that has a beam parameter product which is rectangular or square in the BPPSA-BPPFA-plane and is therefore coupled into a round fiber which has a round beam parameter product in the BPPSA-BPPFA plane, thereby causing radiation losses or incomplete utilization of the fiber.
The document US 2007/0195850 A1 discloses stacking single emitters having different emitter widths in the SA direction on top of each other in the FA direction, thereby adjusting the BPPSA of each emitter to the BPPSA of the associated fiber area. However, handling and positioning of the individual emitters is very complex and this arrangement also requires a relatively large amount of space.
USPTO Backgrounds
USPTO Backgrounds