High Power, High Brightness, and Beam Shaping Optics
Apollo Instruments' superior optical technology and quality product line has placed it among the leading companies in today's laser diode market. Achieving high brightness in high-power laser diode beam delivery is a crucial step in the successful and efficient use of high-powered laser diodes in many applications.

The difficulty in accomplishing brightness stems from the geometry and structure of laser diodes. A high-power laser diode is normally found in the form of a laser-diode array (LDA), comprised of a number of emitting elements, with each element being very thin and narrow (about 1x3.5 µm), emitting less than 300 mW. In a typical array, the emitting surface is a narrow line of about 20 segments with multiple emitting elements. Thus, a high-power LDA has a broad-area light-emitting aperture of about 1 cm x 1 µm.

The raw output beam from an LDA is highly divergent and suffers from two asymmetries-astigmatism and an elliptical beam profile. When the noncircular, astigmatic, incoherent beam from the LDA is focused, the beam spot is greatly elongated, which is undesirable for most applications. Also, low brightness of the beam spot results from the "dead" spacing in the emitter configuration.

Apollo Instruments has developed advanced beam-shaping optics in laser diode arrays that can substantially maintain brightness while increasing power output by beam combination. Using various configurations of specialized optical elements that shape and rearrange the beam to achieve high-efficiency and high-power coupling into an optical fiber, a higher quality beam can be realized than traditional beam-shaping and focusing.

With an appropriate focusing optical head, the beam from the fiber can be focused on the work piece or, if necessary, shrunk into a smaller beam spot with an enlarged numerical aperture. This is done by dividing and rearranging the beams from the LDA with two groups of prisms, offset to rearrange the beam with similar BPP in both the slow and fast axis. This advanced beam-shaping optical technology permits for the tremendous success of Apollo Instruments' products that feature high-brightness in high-power laser diode beam delivery.