Design Method Of A Binary Optical Element For Collimation Of High Power LD Beams With Astigmatism

Owing to its compactness, lightness, and low cost, laser diodes (LD) play an important role as a coherent source in various fields of technology. And it can generate coherent light beams of high power. However, the output beam quality of a LD is poor. Because of the waveguide properties of their active areas, laser diodes generate large divergence-angle beams with elliptically shaped intensity profiles. (FWHM values of a LD are 40°and 10°perpendicular and parallel to the junction plane, respectively.) And the beam of LD has astigmatism. So it is difficult to collimate LD beams effectively.The binary optical elements are small, light, easy to be copied and able to realize multi-purpose integrated, especially suits for the beam shaping of laser diode array.On the basis of summarizing various methods for beam shaping from those reports, and based on accurate far-field model of high-power laser diode, a design method of binary optical element for laser diode beams, which can correct the astigmatism of the laser beam, has been developed, and the principle and process has been given in detail. The method is simple and practical. The relief surface of the element is of multiphase structure. And its theoretical diffraction efficiency is as high as 95 %.The results of this paper could be useful for much practical work.