Study On Semiconductor Laser Beam Collimating

Owing to its compactness, lightness, and low cost, semiconductor laser play an important role as coherent source in various fields of technology such as military, industry and medicine use and so on . However, the output beam quality of semiconductor laser is poor. Because of the waveguide properties of their active areas, semiconductor lasers generate large divergence-angle beams with elliptically shaped intensity profiles.(FWHM values of a semiconductor laser are 40o and 10o perpendicular and parallel to the junction plane , respectively.) And the beam of semiconductor laser has astigmatism. So , the output beam must be collimated by optical systems in most practical work. Because of simple structure and easy fabricating , the cylindrical lenses have been used in many practical applications for beam collimating of semiconductor lasers.In this paper, according to the basic principle of light– ray propagation, the elliptic cylinder lenses have been designed and used to collimate the semiconductor laser beam. With the computer simulation by use of Matlab, the numerical results are given. The numerical results indicate that the divergence angle of the collimating beam could be as high as 0.1mrad. Both theoretical and numerical results indicate that the advantage of this method is simple structure and easy to design. The results of this paper could be useful for much practical work.