Beam Collimation and Intensity Uniformization of Laser Diode Array Using Lenslets

Abstract

With the advent of the laser, its applications have been extended to many areas including material processing, such as welding, cutting and drilling; and medical procedures, such as eye surgery and cosmetic skin treatments; and other applications such as lithography, semiconductor manufacturing, optical data processing. Among the many kinds, laser diodes have been the most developed in recent years, due to its multiple features like low cost, compactness, electronic compatibility, broad range of wavelengths, and high Pulse Repetition Frequency values. However, the beams from the laser diodes must be shaped before they can be widely used commercially. This is because the beams produced by the laser diodes are characterized as having elliptical beam spot shape along the transverse directions. Also, the intensity profile is Gaussian, not evenly distributed energy profile as commonly preferred in industry applications. In this work, a system that reshapes the beams of an array of laser diodes from elliptical shaped to rectangular shaped and from Gaussian energy distribution to uniform energy distribution. The output beam is also collimated. This system employs 4 sets of lenses, either aspheric, cylindrical or lenslets, which treat the light rays respectively in both perpendicular and parallel planes to achieve the goal. Besides, this lenslet technology used in this system can also be applied to multi laser diode sources to generate a single bunch of high-energy and collimated beam with rectangular beam spot shape. In this way, the disadvantage of the low-energy output of the laser diode will be overcome. In addition, the resultant ray bunches are highly adjustable and can be applied to many more different areas of industrial world. In addition, a detailed derivation process designing the proposed system is shown in this thesis. A series of MATLAB codes are developed to calculate the system parameters according to the derived equations and to simulate the resultant system performance. ZEMAX is also employed to verify the simulation results. A comparison between the simulation results of MATLAB and that of ZEMAX is discussed.