Study of beam divergence of a fiber-bundle prism-coupled waveguide using ray tracing

Experimental and theoretical results of a two-stage beam shaping system based on a flexible plastic fiber-bundle and a prism duct are described in this study. An imaging technique is used to investigate the divergence effect on the output beam images and intensity profiles. Photograph pictures of the output beam at different axial distances are taken by a digital camera and the image data is converted into a response curve and presented in this study. According to the experimental results, the propagation in the free space transforms a square beam with a hat-top intensity distribution into a rectangular beam with a conical intensity distribution. For theoretical investigations, using VOB software a simulation is performed to analyze the reported beam shaping design. Ray tracing diagrams are presented to study the direct beam propagation, refracted rays and total reflection rays. The prism duct output beam dimension is determined as a function of distance from the prism exit face and the optimum condition for the maximum power transmission and best image quality is reported. The calculated output beam dimensions by VOB are compared with the experimental ones and there is a good agreement between the observed results.