In this paper we present an active GRadient-INdex (GRIN) beam shaper with gain for Gaussian to flat-top beam conversion. This extra-cavity beam shaper is based in the proper design of an active GRIN selfoc rod microlens in order to perform the beam shaping operation. General condition for obtaining beam shaping by active GRIN rod microlenses is shown. Irradiance evolution through the active material for a laser beam operating at 1550 nm and 1.25 mm beam half-width is simulated and the shaping length in each case is determined. The active GRIN beam shaper is sensitive to deviations from design laser parameters such as wavelength and beam diameter, what can have great influence on the output flat-top beam quality. Variations on the design length of the shaper due to fabrication process errors can also emerge on unwanted output irradiance profiles. Here we analyze the sensitivity of the active GRIN beam shaper to the wavelength and beam half-width of the input Gaussian beam, as well as to the length of the GRIN rod lens in order to design a beam shaper that meets requirements within an acceptable tolerance. In this way, flatness quality of the output irradiance profile is examined. For the active beam shaper reported, microlens thickness, input wavelength and beam half-width tolerances are 10%, 10% and 5%, respectively.

Date Published: 18 November 2013
PDF: 8 pages
Proc. SPIE 8785, 8th Iberoamerican Optics Meeting and 11th Latin American Meeting on Optics, Lasers, and Applications, 87854R (18 November 2013); doi: 10.1117/12.2026225

Published in SPIE Proceedings Vol. 8785:
8th Iberoamerican Optics Meeting and 11th Latin American Meeting on Optics, Lasers, and Applications
Manuel Filipe P. C. Martins Costa, Editor(s)