In this article the focused beam spot diameter of laser beam is calculated by two methods. The first method witch is the first order approximation is based on investigating the fundamental mode characteristics and its propagation through a thin lens. The second method which is more accurate is based on propagation of the highest TEM_l0 Laguerre-Gauss mode and considering the spherical aberration of coupling thin lens. It was realized that in thin lenses with spherical aberration coefficient more than 10, the effect of spherical aberration on focused beam diameter is significant and due to the importance of choosing the correct fiber coupler diameter, considering this parameter for correct calculation is necessary.

Keywords: Collins integral, Fiber coupling, Gaussian beam, Laguerre-Gauss beam, Spherical aberration

Full-Text [PDF 415 kb]   (394 Downloads)