TY - JOUR T1 - Estimation of focused beam spot size for a multimode laser by considering spherical aberration of lens TT - تخمین قطر باریکه لیزر چندمدی کانونی شده توسط عدسی تزویجگر برای باریکه‌های با تقارن محوری با لحاظ ابیراهی کروی عدسی JF - opsi JO - opsi VL - 26 IS - 0 UR - http://opsi.ir/article-1-2017-en.html Y1 - 2020 SP - 221 EP - 224 KW - Collins integral KW - Fiber coupling KW - Gaussian beam KW - Laguerre-Gauss beam KW - Spherical aberration N2 - 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 TEMl0 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. M3 ER -