梯度折射率光纤透镜的薄透镜等效分析

Analysis of the Graded-index Fiber-lens Using Thin Lens Equivalent

从等效薄透镜的角度对热扩束(TEC)光纤+无芯光纤+梯度折射率(GRIN)光纤透镜进行了细致的理论分析,其中TEC光纤调整输入高斯光束的束腰半径,无芯光纤控制束腰和薄透镜间的距离,GRIN光纤两主面之间部分等效为薄透镜,其焦距由光纤的折射率分布参数g决定。推导了出射高斯光束的束腰半径和工作距离的解析表达式,进而对该光纤透镜做了数值模拟,讨论了无芯光纤和GRIN多模光纤的长度对光纤透镜参数的影响。当GRIN光纤透镜用作准直器使用时,其最大束腰直径可达到80μm,可将单模光纤的远场发散角压缩8倍;用于MEMS器件时,最大工作距离可达到3 mm。

The theoretical analysis of the TEC ＋ coreless ＋ graded-index（GRIN） style fiberlens was particularly by thin lens equivalent method expatiated in this paper. TEO part affected Gaussian beam waist radius, Ooreless part worked on the space between beam waist and thin lens,and GRIN part acted as thin lens, in which focal length was determined by fiber index distribution parameter g. In addition, analytic expression of the waist spot size and working distance of output Gaussian beam were derived, and the influence of coreless fiber and GRIN fiber＇s length upon fiber-lens parameter was discussed by numerical simulation results. When a GRIN style fiber-lens is regarded as a collimator,the maxi- mum of waist spot diameter can be close to 80 lam, and the divergence angle of singlemode optical fiber can be reduced 8 times. When it is applied to MEMS device,the maximum of working distance can approach to 3 mm.