Simultaneous Generation of the First- and Second- Order OAM Using the Cascaded HLPGs

A new method enabling the simultaneous generation of the first- and the second-order orbital angular momentum (OAM) modes has been proposed and experimentally demonstrated, which is realized by using two consecutively- cascaded helical long-period fiber gratings (HLPGs). As a typical example, the first-order (l = 1) OAM mode with a conversion efficiency of 94% and the second-order (l = -2 ) OAM mode with a conversion efficiency of 83% have been successfully obtained. This is the first report for simultaneous generation of the first- and second-order OAM modes by using the HLPGs only. The proposed method may provide a new way to realize multiple OAM modes in a fiber.