Generation of Tunable Broadband OAM Beams in Large Ring Core Multimode Fibers

The generation of beams carrying orbital angular momentum (OAM) has attracted widespread attention because of the many potential applications in microscopy, imaging, quantum optics and communications. One common approach to generate OAM beams is to use using free-space optics such as phase waveplates or spatial light modulators (SLM) [1], but these methods are often hindered by relatively low efficiency, limited bandwidth, or power. The use of optical fibers with ring cores has been explored for transmitting OAM beams over long distances [2]. More recently, it has also been shown that nonlinear dynamics in those fibers can further transfer the OAM properties of a pump beam to new wavelengths [3], [4]. However, this requires light to be injected (using e.g. a SLM) with amplitude and phase profiles matching that of the OAM mode supported by the fiber. Furthermore, ring core fibers are generally designed with a small core to support a small number of modes and avoid crosstalk, which limits the topological charge tunability.