Polarization control of light transmission through a multimode fiber (Conference Presentation)

Abstract

A multimode fiber subjected to random mode and polarization mixing represents a complex photonic system with strong coupling of spatial, temporal, spectral and polarization degrees of freedom. By exploiting such coupling, we demonstrate a full control of the polarization state of light transmitted through a multimode fiber by adjusting the spatial profile of incident field. After applying stress to the fiber to induce strong mode and polarization mixing, we measure the polarization-dependent transmission matrices, and find the transmission eigenchannels. By launching light to specific eigenchannnels, we are able to preserve the polarization state despite strong polarization mixing in the multimode fiber, or to convert all transmitted light to the orthogonal polarization state. In addition, we show that the linearly polarized input light can be changed completely to circularly polarized output. Furthermore, arbitrary polarization states can be realized for individual spatial channels at the output by tailoring the incident wavefront of a single polarization. Such global control is possible only in the presence of strong mode mixing in the fiber. Namely, strong polarization mixing itself is not sufficient to generate arbitrary polarization states at the output. Therefore, the strong entanglement of spatial and polarization degrees of freedom is essential to achieve a complete control of polarization. Such global control of the polarization states of all output channels is more challenging than the local control of the polarization state of a single output channel.