Graphene Covered on Microfiber Exhibiting Polarization and Polarization-dependent Saturable Absorption

Graphene has attracted a lot of research interest, especially as a saturable absorber (SA). However, improvement on thermal damage threshold is critical for the SA. Here, graphene covered on the microfiber is developed for this purpose by use of the light-graphene interaction via the evanescent field of the guided mode in the microfiber. Such interaction is numerically studied by using the theory of the electromagnetic field. Theoretical and experimental results indicate that graphene covered on the upper surface of the microfiber can be used as a polarization-dependent SA as well as an optical polarizer. When the radius size of the microfiber is down to 0.8 μm, its polarization extinction ratio is up to ~27 dB. When the radius of microfiber is up to ~3 μm, a polarization-dependent SA can be obtained with high thermal damage threshold of ~975.82 MWcm^-2 for p -polarization and ~1233.2 MWcm^-2 for s-polarization, and its polarization-dependent modulation depth varies from ~10.25% to ~12.85%.