High order modes suppression and manipulation in six-holes helical chiral microstructure fiber

We experimentally report a high-order-mode (HOM) suppression effect which may bring dips in transmission spectrum of a large-size (with core diameter > 10 µm) six-hole helical microstructured fiber (HMSF). Firstly, we performed rigorous theoretical analysis in helical frame to demonstrate that high loss peaks do not appear in fundamental mode. However, this phenomenon suppressed at special wavelengths is due to coupling rather than the interference between HOMs and air filling mode (AFM). For simplicity, we also proposed a more efficient equivalent structure model which may save much time in simulations based on tangential optical fiber analysis. Theoretical results agree well with experimental results. Furthermore, we introduce a method to effectively manipulate the suppression wavelength by rotating the HMSF axially (without changing the fixed structure parameter). Based on several characteristics of HMSF, we also point its potential in applications such as high-energy laser, optical communication, mode filters and so on.