Efficient light focusing through an MMF based on two-step phase shifting and parallel phase compensating

Based on a parallel phase compensation scheme, we propose an efficient wavefront shaping method using a spatial light modulator (SLM) for quickly generating a series of focused spots through a multimode fiber (MMF). The compensated phase mask obtained by a two-step phase-shifting technique is loaded to the SLM for generating a focused spot at an arbitrary target position out of the fiber facet. Furthermore, the parallel algorithm we present makes it possible to obtain a series of compensated phase masks, which could be used to generate a series of focused spots at different locations. We experimentally obtained 100 tightly focused spots, with an average focused efficiency of 21.60% and an average focused diameter of 1.9240 μm, and only one-time parallel-compensated phase retrieval is required without multiple iteration optimization.