Performance comparison between tip-tilt piston deformable mirrors and phase-only light modulators for adaptive MPLCs

Multi-plane light converters (MPLCs), consisting of a series of precisely designed phase masks, can perform unitary beam transformations. Their applications extend from mode-division multiplexing (MDM) to spatial mode sorting and coherent beam combining. Recently, micro electro-mechanical systems (MEMS) mirrors have been suggested for use as tunable phase masks for adaptive MPLCs. In particular, phase-only light modulators (PLMs) have been used to realize adaptive MPLC. We investigate the advantages of using segmented tip-tilt-piston (TTP) deformable mirrors over PLMs. For an equal pixel count and pixel size, segmented TTP deformable mirrors exhibit superior performance for a 15-mode MPLC mode multiplexer, achieving a signal-to-noise ratio (SNR) improvement of over 6 dB and delivering over a 30% improvement in fidelity, as compared to PLMs. More importantly, TTP deformable mirrors can reduce the pixel count by a factor of 16 without sacrificing performance.