SLM-enabled multi-beam shaping with suppressed grating lobes for point-to-multipoint free-space optical...

Spatial light modulators (SLMs) are extensively utilized for beam steering and multi-beam generation. However, discrete pixel sampling unavoidably introduces spatial aliasing and periodic spectral replication, leading to unwanted grating lobes that degrade beam quality. To address these issues, we propose a two-dimensional auxiliary random phase (2D-ARP) scheme leveraging auxiliary beams and random phase modulation. By redistributing the interference field and reducing the relative concentration of constructive interference, the proposed scheme lowers grating-lobe peak concentration and enhances main-beam energy. Experimental results show an increase of 42.2% in main-lobe energy and a 3.23 dB improvement in peak sidelobe ratio (PSR). A four-beam free-space optical (FSO) communication system, with each beam carrying a 10 GBaud 16-QAM signal, further demonstrates lower bit error rate (BER) and improved receiver sensitivity. Requiring neither hardware modification nor iterative optimization, the proposed scheme is highly attractive for real-time beam shaping and high-capacity multi-beam FSO communications.