High-precision beam tracking using liquid crystal spatial light modulator based on spatially partitioned...

The liquid crystal spatial light modulator (LCSLM) represents a promising solution for next-generation pointing, acquisition, and tracking (PAT) in space laser communication, owing to its non-mechanical steering, compact form factor, low power consumption, and programmable phase control capability. However, the inherent viscosity of liquid crystal molecules fundamentally limits the achievable response bandwidth of the device. Under high-frequency disturbances or rapid relative motion, this limitation frequently induces transient phase distortions and power fluctuations, potentially leading to link loss. To address these challenges, this paper proposes a spatially partitioned time-interleaved (SPTI) phase updating strategy. By dividing the optical aperture into sub-apertures with staggered updates, the proposed strategy disperses the concentrated transient errors typical of full-scale synchronized updates across spatiotemporal domains, thereby significantly enhancing the equivalent control bandwidth. We developed a spatiotemporal phase evolution model for the LCSLM and validated the approach through comprehensive simulations and experiments. Results demonstrate that, compared to the conventional updating strategy, the SPTI strategy improves the tracking accuracy by 40%, suppresses the received optical power fluctuations by 60%, and enables error-free 10 Gbps communication within a 10° angular range. These results confirm that the proposed strategy effectively alleviates the dynamic bandwidth limitations of liquid crystal devices and substantially extends their operational envelope in high-dynamic space laser communication scenarios.