High-precision tracking and dispersion compensation technology based on dual-liquid-crystal-polarization-grating

The dual-liquid-crystal-polarizing-grating system (referred to as dual-grating system) features compact size and light weight, offering significant advantages for replacing traditional turret structures to achieve miniaturization of tracking systems. In beam simultaneous transmit and receive systems, different wavelengths are commonly used to avoid mutual interference. However, due to the grating dispersion effect, beams of different wavelengths exhibit varying deflection angles, leading to the non-coaxial issue between the transmitting and receiving optical axes. This paper investigates high-precision beam tracking technology based on the dual-grating system. We analyze the beam deflection control mechanism and establish a comprehensive dual-grating tracking control model. To address beam deviation at different wavelengths caused by grating dispersion, we propose a dispersion angle compensation method based on a fast steering mirror. A prototype system was constructed to validate tracking and pointing capabilities. Test results demonstrate that our method effectively compensates for the dispersion angle, successfully achieving dynamic tracking and pointing for the dual-grating system while ensuring consistency in beam deflection across different wavelengths. The system achieved a dynamic tracking accuracy of 14.33μrad, a dynamic pointing accuracy of 16.27μrad, and a static pointing accuracy of 4.12μrad. This validates the feasibility of dynamic tracking and pointing technology for dual-grating systems, laying the foundation for the miniaturization of optoelectronic servo systems.