Diffractive interferogram-based phase control method of spatial light modulators

As an adaptive optics that can modulate phase of lights, spatial light modulators (SLMs) are widely used in laser shaping, telescopes, and surface figure interferometric tests. The phase control accuracy of SLMs affects the performance of these optical systems. However, the traditional birefringence effects-based phase control method has relatively low accuracy due to the non-linear phase response of SLMs. To this end, a diffractive interferogram-based phase control method is proposed. The general model for describe the diffraction-based phase control method is established. The phase control error model of the diffractive interferogram-based phase control method is analyzed theoretically. Theoretical analysis was conducted to analyze the phase quantization and discretization that influence the phase accuracy. By applying the discretized interference pattern with appropriate quantization level of a given phase and a standard reference phase into the SLM, phase control accuracy can be enhanced up to about λ/30 (λ=632.8 nm) root-mean-square. Comparisons of phase control accuracy of the proposed method with the traditional phase control method are conducted to verify the accuracy enhancement. Using the proposed method, the SLMs can be applied in systems with collimated or divergent beams configuration that requires high phase control accuracy such as interferometric surface figure tests.