Accurate Measurement And Characterization Of Phase Modulation Characteristics Of LCoS

Silicon based liquid crystal spatial light modulator(LCoS-SLM)has been widely used for phase modulation,owing to its advantages of high spatial resolution,low power consumption,and independent addressing capability.Recently,the requirements for wavefront control precision are more stringent with the improvement of application.The wavefront modulation performance of LCoS-SLM,such as phase response rate,phase modulation precision and phase modulation accuracy,will directly affect whether it can meet the requirements of application scenarios.In this paper,the phase jitter and fringing field effect in the LCoS-SLM were studied and characterized in the temporal and the spatial domain.The main contents are as follows:(1)The causes of phase jitter in time domain and fringing field effect in space domain were analyzed by the structure of the liquid crystal spatial light modulator,the driving mechanism,and the response process of liquid crystal molecules.(2)The physical model of LCoS was built by MATLAB Simulink,and the effects of frame rate and gray levels on phase jitter were simulated and analyzed.The time-domain waveform of LCoS-SLM phase modulation was experimentally characterized.Its spectral analysis verified that the phase jitter frequency under different gray levels is consistent with the frame rate of the device,while the jitter amplitude is different.Subsequently,the periodic jitter of phase modulation was mathematically characterized by Fourier series.(3)The finite difference iteration method was developed to calculate the liquid crystal molecular director distribution and potential distribution in LCoS,and the fringing field effect of LCoS-SLM was discussed theoretically.The optical path of fringing field effect measurement was built based on the principle of polarization interference.The spatial phase change of LCoS-SLM phase modulation was measured experimentally.The results show that the relation between the flyback width and the phase difference of adjacent pixels conforms to the cubic function.The phase distribution of LCoS under the fringing field effect was calculated by the approximate analysis model of the point spread function,and the root mean square error between the calculated value and the experimental value was less than 0.0148?.