In applications such as holography, biomedical imaging, aberration correction, laser processing, and free-space optical communication, electronically controlled optical phase modulation has become increasingly popular. At present, there are many technologies that can be used to modulate the optical phase, including the MEMS (Micro-Electro-Mechanical System) and the Liquid Crystal (LC)-based Spatial Light Modulator (SLM). Optical MEMS phase modulators with drivers and micromirrors can be designed to be small in energy consumption and small in size. These advantages allow it to steer a large number of beams simultaneously. However, optical MEMS based phase modulators typically have lower pixel densities than other types of modulators and generally have lower quality control of wavefront aberrations.
In an ideal situation, the SLM has both multi-level (analog) phase modulation and a high frame rate. To this end, Stockley et al. proposed an analog optical phase modulator based on a combination of a ferroelectric liquid crystal layer and a polymer cholesteric liquid crystal in 1995. At this arrangement, the phase variation range is 1.95π. But the applied voltage is highly non-linear.
British researchers have found optical phase modulators based on the uniform electro-optical behavior of collimated chiral nematic liquid crystals based on uniformly arranged helix (ULH, Uniform Lying Helix). Applying an electric field of 4 V / μm at a temperature of 106 ° C, this structure can exhibit a complete 2π phase change and minimal amplitude intensity variation. This structure can be designed into an integrated device for a silicon spatial light modulator. Development has great potential. This research paper was published in the academic journal "NPG Asia Materials" of the Nature Publishing Group.