A computer-generated hologram (CGH) designed using the iterative Fourier transform algorithm was recorded in a cell filled with a polymer-dispersed liquid crystal material under a collimated He–Ne laser beam operating at 543nm. Due to the photopolymerization induced phase separation, an index modulation was formed between the polymer-rich and liquid-crystal-rich regions. The results showed a good reconstructed image. With a suitable voltage applied, the reconstructed image can be erased due to the index change between the polymer and liquid crystal. Such electrically switchable CGH is potentially useful in information storage and adaptive optical elements.
An electrically tunable optical vortex was generated in an antiparallel liquid crystal cell, where one electrode was patterned by a photomask, which is achieved by transferring a computer-generated hologram onto a transparency with a resolution of about 25 m. When a voltage was applied on the cell, an index modulation was induced due to the realignment of liquid crystal molecules, and then an optical vortex beam was produced. The diffraction efficiency measured was about 27.5%. The device also showed a reasonably fast response time.
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