Switchable Wave Plate Research Articles

Tunable dielectric metasurfaces by structuring the phase-change material

Metasurfaces have made great progress in the last decade for generating miniature and integrated optical devices. The optical properties of metasurfaces can be tuned dynamically by integrating with phase-change materials. However, the efficiency of tunable metasurfaces remains a bit low, which is a disadvantage for the realistic applications of metasurfaces. Here, we demonstrate the tunable dielectric metasurfaces by structuring the phase-change material Ge2Sb2Te5. The unit cell of metasurface is composed of several Ge2Sb2Te5 nanopillars with different geometric parameters, and the incident light interacts with different nanopillars at diverse phases of Ge2Sb2Te5, leading to various functions. By elaborately arranging the Ge2Sb2Te5 nanopillars, various tunable optical devices have been realized, including tunable beam steering, reconfigurable metalens and switchable wave plate. The refractive direction, focal length and polarization state can be tuned through the phase transition of Ge2Sb2Te5. The phase-change metasurfaces based on Ge2Sb2Te5 nanostructures could be used in cameras, optical microscopy and adaptive optics.

Proposal for Rewritable Microholographic Recording Using Polarization-Sensitive Materials

Rewritable microholographic recording using polarization-sensitive materials has been proposed. Two types of optical configuration (i.e., single-channel detection and differential detection) have been presented. Recording operation is carried out by focusing two light beams with orthogonal polarization states in the recording medium. The polarization states of the two light beams are switched with switchable waveplates according to recording signal. The polarization directions of light in which the two light beams are synthesized are recorded in the recording medium as a polarization diffraction grating. Readout operation is carried out by focusing a light beam with a certain polarization state in the recording medium. A reflected light beam from the polarization diffraction grating is detected by a photodetector. The readout signal is obtained from the intensity or the polarization state of the reflected light beam. This technology features not only rewritability but also overwritability. Readout signal simulation considering polarization has demonstrated the validity of this technology.

Proposal for Rewritable Microholographic Recording Using Polarization-Sensitive Materials

Rewritable microholographic recording using polarization-sensitive materials has been proposed. Two types of optical configuration (i.e., single-channel detection and differential detection) have been presented. Recording operation is carried out by focusing two light beams with orthogonal polarization states in the recording medium. The polarization states of the two light beams are switched with switchable waveplates according to recording signal. The polarization directions of light in which the two light beams are synthesized are recorded in the recording medium as a polarization diffraction grating. Readout operation is carried out by focusing a light beam with a certain polarization state in the recording medium. A reflected light beam from the polarization diffraction grating is detected by a photodetector. The readout signal is obtained from the intensity or the polarization state of the reflected light beam. This technology features not only rewritability but also overwritability. Readout signal simulation considering polarization has demonstrated the validity of this technology.