Design and fabrication of a tunable wavelength-selective polarization grating.

Tunable wavelength-selective diffraction with polarization conversion is realized by the design of a liquid crystal (LC) grating containing a twisted nematic alignment structure that is fabricated by an efficient one-step photoalignment method. The diffraction efficiency strongly depends on the wavelength of the incident beam, and this property can be controlled by adjusting the birefringence of the nematic LC using a thermal control. These properties are well described by a theoretical analysis based on the Jones calculus and are experimentally demonstrated using 488, 532, and 633 nm wavelength incident polarized laser beams. The resultant LC grating has potential applications as diffractive optical elements that can simultaneously control the parameters of light such as amplitude, wavelength, and polarization.