Diffraction grating with dual modes for two-wavelength rewritable optical pickup heads

This paper discloses the configuration of a dual-mode three-beam grating which adopts the liquid-crystal (LC) modulator technologies and has the function of switching diffraction properties. With the specific design of the top, bottom, and complementary electrodes, the grating has the feature of being modulated by external electric field for generating two diffraction modes. Two modes corresponding to different diffraction directions and angles were verified by experiments. This device could be applied to the fabrication of a monolithic three-beam grating, which is necessary for the tracking detection of a rewritable two-wavelength optical head using a two-wavelength integrated laser diode (TWIN-LD).