Abstract

An optical switch based on thick phase-reflective gratings and optical waveguides has been designed and tested. As a switch, the device offers both speed and high isolation. The switching mechanism relies on modulation of the grating diffraction efficiency by locally varying the average refractive index within the grating region of the waveguide. Electro-optic modulation of holographic phase gratings recorded in bulk LiNbO₃ has been demonstrated previously.¹ The performance of the bulk device, however, encounters severe limitations that are overcome by the waveguide design. In the waveguide configuration, gratings with thicknesses of more than 100 m can be fabricated. These gratings are capable of 100% diffraction efficiency and exhibit spectral bandwidths of only a few angstroms. The diffraction efficiency of such gratings is easily varied by addressing with a tunable narrow-spectral-bandwidth source or, alternatively, by locally varying the average refractive index within the grating region. The latter requires index differences of only 10⁻⁴10⁻³. The experimental device described in this presentation used LiNbO₃ and the linear electro-optic effect, although other active and passive mediums may be used. In addition to switching elements, modulators and grating based logic elements have also been designed.

© 1990 Optical Society of America