Hybrid-integrated polarization mode converters and low-voltage electro-optic modulators using crystal-ion-sliced LiNbO 3 films

Abstract

Lithium Niobate (LiNbO3) films produced by the crystal ion slicing (CIS) method are introduced in various components in use in the optical telecommunications market. The CIS technique employs high-energy ion implantation to create a narrow (~0.2 micrometers ) planar layer of localized damage, buried ~10 micrometers beneath the surface of the implanted LiNbO3 wafers. This sacrificial layer allows for slicing of microns-thick LiNbO3 films, either by selective wet chemical etching or by thermal shock. The obtained films have bulk material properties and morphology suitable for integrated optics applications. Slices of X-cut LiNbO3 were used to produce zero-order wave retarders that can be inserted in slots cut into planar lightwave circuits, resulting in TE-TM polarization mode conversion with high extinction ratio (30 dB) and low excess loss (<0.1 dB). Conventional LiNbO3 waveguide fabrication techniques were combined with the CIS process to produce CIS films of Z-cut LiNbO3 with optical circuits patterned prior to lift-off, having propagation losses typical of bulk LiNbO3 waveguides. Using thin sheets of LiNbO3, velocity- and impedance-matched modulators can be fabricated with low V(pi )L(~7.6 V.cm) and low microwave losses (0.3 db/cm.GHz1/2). The CIS film optical circuits can be integrated into hybrid systems with otherwise incompatible, yet technologically important materials platforms.