Abstract: A groove is disposed in a substrate longitudinally along the outside radius of a bent integrated optical waveguide to constrain the mode of optical energy propagating therein such that the optical energy that would normally be radiated is confined to the waveguide, thereby reducing transmission loss through the bend. Further, to reduce coupling loss between an integrated optical waveguide and an optical fiber, two grooves are disposed longitudinally along either side of the integrated optical waveguide to constrain the mode of optical energy propagating in the waveguide to approximate the mode of the optical energy propagating in the optical fiber. To further reduce both bend and coupling losses, the ends of the grooves bend away from the waveguide.

Abstract: A laser or other source of radiant electromagnetic energy removes optically transparent material (e.g., LiNbO.sub.3) to form various structures. To enhance coupling the radiant energy to the optical material, a layer of an ablative absorber (e.g., a metal or organic material) can be used. Alternately, the radiant source can be initially operated above a threshold that causes removal of a surface layer of the optical material. After selectively thus removing a surface layer of the optical material, subsequent sub-threshold applications of radiant energy remove additional optical material due to a change in the underlying material, rendering it more absorptive at the wavelength of the electromagnetic energy. Optical devices, including waveguides, can be formed, as well as isolation grooves, alignment structures, etc.

Abstract: The specification describes a technique for etching titanium using EDTA compounds. It is especially useful for selective etch processes such as those used to form titanium diffused waveguides in lithium niobate crystals.