We report the experimental measurements for etch rates of the +z and −z faces of single crystal lithium niobate immersed in HF and HNO₃ acid mixtures of varying ratios. We find that pure HF produces an etch rate that is a factor of 2 higher than the rate obtained for the more frequently used mixture of HF/HNO₃ in a 1∶2 ratio. We further observe that the quality of etching is improved for either pure HF or HF/HNO₃ in a 1∶4 ratio, again by comparison with use of a 1∶2 ratio. These results lead to a discussion of the etch chemistry involved, and an explanation for the observed high degree of differential etching between the +z and −z crystal faces.

In recent years, we have presented results on the development of erasable gratings in silicon to facilitate wafer scale testing of photonics circuits via ion implantation of germanium. Similar technology can be employed to control the operating wavelength of ring resonators, which is very sensitive to fabrication imperfections. Ion implantation into silicon causes radiation damage resulting in a refractive index increase, and can therefore, form the basis of multiple optical devices. In this paper, we discuss design, modeling, and fabrication of ring resonators and their subsequent trimming using ion implantation of germanium into silicon, followed by either rapid thermal annealing or localized laser annealing. The results confirm the ability to permanently tune the position of the resonant wavelength to any point inside the free spectral range of the ring resonator, thus, greatly reducing the amount of power required for active tuning of these devices.

We describe a technique for surface domain engineering in congruent lithium niobate single crystals. The method is based on conventional electric-field poling, but involves an intentional overpoling step that inverts all the material apart from a thin surface region directly below the patterned photoresist. The surface poled structures show good domain uniformity, and the technique has so far been applied to produce domain periods as small as ∼1 μm. The technique is fully compatible with nonlinear optical integrated devices based on waveguide structures.

We report the fabrication of optical channel waveguides in congruent lithium niobate single crystals by direct writing with continuous-wave ultraviolet frequency-doubled ${\mathrm{Ar}}^{+}$ laser radiation (244 nm). The properties and performance of such waveguides are investigated, and first results are presented.