Quantification of nuclear damage in high energy ion implanted lithium niobate

We show that the approximations used to extract the damage depth profiles from the RBS-channeling spectra of high energy ion implanted lithium niobate lead to incorrect results when two defective regions containing damage generated by electronic and nuclear energy deposition are produced. We demonstrate by high resolution X-ray diffraction analysis that the end-of-range defects formation is not influenced by the onset of different defects in the surface region and it is thus independent of the implantation energy. We propose universal curves, valid for ions Z <= 14, for the end-of-range defective fraction and the maximum strain as a function of the density of energy deposited by nuclear processes

Photoinduced reflectivity oscillation in LiNbO3 crystals irradiated by a KrF laser

A study on LiNbO3 crystal irradiation by pulsed KrF excimer laser beam is presented. The interaction with the 248 nm laser light modifies the material properties so that, when the irradiation is switched off, a time-periodic variation in the material reflectivity, depending on the irradiation conditions, was observed. This phenomenon can be explained in terms of the electro-optic effect induced by the buildup of internal electric fields since the compositional characterization, performed by the secondary ion mass spectrometry, showed no modification in the element concentration and the high resolution x-ray diffraction did not detect any structural deformation within the crystal

Integrated Mach-Zehnder micro-interferometer on LiNbO3

This work presents a scanning micro-interferometer, without moving parts, based on the well-known Mach-Zehnder geometry. The micro-system was obtained by using non-standard processes of planar technology on lithium niobate crystals, in particular the waveguide fabrication was obtained by using high energy ion implantation of medium light mass elements. The scanning effect without moving parts has been obtained by changing the refractive index of the optical waveguides by using electric field. The whole device is 60 mm long with a 0.5 x 1 mm^2 cross section, weights only few grams and its power consumption lies in the milliwatt range. The performances were preliminary tested in the spectral window ranging from 0.4 to 1.0 um. By using standard radiation sources, this micro-system demonstrated a spectral resolution suitable for detecting the characteristic spectral lines of a Xe-arc lamp on a 400 nm wide spectral window. In a further experiment we tested the performances of the microinterferometer for gas trace detection by using a calibrated NO2 optical gas cell. A sensitivity of about 10 ppb for NO2 detection, when suitable optical paths are used, was evaluated

On the dynamics of the damage growth in 5 MeV oxygen-implanted lithium niobate

The damage induced by 5 MeV oxygen ion implantation in x-cut congruent LiNbO3 has been investigated by Rutherford backscattering spectrometry channeling technique. The dynamics of the damage growth has been described by an analytical formula considering the separate contributions of nuclear and electronic energy deposition. It has been hypothesized that the nuclear damage provides the localization of the energy released to the electronic subsystem necessary for the conversion into atomic displacements. The strong influence of the preexisting defects on the damage pileup, foreseen by the analytical formula, has been experimentally verified by pre-implanting the samples with 500 keV oxygen ions. It has been shown that a subsequent 5 MeV oxygen implantation step gives rise to an impressive damage accumulation, eventually leading to the total amorphization of the surface, even at moderate fluences

Effect of low dose high energy O3+ Implantation on the refrective index and linear electro-optic properties in X-Cut LiNbO3: Planar optical waveguide formation and characterization

X-cut LiNbO3 crystals were implanted at room temperature by 5.0 MeV O3+ ions with doses ranging from 1.0x10^14 to 6.0x10^14 O/cm^2. Secondary ion mass spectrometry profiles of atomic species migration as well as damage profiles by the Rutherford backscattering channeling technique and refractive index variation were investigated as a function of dose and subsequent annealing conditions. Two different kinds of damage produced by oxygen implantation were seen: near-surface damage correlated to electronic stopping, which causes an increase of the extraordinary refractive index, and end-of-ion range damage generated by collision cascades, which decreases the extraordinary refractive index values. The different nature of the two kinds of damage is also seen by the different temperature conditions needed for recovery. Low loss planar optical waveguides were obtained and characterized by the prism coupling technique

Structural and compositional characterization of X-cut LiNbO3 crystals implanted with high energy oxygen and carbon ions

High energy implantation of medium-light elements such as oxygen and carbon was performed in X-cut LiNbO3 single crystals in order to prepare high quality optical waveguides. The compositional and damage profiles, obtained by exploiting the secondary ion mass spectrometry and Rutherford back-scattering techniques respectively, were correlated to the structural properties measured by the high resolution X-ray diffraction. This study evidences the devel- opment of tensile strain induced by the ion implantation that can contribute to the decrease of the ordinary refractive index variation through the photo-elastic effect