1,721,091 research outputs found
Ferroelectric domain engineering and micro-structuring of lithium niobate
No full textLithium niobate (LN) is a nonlinear optical ferroelectric crystal which is widely used by the photonics industry mainly for the production of ultra-fast optical waveguide modulators (for optical telecoms) and for Quasi Phase Matched (QPM) nonlinear frequency generation. Ferroelectric domain engineering is essential for the fabrication of QPM components but can also play an important role in the performance-improvement of optical modulators [1]. Additionally, ferroelectric domain engineering provides a powerful tool for the surface and bulk micro-structuring of this very important optical crystal when combined with conventional chemical etching. This paper will discuss a number of recently developed all optical and optically assisted methods for ferroelectric domain engineering and the subsequent micro-structuring that may be achieved
UV laser induced ferroelectric domain inversion in lithium niobate single crystals
Full text linkUV radiation in the spectral region beyond ~ 320 nm is strongly absorbed by lithium niobate single crystals. The strong absorption and the consequent localized heating of the crystal triggers physical processes which can affect the state of the material not only by changing the refractive index, as shown in the past, but also by changing its ferroelectric disposition. UV laser irradiation of the polar surfaces in particular can induce or inhibit the inversion of ferroelectric domains. A summary of these UV light induced effects and their utility in the microstructuring of this very important optical ferroelectric crystal will be presented here
Ultra-short light-pulse assisted electric field domain engineering of lithium niobate
No full textWhile several techniques to achieve ferroelectric domain inversion in materials such as lithium niobate (LN) and lithium tantalate (LT) have been successfully demonstrated over the past years, even the 'best' established technique of electric field-induced domain inversion (E-field poling) fails when domain inversion at periodicities of a few microns and below are desired. To overcome the limitations associated with electric field poling, we have been investigating the feasibility of an alternative route, which we refer to as light-assisted E-field poling (LAP)
First-order quasi-phase-matched blue light generation in surface-poled Ti-indiffused lithium niobate waveguides
Full text linkWe demonstrate efficient first-order quasi-phase-matched second-harmonic generation in a surface periodically poled Ti:indiffused lithium niobate waveguide; 6 mW of continuous-wave blue radiation (=412.6 nm) was produced showing the potential of surface domain inversion for efficient nonlinear waveguide interactions
Electro-optically controlled beam switching via total internal reflection at a domain-engineered interface in LiNbO<sub>3</sub>
No full textWe report a novel switching method that occurs due to the electro-optic effect under applied field when a beam incident on an interface between anti-parallel domains in a sample of LiNbO3 subtends an angle greater than that required for total internal reflection (TIR). We present data obtained for wavelengths of 0.543 and 1.52µm and compare this with a theoretical model. This switch has many attractive properties, as TIR is a 100% efficient process leading to the possibility of high contrast ratios; current data shows contrast ratios greater than 100:1 (20 dB). Other properties include relatively simple fabrication procedure, low drive voltages and a wavelength dependence that is less than other electro-optic devices such as Pockels cells
UV laser-induced poling inhibition in proton exchanged optical waveguides in lithium niobate
No full textFerroelectric domain building blocks for photonic and nonlinear optical microstructures in LiNbO<sub>3</sub>
No full textThe ability to manipulate the size and depth of poling inhibited domains, which are produced by UV laser irradiation of the +z face of lithium niobate crystals followed by electric field poling, is demonstrated. It is shown that complex domain structures, much wider than the irradiating laser spot, can be obtained by partially overlapping the subsequent UV laser irradiated tracks. The result of this stitching process is one uniform domain without any remaining trace of its constituent components thus increasing dramatically the utility of this method for the fabrication of surface microstructures as well as periodic and aperiodic domain lattices for nonlinear optical and surface acoustic wave applications. Finally, the impact of multi exposure on the domain characteristics is also investigated indicating that some control over the domain depth can be attained
Holographic recording mechanisms of gratings in indium oxide films using 325nm Helium-Cadmium laser irradiation
No full textUV (325 nm) holographic recording of gratings in indium oxide films fabricated by reactive pulsed laser deposition has been investigated as a function of growth temperature, oxygen pressure and angle of incidence of the plasma plume on the substrate. The influence of the ambient environment (air or vacuum) and the film temperature during recording has also been studied. Large steady state refractive index changes up to 6×10-3 were observed in layers grown at an oblique angle of 75°. About 77% of the magnitude of these changes residues after thermal annealing and is attributed to UV-induced permanent structural rearrangements. In contrast, refractive index changes in films grown at normal incidence were smaller in magnitude and completely reversible
Surface engineered ferroelectric domains in congruent lithium niobate crystals
No full textWe report on the fabrication of high quality, fine period (~1µm) surface ferroelectric domains in congruent lithium niobate single crystals suitable for first order quasi-phase-matched nonlinear interactions in lithium niobate channel waveguides
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