323,128 research outputs found
UV laser induced ferroelectric domain inversion in lithium niobate single crystals
Get PDFUV 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
Dataset for Optical Gating of Graphene on Photoconductive Fe:LiNbO3
No full textThis file contains the datatset for "Optical Gating of graphene on Photoconductive Fe:LiNbO3" by J. Gorecki, V. Apostolopoulos, J.Y. Ou, S. Mailis, N. Papasimakis.</span
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-assisted fabrication of ridge waveguides in lithium niobate crystals
No full textWe present a UV laser-assisted method for the fabrication of ridge waveguides in lithium niobate. The UV laser irradiation step provides the refractive index change required for the vertical light confinement in the waveguide and also defines the ferroelectric domain pattern which produces the ridge structures after chemical etching
UV laser direct writing of ferroelectric domain inverted structures in single crystal lithium niobate
No full textFerroelectric domain engineering in lithium niobate (LN) is a subject of extensive research mainly for the fabrication of quasi-phase-matched (QPM) nonlinear optical devices but also for the improvement of linear devices and microstructuring. The most common method for ferroelectric domain engineering is by the application of an external electric field, higher than the coercive field (E Here we present UV laser induced inhibition of ferroelectric domain inversion where spatially selective preexposure of the +z face of congruent LN samples inhibits domain inversion in this area upon the application of an external electric field. In these experiments the two steps of i) UV illumination and ii) E-field application are separated; the application of the external electric field can take place long after (days-months) after the UV illumination
Ultraviolet laser-induced submicron spatially resolved super-hydrophilicity on single crystal lithium niobate surfaces
Get PDFLithium niobate crystal surfaces become super-hydrophilic after ultraviolet laser irradiation. The crystal surface hydrophilicity, which was assessed by the contact angle of a sessile drop of de-ionised water, was found to undergo a transition from mildly hydrophobic (contact angle, theta[E] < 50°) to a super-hydrophilic state (theta[E] < 5° ). Patterning of the hydrophilicity at the micron and sub-micron range has been achieved by spatially modulating the illuminating laser beam
Beam deflection and T.I.R. switching in domain-engineered LiNbO<sub>3</sub>
No full textWe have developed a novel electro-optically addressable deflector and switch in a sample of LiNbO3. Patterning and electric-field poling produce areas of oppositely oriented domain regions separated by a sharp boundary. An external electric field applied to this boundary produces equal magnitude refractive index changes, Δn, of opposite sign between adjacent domain regions. For increasing Δn, the incident beam experiences deflection, until a critical value is reached when TIR will occur, thereby leading to complete switching of beam direction. Such a device provides numerous advantages including ease of fabrication, high contrast ratios (TIR is 100% efficient), relatively low drive voltages, large deflections (~8° for an applied field of 1000V), and a wavelength dependence that is superior to other electro-optic devices such as Pockels cells. We will discuss results achieved for light of s and p polarisations, for wavelengths In the visible and the near I.R., with initial contrast ratios >20dB
ByzRev 03.2021.003: Athanassios Mailis, Obscured by Walls. The Bēma Display of the Cretan Churches from Visibility to Concealment: (Byzanz zwischen Orient und Okzident 18). Regensburg: Schnell & Steiner 2020.
No full textAthanassios Mailis, Obscured by Walls. The Bēma Display of the Cretan Churches from Visibility to Concealment (Byzanz zwischen Orient und Okzident 18). Regensburg: Schnell & Steiner 2020. 156 S. – ISBN: 978-3-7954-3560-8 (EUR 39.00
Characterisation of compositional photosensitivity dependence of Ga-La-S thin films fabricated by pulsed laser deposition
No full textThin films of chalcogenide glasses of Ga-La-S composition (GLS) have recently been grown via the technique of pulsed laser deposition (PLD). These non-oxide glasses have many attractive features including a wide transmission range which extends from visible wavelengths up to ~10 micron, and low phonon energies, which drastically reduce non-radiative relaxation rates, thus making them interesting candidates for infra-red laser hosts. Furthermore, under irradiation with light in the blue/uv wavelength region, these glasses can exhibit several photostructural effects including photobleaching, photodoping, and more complicated reconfiguration behaviour, in which refractive index variations of the order of 1% can easily be produced. The exact cause of such index changes is uncertain, but the possibility of writing diffractive grating structures with sub-micron resolution in waveguide GLS structures holds out much potential for distributed feedback integrated optical devices. Previous results on both laser and e-beam grating writing have revealed the ease with which gratings can be produced in GLS films, but so far, no systematic study has been undertaken on how the induced refractive index change depends on exact compositional properties of the GLS glasses
Micro-structuring and ferroelectric domain engineering of single crystal lithium niobate
No full textThe ability to microstructure specific materials is always associated with the ability to selectively remove material over small scale-lengths. Localized etching whether it is chemical or physical, wet or dry, parallel or sequential is central to every modern microstructuring method. For example a beam of accelerated ions is scanned on the surface of interest removing material along its trajectory. Alternatively the surface is prepared/treated in a manner that changes its "quality" locally making it more susceptible or more resistive to a particular etching agent. The whole surface is subsequently exposed to the etching agent which can be a uniform accelerated ion beam, a laser beam or an acid. The etching agent preferentially attacks the pre-treated (or the untreated) portion of the surface removing material. However, before embarking into the description of differential chemical etching of domain-engineered structures we present other methods that have been used for the microstructuring of lithium niobate. The methods listed here have been developed for the microelectronics industry hence they are considered standard and are very well characterized
- …
