1,721,072 research outputs found
Microstructuring lithium niobate
No full textLithium niobate is among the most important nonlinear optical materials used today in the photonics industry as it combines a variety of very important optical and electromechanical properties. Microstructuring of this material opens new possibilities for the utility of lithium niobate into a wider range of applications beyond the area of optoelectronics. In this talk a synopsis of methods, developed at the ORC, for the fabrication of refractive, diffractive, nonlinear and actual microstructures on congruent lithium niobate single crystals will be given. The development of such methods shows the potential for using this nonlinear ferroelectric crystal as the base for the development of integrated miniature multifunctional devices
Continuous wave ultra violet laser induced frustration of etching in congruent lithium niobate
No full textSurface relief patterns have been fabricated on the z face of congruent lithium niobate single crystals by illumination of the surface with continuous wave 244 nm laser radiation followed by chemical etching with hydrofluoric acid
UV laser induced surface microstructures in congruent lithium niobate single crystals
No full textUltra violet illumination of the -z face of lithium niobate single crystals, under specific conditions, results in an organized arrangement of submicron etch-resistant features that reflect the illuminating intensity distribution. Consequently, spatially resolved illumination can produce periodic structures with submicron periodicity. Furthermore, a size self-adjustment of the submicron etch resistant features was observed which is related to characteristic lengths (e.g. grating period) of the overall structure. The effect occurs for a narrow range of illuminating intensities and is attributed to a photo-induced electrostatic charge distribution which modifies the electrochemical interaction of the acid with the surface. The size and periodicity of the structures which can be achieved with this method are suitable for the fabrication of 2D photonic crystal structures in this electro-optically tunable material
Switching applications in domain-engineered LiNbO<sub>3</sub>
No full textWe have developed a novel electro-optically addressable total internal reflection (TIR) switch in a sample of z-cut domain-engineered congruent LiNbO3. Electric field poling has been used to domain invert one half of the sample, producing a sharp boundary between the two anti-parallel domain regions. Such a switch has numerous advantages including ease of fabrication, high switching contrast ratios, (TIR is a 100% efficient process for reflection at an ideal interface), relatively low drive voltages, and a wavelength dependence that is less critical than other electro-optic devices such as Pockels cells
Light controlled conductivity of graphene on photorefractive lithium niobate
No full textWe demonstrate non-volatile control by light of electrical conductivity of graphene deposited on iron doped Lithium Niobate (LN)
Efficient blue light generation from surface periodically poled Ti-indiffused channel waveguides
No full textWe report first-order quasi-phase matched blue light generation at 413.17 nm, in a surface-poled Ti-indiffused channel waveguide in lithium niobate. For 70mW of incident c.w. pump, 3.46 mW (uncorrected for reflection losses) was generated at the second harmonic
Electro-optically controlled TIR switching in domain-engineered LiNbO<sub>3</sub>
No full textWe have developed a novel electro-optically addressable total internal reflection (TR) switch in a sample of Limos that has been engineered to have a sharp boundary between two anti-parallel domain regions [1]. Such a switch can provide numerous advantages including ease of fabrication, the possibility of high contrast ratios (TIR is a 100% efficient process), relatively low drive voltages, and a wavelength dependence that is superior to other electro-optic devices such as Pockels cells. The LiNbO3 sample is z-cut, and has been patterned and electric-field poled to produce equal areas of oppositely oriented domain regions. The boundary region should ideally be very smooth, and free from residual poling-induced strain. In our case we observe a static index difference at the boundary, this affects the choice of angle for the grazing incidence beam and hence the contrast achievable experimentally. When an external electric field is applied to this boundary, equal magnitude refractive index changes of opposite sign will occur between the adjacent domain regions. If the value of index change is sufficiently large TIR can occur for the incident beam, thereby leading to switching of beam direction at the boundary from transmission to reflection. A schematic for the switch can be seen below in figure 1. (Schematic of switch.) Light incident on the boundary at an angle that is less than the angle for TIR will be transmitted through it. If however the light is incident on the boundary at angles greater than the TIR angle then it will be reflected with a theoretical efficiency of 100%. As the device consists of anti-parallel regions within a single electro-optic composite crystal the incident beam will only see a change in refractive index when a suitable field is applied. We will discuss results achieved for electro-optically modified reflectivity versus applied electric field, for light of s and p polarisations, and wavelengths in the visible and the near I.R. Initial results have already shown a contrast ratio of greater than 20dB which we expect to be improved with the optimization of annealing, manufacturing and design parameters.To conclude, we have constructed a domain engineered electro-optic total internal reflection switch in a sample of LiNbO3. This novel switching approach can be further improved and optimized, but already shows a good switching contrast ratio and the possibility for practical device implementation
Second harmonic generation via total internal reflection quasi-phase-matching in a hexagonal nonlinear optical microresonator
No full textWe propose the enhancement of the second harmonic generation process in an optical hexagonal microcavity, consisting of a nonlinear material, via total internal reflection quasi-phasematching technique. We present preliminary numerical simulation results showing resonance operation in a suitably designed hexagonally shaped optical microresonator, which demonstrates the operating feasibility of the proposed scheme. The SHG efficiency was calculated using lithium niobate as the nonlinear material. High optical quality hexagonal superstructures can be manufactured routinely by chemical etching of inverted ferroelectric domains in this material
Ultrashort-pulse optically-assisted domain engineering in lithium niobate
No full textUltrashort laser pulses (~150-200 fs) of near-ultraviolet (305 nm) to near-infrared (800 nm) wavelengths have been used to optically-assist domain nucleation and growth in lithium niobate. Within illuminated areas, the electric field required for domain nucleation is reduced by up to 41% in undoped and up to 98% in 5-mol% Mg-doped congruently melting materials, allowing direct-writing of inverted domains with electric fields as small as 100 V mm. A first step towards the formation of optically-defined periodically poled lithium niobate was achieved by illumination via a phase mask, demonstrated over small areas with a period of 5.25 microns
Laser induced organisation and size control of nano-scale etch-resistant features in lithium niobate single crystals
No full textWe report pulsed UV laser-induced organisation of etch-resistant features on the -z face of lithium niobate single crystals, and discuss the formation mechanism and future application areas
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