1,963 research outputs found
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
Latent ultrafast laser-assisted domain inversion in congruent lithium niobate
No full textThe combination of light with external electric fields has been successfully used for the domain engineering of ferroelectric lithium niobate crystals [1,2]. It has been shown that whereby the application of the electric field is delayed with respect to the illumination of the crystal. Furthermore, the local coercive field reduction becomes fixed after the first poling cycle. Hence, the initially illuminated and domain inverted regions will re-invert at lower voltages for subsequent poling cycles. The most significant implication of the latency is the decoupling of the laser illumination and E-field application steps which significantly simplifies the experimental setup and allows for high resolution light patterning, e.g. using a phase mask
Electro-optic solid state beam deflection: resolution considerations and 2-D implementation
No full textA simpler, alternative to 'prism type' electro-optic (EO) solid state deflectors has been recently demonstrated. This device is essentially a single interface version of a conventional deflector, but significant deflection is achieved by setting the input beam at grazing incidence to the interface (where, additionally, it can act as an EO switch). The increased deflection seen near TIR is, however, made at the expense of increased divergence of the output beam. Overall deflection can be a misleading quantity to determine the performance of a deflector as this could always be increased with suitable lenses. A more reliable figure of merit is the number of separate resolvable spots that can be imaged from the deflector output. Here we analyze the achievable resolution for a single interface deflector. It can be seen that with a suitably sized device, significant resolution can be attained from a single interface deflector as shown in Fig.1. The resolution is shown here as a function of temperature since if the deflector were to be working at visible wavelengths if would necessarily be heated to avoid photo-refractive effects. Additionally heating has a secondary role in increasing resolution due to the intrinsic n term in the EO equation. Although there are still issues to overcome in terms of the output beam quality of a single interface deflector, it does possess one major advantage over the previous, multiple interface deflectors. Due to its simplicity it can be fashioned to function in 2 dimensions (Fig.2). This would be the first ever report to our knowledge of a 2D EO solid state beam deflector
Ultrashort-pulse optically-assisted domain engineering in lithium niobate
No full textUltrashort laser pulses (120-150 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
Microstructuring lithium niobate: towards new hybrid devices
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 properties which, apart from the optical nonlinearity, includes electrooptic, pyroelectric, piezoelectric behaviour and an optical transparency which extends from the UV (350nm) to the infrared (5µm) spectral region. In order to benefit from both the optical and electro-mechanical properties of lithium niobate it is necessary to develop methods for the fabrication of suitable surface and/or bulk structures depending on the application involved. Such methods for surface and bulk microstructuring have been developed and are presented here aiming to show that there is significant scope for the broadening of the utility of this very useful material.
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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
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
Etch frustration in congruent lithium niobate single crystals induced by femtosecond ultra-violet laser irradiation
No full textModification of the chemical etching behaviour of undoped congruent z-cut lithium niobate single crystals is achieved by pre-illumination of the -z face of the crystal with sub-ps ultraviolet laser radiation at 248 nm, at energy fluences below the threshold for ablation. A systematic study of the effect of the energy fluence and total exposure on the etch frustration is presented
Capillary-based reverse transcriptase loop-mediated isothermal amplification for cost-effective and rapid point-of-care COVID-19 testing
No full textAs the SARS-CoV-2 pandemic continues to spread, the necessity for rapid, easy diagnostic capabilities could never have been more crucial. With this aim in mind, we have developed a cost-effective and time-saving testing methodology/strategy that implements a sensitive reverse transcriptase loop-mediated amplification (RT-LAMP) assay within narrow, commercially available and cheap, glass capillaries for detection of the SARS-CoV-2 viral RNA. The methodology is compatible with widely used laboratory-based molecular testing protocols and currently available infrastructure. It employs a simple rapid extraction protocol that lyses the virus, releasing sufficient genetic material for amplification. This extracted viral RNA is then amplified using a SARS-CoV-2 RT-LAMP kit, at a constant temperature and the resulting amplified product produces a colour change which can be visually interpreted. This testing protocol, in conjunction with the RT-LAMP assay, has a sensitivity of ∼100 viral copies per reaction of a sample and provides results in a little over 30 min. As the assay is carried out in a water bath, commonly available within most testing laboratories, it eliminates the need for specialised instruments and associated skills. In addition, our testing pathway requires a significantly reduced quantity of reagents per test while providing comparable sensitivity and specificity to the RT-LAMP kit used in this study. While the conventional technique requires 25 μl of reagent, our test only utilises less than half the quantity (10 μl). Thus, with its minimalistic approach, this capillary-based assay could be a promising alternative to the conventional testing, owing to the fact that it can be performed in resource-limited settings, using readily available apparatus, and has the potential of increasing the overall testing capacity, while also reducing the burden on supply chains for mass testing
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