Adolescence is often characterised by changes in sleep patterns, with reports that the average adolescent does not get the recommended sleep time. Recent qualitative research has identified the use of electronics at bedtime and engagement with social media platforms as barriers to gaining sufficient time and quality of sleep during adolescence. A systematic review and thematic synthesis was undertaken following the three-step thematic synthesis framework. Four databases were searched, and full texts were screened based on pre-existing inclusion/exclusion criteria. Fourteen studies were included, encompassing 967 participants. Three analytical themes were developed: 1) social motivations; 2) habitual smartphone use and 3) recognition of a problem. Findings confirmed how bedtime social media use requires a new framework for recognising the importance of peer relations, where increased frequency and immediacy of communication lays the foundation for social accountability to meet communicative norms and fear of missing out. In the review, adolescents commonly express a lack of control in relation to their social media use which triggered discussion of the habitual aspects of bedtime social media use. The importance of intervention strategies which recognise the wider peer-to-peer social implications of bedtime social media use is discussed with some practical insights offered.

Optical channel waveguides with depressed cladding configurations have been produced in Nd,Gd:CaF2 laser crystals by using ultrafast laser inscription. Waveguide properties are investigated in terms of guiding behaviors and localized laser-induced lattice damages. Under an optical pump of 808 nm light, continuous-wave waveguide lasing at 1.06 mu m is achieved, with a single-mode operation and a minimum lasing threshold of 98.8 mW. Furthermore, the visible emissions of Nd3+ with short wavelengths ranging from 415 nm to 550 nm and long wavelengths from 550 nm to 625 nm are observed upon 808 nm laser excitation via the up-converted process. The intensity ratios of two wavelength ranges are proved to be tunable through changing the pumping polarizations.

We present a cylindrical rod of single-crystal Nd:YAG fabricated from a bulk crystal using femtosecond laser-induced preferential etching. The rod is pumped at 808 nm, and the laser characteristics at 1064 nm emission and the thermal stability are investigated. The slope efficiency was determined with a maximum optical-to-optical efficiency of 7.9%±0.29% and a FWHM linewidth of 299 ± 63 pm. The etched rod shows parameters consistent with existing Nd:YAG gain crystals. This fabrication technology will find use in composite micro-optical devices where microfluidics, active and passive optics, and structures can be etched out of many different materials and combined into a single device.

Trivalent praseodymium (Pr 3+ ) is the most established rare-earth ion for the direct generation of visible light. In our work, based on Pr-doped Lu 3 Al 5 O 12 (LuAG) single crystal, cladding waveguides are fabricated by applying femtosecond laser inscription with different parameters. The main characteristics of the waveguides such as mode distributions, propagation losses are investigated. The investigations on confocal micro-photoluminescence enable us to illustrate femtosecond laser induced modifications in Pr:LuAG matrix. The waveguides are further pumped at a wavelength of 450 nm with an InGaN laser diode. Guided fluorescence emissions in visible range covering green, yellow-green, orange and red are obtained with a maximum slope efficiency of 4 × 10 −4 .

Optical probes operating in the second near-infrared window (NIR-II, 1,000-1,700 nm), where tissues are highly transparent, have expanded the applicability of fluorescence in the biomedical field. NIR-II fluorescence enables deep-tissue imaging with micrometric resolution in animal models, but is limited by the low brightness of NIR-II probes, which prevents imaging at low excitation intensities and fluorophore concentrations. Here, we present a new generation of probes (Ag 2 S superdots) derived from chemically synthesized Ag 2 S dots, on which a protective shell is grown by femtosecond laser irradiation. This shell reduces the structural defects, causing an 80-fold enhancement of the quantum yield. PEGylated Ag 2 S superdots enable deep-tissue in vivo imaging at low excitation intensities (<10 mW cm −2 ) and doses (<0.5 mg kg −1 ), emerging as unrivaled contrast agents for NIR-II preclinical bioimaging. These results establish an approach for developing superbright NIR-II contrast agents based on the synergy between chemical synthesis and ultrafast laser processing.

We report on the fabrication of dual-line waveguides with low propagation losses and single-mode guidance in Pr:CaF2 crystals by applying femtosecond laser inscription. In contrast to the typical highly elliptic modes previously reported in dual-line waveguides, the guiding mode obtained in our work is highly-localized with a near-circular profile at wavelength of 633 nm. The investigations on confocal micro-photoluminescence and micro-Raman imaging enable us to illustrate the effect of different femtosecond laser filamentations on the localized refractive index change in Pr:CaF2 crystals. In company with the mode simulation by finite element method, we further reconstruct the refractive index distribution of the fabricated waveguides. Our results indicate that highly-localized refractive-index increment caused by compressive stress between the lower parts of the filaments is the main mechanism for waveguiding, whereas the damage-induced refractive-index reductions at filaments and in the region between the upper parts of the filaments are responsible for the strong light confinement in both horizontal and vertical directions.

Cladding waveguides are fabricated in Yb,Na:CaF2 crystal by applying femtosecond laser inscription. Waveguide properties are investigated in terms of guiding behaviors and confocal micro-Raman characterizations. In addition, under 946 nm excitation, visible cooperative up-conversion emissions at 478 nm induced by Yb3+ ion pairs are observed while other visible bands are detected owing to the impurities of Er3+ and Tm3+ ions.

There is great potential for microfluidic devices in medical and civil applications. This talk will present work on ultrafast laser inscription for manufacturing microfluidic devices, temperature sensing, cell counting, 3D imaging of cells and biological lasers.

We present research on the development of diode-pumped solid-state lasers suitable for quantum technologies applications at 698.45 nm and 780.24 nm targeting strontium (Sr) and rubidium (Rb) transitions.

We report on an optimized fabrication protocol for obtaining silver nanoparticles on fused silica substrates via laser photoreduction of a silver salt solution. We find that multiple scans of the laser over the surface leads to a more uniform coverage of densely packed silver nanoparticles of approximately 50 nm diameter on the fused silica surface. Our substrates yield Raman enhancement factors of the order of 10 11 of the signal detected from crystal violet. We use a theoretical model based on scanning electron microscope (SEM) images of our substrates to explain our experimental results. We also demonstrate how our technique can be extended to embedding silver nanoparticles in buried microfluidic channels in glass. The in situ laser inscription of silver nanoparticles on a laser machined, sub-surface, microfluidic channel wall within bulk glass paves the way for developing 3D, monolithic, fused silica surface enhance Raman spectroscopy (SERS) microfluidic sensing devices.

Using the ultrafast laser inscription technique. buried channel waveguides have been fabricated in gallium lanthanum sulfide and gallium lanthanum sulfide selenide glasses to demonstrate the suitability of the materials for supercontinuum generation in the mid-IR. Supercontinuum generation was performed using 100 femtosecond pump pulses with micro-Joule pulse energies and a center wavelength of 4.6 mu m, which is in the anomalous dispersion regime for these waveguides. Under such pump conditions. supercontinuum was obtained covering a 25-dB-bandwidth of up to 6.1 um with a long-wavelength edge of 8 mu m. To our knowledge, this represents the broadest and the longest-wavelength IR supercontinuum generated from an ultrafast laser inscribed waveguide to date. Published by The Optical Society under the terms of the Creative Commons Attribution 4.0 License.

Depressed-cladding waveguides are produced in a Yb, Na: CaF2 laser crystal by applying an ultrafast laser inscription. Under pumping at 946 nm, continuous-wave (CW) and Q-switched laser oscillations with low thresholds are realized in these waveguide structures. With the variation of pumping power, switchable single-and dual-wavelength laser emissions peaking at 1013.9 nm and 1027.9 nm are generated. The maximum output power achieved for CW lasing is about 170 mW, corresponding to an optical-to-optical conversion efficiency as high as 45.3%. A pulse energy of 0.13 mu J is obtained for the waveguide laser operating in the pulsed regime. Published by The Optical Society under the terms of the Creative Commons Attribution 4.0 License.

Ultrafast laser inscription has been used to produce channel waveguides in Ge 22 As 20 Se 58 glass (GASIR-1, Umicore N.V).The mode field diameter and waveguide losses at 2.94 μm were measured along with the waveguide dispersion in the 1 to 4.5 μm range, which is used to estimate the zero-dispersion wavelength.Z-scan measurements of bulk samples have also been performed to determine the nonlinear refractive index.Finally, mid-IR supercontinuum generation has been shown when pumping the waveguides with femtosecond pulses centered at 4.6 μm.Supercontinuum spanning approximately 4 μm from 2.5 to 6.5 μm was measured which, to the best of the authors' knowledge, represents the broadest and the deepest IR supercontinuum from an ultrafast laser inscribed waveguide to date.This work, combined with the long wavelength transmission of GASIR-1 up to 15 μm, paves the way for realizing further ultrafast laser inscribed waveguide devices in GASIR-1 for mid-IR integrated optics applications.

Conventional manufacturing of microfluidic devices from glass substrates is a complex, multi-step process that involves different fabrication techniques and tools. Hence, it is time-consuming and expensive, in particular for the prototyping of microfluidic devices in low quantities. This article describes a laser-based process that enables the rapid manufacturing of enclosed micro-structures by laser micromachining and microwelding of two 1.1-mm-thick borosilicate glass plates. The fabrication process was carried out only with a picosecond laser (Trumpf TruMicro 5×50) that was used for: (a) the generation of microfluidic patterns on glass, (b) the drilling of inlet/outlet ports into the material, and (c) the bonding of two glass plates together in order to enclose the laser-generated microstructures. Using this manufacturing approach, a fully-functional microfluidic device can be fabricated in less than two hours. Initial fluid flow experiments proved that the laser-generated microstructures are completely sealed; thus, they show a potential use in many industrial and scientific areas. This includes geological and petroleum engineering research, where such microfluidic devices can be used to investigate single-phase and multi-phase flow of various fluids (such as brine, oil, and CO2) in porous media.

Supercontinuum from 2.5 to 6.5 μm has been generated in ULI waveguides pumped with femtosecond pulses centered at 4.6 μm. Dispersion measurements show the zero dispersion wavelength for the waveguides to be around 5.3 μm.

Silver nanoparticles (Ag-NP) with Surface Enhanced Raman Scattering (SERS) activity were fabricated on a fused silica substrate by ultrafast femtosecond laser photoreduction of a silver salt solution. The SERS effectiveness of the Ag-NP increased with laser writing power and number of scans. SEM images show that the Ag-NP have a more uniform density distribution when using a multi-scan writing technique. A number of different laser parameters were compared, including scan speed, laser power, and number of scans. Overall, it was found that the most effective laser parameters were: 20 µms-1 scan speed, 10 mW laser power and 200 scans. The Ag-NP substrates have been used to detect single bacteria and hold promise to give fast, accurate and specific spectra according to the cell specimen present.

We report on the fabrication via femtosecond laser inscribed of cladding waveguides in Pr:CaF2 crystal. Micro-photoluminescence mapping shows that the original fluorescence properties in the waveguide region are very well preserved.

Microfluidic devices provide a platform with wide ranging applications from environmental monitoring to disease diagnosis. They offer substantive advantages but are often not optimized or designed to be used by nonexpert researchers. Microchannels of a microanalysis platform and their geometrical characterization are of eminent importance when designing such devices. We present a method that is used to optimize each micro-channel within a device using high-throughput particle manipulation. For this purpose, glass-based microfluidic devices, with three-dimensional channel networks of several geometrical sizes, were fabricated by employing laser fabrication techniques. The effect of channel geometry was investigated by employing an optical tweezer. The optical trapping force depends on the flow velocity that is associated with the dimensions of the microchannel. We observe a linear dependence of the trapping efficiency and of the fluid flow velocity, with the channel dimensions. We determined that the highest trapping efficiency was achieved for microchannels with aspect ratio equal to one. Numerical simulation validated the impact of the device design dimensions on the trapping efficiency. This investigation indicates that the geometrical characteristics, the flow velocity, and trapping efficiency are crucial and should be considered when fabricating microfluidic devices for cell studies. (C) 2017 Society of Photo-Optical Instrumentation Engineers (SPIE)

Three-dimensional cellular imaging techniques have become indispensable tools in biological research and medical diagnostics. Conventional 3D imaging approaches employ focal stack collection to image different planes of the cell. In this work, we present the design and fabrication of a slanted channel microfluidic chip for 3D fluorescence imaging of cells in flow. The approach employs slanted microfluidic channels fabricated in glass using ultrafast laser inscription. The slanted nature of the microfluidic channels ensures that samples come into and go out of focus, as they pass through the microscope imaging field of view. This novel approach enables the collection of focal stacks in a straight-forward and automated manner, even with off-the-shelf microscopes that are not equipped with any motorized translation/rotation sample stages. The presented approach not only simplifies conventional focal stack collection, but also enhances the capabilities of a regular widefield fluorescence microscope to match the features of a sophisticated confocal microscope. We demonstrate the retrieval of sectioned slices of microspheres and cells, with the use of computational algorithms to enhance the signal-to-noise ratio (SNR) in the collected raw images. The retrieved sectioned images have been used to visualize fluorescent microspheres and bovine sperm cell nucleus in 3D while using a regular widefield fluorescence microscope. We have been able to achieve sectioning of approximately 200 slices per cell, which corresponds to a spatial translation of ∼ 15 nm per slice along the optical axis of the microscope.

We report on efforts to improve the lifetime of biological lasers through the use of ascorbic acid (also commonly known as vitamin C). Fluorescent proteins and dyes, used in biological lasers, suffer from photobleaching due to the build-up of reactive oxygen species (ROS) which causes damage leading to a decrease in emission over time. This is an issue both for laser lifetime and cell health. It has previously been shown that ascorbic acid can be effective in reducing ROS levels in a variety of applications. For our experiments human embryonic kidney cells (HEK293), containing the fluorescent dye Calcein AM, were placed between two dielectric plane mirrors to form a laser cavity. The cells were pumped using the output of a Ti:Sapphire femtosecond OPO system, frequency doubled twice in BBO crystals, giving an output of 474 nm. Initial results have shown an increase in laser lifetime when ascorbic acid is added to cells indicating a reduction in the build-up of ROS.