Search

Passive daytime radiative coolers (PDRCs) with exceptionally high solar reflectance and emissivity in the atmospheric window can provide sub-ambient cooling while reducing buildings' cooling energy demand. However, glare and esthetic issues limit their application to high-rise buildings while may increase the building's heating energy needs. Passive colored radiative coolers (PCRCs), based on fluorescent materials, convert part of the absorbed UV and visible solar radiation into emitted light, providing color and reducing the thermal balance of the materials and the potential visual annoyance. This article investigates the state of the art on the PCRC based on fluorescent technologies. Seven articles presenting different combinations of PDRC technologies with fluorescent components to create PCRCs of various colors are presented and analyzed in detail. Quantum dots and phosphors embedded in polymer matrices and combined with reflecting and emitting layers were used as the fluorescent layer of the seven developed green, red, yellow, and yellow–green films. The proposed PCRCs are characterized by very significant differences in cooling performance, although most presented sub-ambient surface temperatures. Their cooling potential is comparatively investigated in terms of the testing climatic conditions and their optical characteristics. The potential increase of their surface temperature, caused by the addition of the fluorescent component, is analyzed through comparisons between the proposed PCRCs and the corresponding white PDRCs without the fluorescent component. The average temperature difference of the green, red, yellow, and yellow–green films against the reference PDRCs is found to be 0.66 °C, 2.6 °C, 1.7 °C and 1.4 °C, respectively. A relevant decreasing trend, but not statistically significant, is observed between the temperature increase caused by the fluorescent additives and the corresponding photoluminescence quantum yield. [ABSTRACT FROM AUTHOR]

Whilst it is now well recognized that some natural surfaces such as seemingly fragile insect wings possess extraordinary antimicrobial properties, a quest to engineer similar nanopatterned surfaces (NPSs) is ongoing. The stake is high as biofouling impacts critical infrastructure leading to massive social and economic burden with an antimicrobial resistance (AMR) issue at the forefront. AMR is one of the most imminent health challenges the world is facing today. Here, in the effort to find more sustainable solutions, the NPSs are proposed as highly promising technology as their antimicrobial activity arises from the topographical features, which could be realized on multiple material surfaces. To fully exploit these potentials however, it is crucial to mechanistically understand the underlying killing pathways. Thus far, several mechanisms have been proposed, yet they all have one thing in common. The antimicrobial process is initiated with bacteria contacting nanopatterns, which then imposes mechanical stress onto bacterial cell wall. Hence, the activity is called "mechano-bactericidal". From this point on, however, the suggested mechanisms start to diverge partly due to our limited understanding of force interactions at the interface. The aim of this mini review is to analyze the state-of-the-art in proposed killing mechanisms by categorizing them based on the characteristics of their driving force. We also highlight the current gaps and possible future directions in investigating the mechanisms, particularly by shifting towards quantification of forces at play and more elaborated biochemical assays, which can aid validating the current hypotheses. [ABSTRACT FROM AUTHOR]

The electrochemical synthesis of hydrogen peroxide (H2O2) via a two‐electron (2 e−) oxygen reduction reaction (ORR) process provides a promising alternative to replace the energy‐intensive anthraquinone process. Herein, we develop a facile template‐protected strategy to synthesize a highly active quinone‐rich porous carbon catalyst for H2O2 electrochemical production. The optimized PCC900 material exhibits remarkable activity and selectivity, of which the onset potential reaches 0.83 V vs. reversible hydrogen electrode in 0.1 M KOH and the H2O2 selectivity is over 95 % in a wide potential range. Comprehensive synchrotron‐based near‐edge X‐ray absorption fine structure (NEXAFS) spectroscopy combined with electrocatalytic characterizations reveals the positive correlation between quinone content and 2 e− ORR performance. The effectiveness of chair‐form quinone groups as the most efficient active sites is highlighted by the molecule‐mimic strategy and theoretical analysis. [ABSTRACT FROM AUTHOR]

The electrochemical synthesis of hydrogen peroxide (H2O2) via a two‐electron (2 e−) oxygen reduction reaction (ORR) process provides a promising alternative to replace the energy‐intensive anthraquinone process. Herein, we develop a facile template‐protected strategy to synthesize a highly active quinone‐rich porous carbon catalyst for H2O2 electrochemical production. The optimized PCC900 material exhibits remarkable activity and selectivity, of which the onset potential reaches 0.83 V vs. reversible hydrogen electrode in 0.1 M KOH and the H2O2 selectivity is over 95 % in a wide potential range. Comprehensive synchrotron‐based near‐edge X‐ray absorption fine structure (NEXAFS) spectroscopy combined with electrocatalytic characterizations reveals the positive correlation between quinone content and 2 e− ORR performance. The effectiveness of chair‐form quinone groups as the most efficient active sites is highlighted by the molecule‐mimic strategy and theoretical analysis. [ABSTRACT FROM AUTHOR]

Diffractive optical elements such as periodic gratings are fundamental devices in X‐ray imaging – a technique that medical, material science, and security scans rely upon. Fabrication of such structures with high aspect ratios at the nanoscale creates opportunities to further advance such applications, especially in terms of relaxing X‐ray source coherence requirements. This is because typical grating‐based X‐ray phase imaging techniques (e.g., Talbot self‐imaging) require a coherence length of at least one grating period and ideally longer. In this paper, the fabrication challenges in achieving high‐aspect ratio nanogratings filled with gold are addressed by a combination of laser interference and nanoimprint lithography, physical vapor deposition, metal assisted chemical etching (MACE), and electroplating. This relatively simple and cost‐efficient approach is unlocked by an innovative post‐MACE drying step with hexamethyldisilazane, which effectively minimizes the stiction of the nanostructures. The theoretical limits of the approach are discussed and, experimentally, X‐ray nanogratings with aspect ratios >40 are demonstrated. Finally, their excellent diffractive abilities are shown when exposed to a hard (12.2 keV) monochromatic X‐ray beam at a synchrotron facility, and thus potential applicability in phase‐based X‐ray imaging. [ABSTRACT FROM AUTHOR]

Background: Hepatic dysfunction in patients with classical Hodgkin lymphoma (cHL) is of multifactorial aetiology. Prompt evaluation with laboratory tests and imaging methods is sufficient for diagnosis in most cases. Intrahepatic cholestasis and vanishing bile duct syndrome (VBDS) may complicate cHL as rare paraneoplastic phenomena. Liver biopsy provides crucial evidence of cholestasis, and ductopenia, if present, confirms the diagnosis of VBDS. Case Report: We report on a cHL patient that presented with jaundice and bulky mediastinal disease and unfold the therapeutic dilemmas we confronted. Marked hyperbilirubinemia was successfully reversed with brentuximab vedotin (BV) at a dose of 1.2 mg/kg and the patient was subsequently treated with doxorubicin, bleomycin, vinblastine and dacarbazine (ABVD) at full doses, achieving complete metabolic response. A literature review of intrahepatic cholestasis in cHL is also presented based on currently available data with focus on treatment options and clinicopathologic associations. Conclusion: VBDS and intrahepatic cholestasis are rare and potentially fatal complications of cHL. Their prompt recognition and appropriate treatment can dramatically affect cHL patients' outcome. BV, used at a reduced dose as a bridging therapy, should be considered as a high-priority treatment plan in these challenging cases. [ABSTRACT FROM AUTHOR]

Small form-factor sensors are widely used in minimally invasive intravascular diagnostic procedures. Manufacturing complexities associated with miniaturizing current fiber-optic probes, particularly for multi-parameter sensing, severely constrain their adoption outside of niche fields. It is especially challenging to rapidly prototype and iterate upon sensor designs to optimize performance for medical devices. In this work, a novel technique to construct a microscale extrinsic fiber-optic sensor with a confined air cavity and sub-micron geometric resolution is presented. The confined air cavity is enclosed between a 3 μm thick pressure-sensitive distal diaphragm and a proximal temperature-sensitive plano-convex microlens segment unresponsive to changes in external pressure. Simultaneous pressure and temperature measurements are possible through optical interrogation via phase-resolved low-coherence interferometry (LCI). Upon characterization in a simulated intravascular environment, we find these sensors capable of detecting pressure changes down to 0.11 mmHg (in the range of 760 to 1060 mmHg) and temperature changes of 0.036 °C (in the range 34 to 50 °C). By virtue of these sensitivity values suited to intravascular physiological monitoring, and the scope of design flexibility enabled by the precision-fabricated photoresist microstructure, it is envisaged that this technique will enable construction of a wide range of fiber-optic sensors for guiding minimally invasive medical procedures. [ABSTRACT FROM AUTHOR]

Surface structuring provides a broad range of water-repellent materials known for their ability to reflect millimetre-sized raindrops. Dispelling water at the considerably reduced scale of fog or dew, however, constitutes a significant challenge, owing to the comparable size of droplets and structures. Nonetheless, a surface comprising nanocones was recently reported to exhibit strong anti-fogging behaviour, unlike pillars of the same size. To elucidate the origin of these differences, we systematically compare families of nanotexture that transition from pillars to sharp cones. Through environmental electron microscopy and modelling, we show that microdroplets condensing on sharp cones adopt a highly non-adhesive state, even at radii as low as 1.5 µm, contrasting with the behaviour on pillars where pinning results in impedance of droplet ejection. We establish the antifogging abilities to be universal over the range of our cone geometries, which speaks to the unique character of the nanocone geometry to repel dew. Truncated cones are finally shown to provide both pinning and a high degree of hydrophobicity, opposing characteristics that lead to a different, yet efficient, mechanism of dew ejection that relies on multiple coalescences. Spontaneous jumping of condensing droplets holds promise for antifogging, but is generally inhibited for microdroplets. Lecointre et al. show that antifogging ability of cone structures at nanoscales is universal over a large range of cone sizes, shapes, apex angles and even truncation. [ABSTRACT FROM AUTHOR]

We investigate homeotropically aligned fluorophores and Förster resonance energy transfer (FRET) for luminescent solar concentrators using Monte-Carlo ray tracing. The homeotropic alignment strongly improves the trapping efficiency, while FRET circumvents the low absorption at homeotropic alignment by separating the absorption and emission processes. We predict that this design doped with two organic dye molecules can yield a 82.9% optical efficiency improvement compared to a single, arbitrarily oriented dye molecule. We also show that quantum dots are prime candidates for absorption/donor fluorophores due to their wide absorption band. The potentially strong re-absorption and low quantum yield of quantum dots is not a hindrance for this design. [ABSTRACT FROM AUTHOR]

The luminescent solar concentrator (LSC), originally introduced almost four decades ago as a potential alternative/complement to silicon solar cells, has since evolved to a versatile photovoltaic (PV) solution with realistic potential for seamless integration into the urban architectural landscape. Yet, a popular perception of the device still persists: the LSC is mostly seen as just a low‐efficiency solar panel. This review challenges this outdated notion and argues that the LSC is, to the contrary, a powerful and highly adaptive photonic platform with many more capabilities and potential than only generating electricity from sunlight. The field has seen a rapidly expanding application portfolio over the last few years, with LSCs now considered in various sensing applications, "smart" windows, chemical reactors, horticulture, and even in optical communication and real‐time responsive systems. The main goal of this work is to shed light onto this alternative application space and highlight the LSC's unique spectral manipulation, light distribution, and light concentration properties, and as a result, to encourage the participation from a broader range of disciplines into LSC research with the ultimate aim of stimulating the development of novel, LSC inspired technologies. [ABSTRACT FROM AUTHOR]

Vanadium dioxide (VO2) is a promising material in the development of thermal and electrically sensitive devices due to its first order reversible metal‐insulator transition (MIT) at 68 °C. Such high MIT temperature (TC) largely restricts its widespread application which could be enabled if a straightforward tuning mechanism were present. Here this need is addressed through a facile approach that uses the combined effects of temperature induced strain and oxygen vacancies in bulk VO2 colloidal particles. A simple thermal annealing process under varying vacuum is used to achieve phase transformation of metastable VO2(A) into VO2(M2), (M2+M3), (M1) and higher valence V6O13 phases. During this process, distinct multiple phase transitions including increased as well as suppressed TC are observed with respect to the annealing temperature and varied amount of oxygen vacancies respectively. The latent heat of phase transition is also significantly improved upon thermal annealing by increasing the crystallinity of the samples. This work not only offers a facile route for selective phase transformation of VO2 as well as to manipulate the phase transition temperature, but also contributes significantly to the understanding of the role played by oxygen vacancies and temperature induced stress on MIT which is essential for VO2 based applications. [ABSTRACT FROM AUTHOR]

The article explores A 50-year-old man was admitted to the hospital with severe weight loss and pancytopenia (white blood cell count 1.58 × 109 /L, neutrophils 0.66 × 109 /L, hemoglobin 70 g/L, MCV 75.9 fl, platelets 86 × 109 /L). The erythrocyte sedimentation rate was markedly elevated (120 mm/h), and C-reactive protein was slightly abnormal (12 mg/L, ULN: 6 mg/L).

The addition of cations to TiO2 photoelectrodes is routinely accepted as a route to enhance the performance of conventional n‐i‐p solar cells. However, this is typically achieved in multiple steps or by the incorporation of expensive and hydroscopic cationic precursors such as lithium bis(trifluoromethanesulfonyl)imide. In addition, it is often unclear as to whether the incorporation of such cation sources is inducing "doping" or simply transformed into cationic oxides on the surface of the photoelectrodes. In this study, TiO2 nanofibers were produced through a simple electrospinning technique and modified by introducing lithium and lanthanum precursors in one step. Our results show that the addition of both cations caused minimal substitutional or interstitial doping of TiO2. Brunauer‐Emmett‐Teller measurements showed that lanthanum‐treated TiO2 nanofibers had an increase in surface area, which even exceeded that of TiO2 P25 nanoparticles. Finally, treated and untreated TiO2 nanofibers were used in n‐i‐p solar cells. Photovoltaic characteristics revealed that lanthanum treatment was beneficial, whereas lithium treatment was found to be detrimental to the device performance for both dye‐sensitized and perovskite solar cells. The results discuss new fundamental understandings for two of the commonly incorporated cationic dopants in TiO2 photoelectrodes, lithium and lanthanum, and present a significant step forward in advancing the field of materials chemistry for photovoltaics. [ABSTRACT FROM AUTHOR]

Microscopic and mesoscale optical imaging techniques allow for three-dimensional (3-D) imaging of biological tissue across millimeter-scale regions, and imaging phantom models are invaluable for system characterization and clinical training. Phantom models that replicate complex 3-D geometries with both structural and molecular contrast, with resolution and lateral dimensions equivalent to those of imaging techniques (<20 µm), have proven elusive. We present a method for fabricating phantom models using a combination of two-photon polymerization (2PP) to print scaffolds, and microinjection of tailored tissue-mimicking materials to simulate healthy and diseased tissue. We provide a first demonstration of the capabilities of this method with intravascular optical coherence tomography, an imaging technique widely used in clinical practice. We describe the design, fabrication, and validation of three types of phantom models: a first with subresolution wires (5-to 34-µm diameter) arranged circumferentially, a second with a vessel side-branch, and a third containing a lipid inclusion within a vessel. Silicone hybrid materials and lipids, microinjected within a resin framework created with 2PP, served as tissue-mimicking materials that provided realistic optical scattering and absorption. We demonstrate that optical phantom models made with 2PP and microinjected tissue-mimicking materials can simulate complex anatomy and pathology with exquisite detail. [ABSTRACT FROM AUTHOR]

The thermochromic properties of bilayer films consisting of a nanostructured VO2 under-layer and top-layers of ZnO, SnO2 or WO3 are presented. In each case, the VO2 under-layer was deposited by electric field assisted AACVD on a fluorine doped tin oxide coated glass substrate, with the metal oxide top-layer deposited using sol–gel spin coating. The deposited films were analysed and characterised using scanning electron microscopy, X-ray powder diffraction, variable temperature UV/Vis/NIR spectroscopy, X-ray photoelectron spectroscopy, glow discharge photoelectron emission spectroscopy and contact angle measurements. Compared to bare VO2 films, the bilayer films exhibit superior thermochromic properties, with dramatic increases in the visible light transmittance (Tvis), integrated luminous transmittance (Tlum) and solar modulation (ΔTsol). The thermochromic efficiency was also improved in some cases, with a reduction in the hysteresis loop width to ca. 10 °C, and a decrease in the transition temperature (Tc), which was as low as 44 °C and 43 °C for VO2/ZnO and VO2/SnO2 films, respectively. The best balance of thermochromic, thermal protection and aesthetic properties was achieved for ZnO coated films, with the VO2 under-layer deposited at a field strength of 1500 V m−1 under a negative DC bias (Tc = 47 °C, Tlum = 61.6%, Tvis = 68% and ΔTsol = 6%). [ABSTRACT FROM AUTHOR]

The aim of thermochromic window coatings is to reduce the energy consumption in the built environment by passively switching between a high solar transmitting state at low temperatures and low solar transmitting state at high temperatures. Previous studies have highlighted the negative impact of phase transition hysteresis on the performance of reflection based thermochromic films. However in the literature, the best reported results have depended on vanadium dioxide nanoparticle composites and anti-reflective structures that modulate light via changes in absorption rather than reflection. In light of these factors, this work aims to demonstrate theoretically, how the effects of phase transition hysteresis and gradient differ between absorbing and non-absorbing thermochromic films. To quantify and compare the performance of films with different transition characteristics, we define a metric based on the varying net energy flux through the window over the course of a year, including thermal energy re-radiated into the building from the film. Specifically, and importantly for the field, we demonstrate that a pseudo-photochromic effect in absorbing thermochromic films mitigates the detrimental effects of phase transition hysteresis and gradient that have been reported for reflection based thermochromic films. We find that for moderate hysteresis widths of 15 °C, the performance of the non-absorbing case drops to ~60% of its initial value whilst the performance of the absorbing film only drops to ~95%. As a result we find that the absorbing case outperforms the non-absorbing case when hysteresis widths are greater than 8 °C. [ABSTRACT FROM AUTHOR]

Polydimethylsiloxane (PDMS) is widely used in biomedical science and can form composites that have broad applicability. One promising application where PDMS composites offer several advantages is optical ultrasound generation via the photoacoustic effect. Here, methods to create these PDMS composites are reviewed and classified. It is highlighted how the composites can be applied to a range of substrates, from micrometer-scale, temperaturesensitive optical fibers to centimeter-scale curved and planar surfaces. The resulting composites have enabled all-optical ultrasound imaging of biological tissues both ex vivo and in vivo, with high spatial resolution and with clinically relevant contrast. In addition, the first 3D all-optical pulse-echo ultrasound imaging of ex vivo human tissue, using a PDMS-multiwalled carbon nanotube composite and a fiber-optic ultrasound receiver, is presented. Gold nanoparticle-PDMS and crystal violet-PDMS composites with prominent absorption at one wavelength range for pulse-echo ultrasound imaging and transmission at a second wavelength range for photoacoustic imaging are also presented. Using these devices, images of diseased human vascular tissue with both structural and molecular contrast are obtained. With a broader perspective, literature on recent advances in PDMS microfabrication from different fields is highlighted, and methods for incorporating them into new generations of optical ultrasound generators are suggested. [ABSTRACT FROM AUTHOR]

Highly sensitive broadband ultrasound detectors are needed to expand the capabilities of biomedical ultrasound, photoacoustic imaging and industrial ultrasonic non-destructive testing techniques. Here, a generic optical ultrasound sensing concept based on a novel plano-concave polymer microresonator is described. This achieves strong optical confinement (Q-factors > 105) resulting in very high sensitivity with excellent broadband acoustic frequency response and wide directivity. The concept is highly scalable in terms of bandwidth and sensitivity. To illustrate this, a family of microresonator sensors with broadband acoustic responses up to 40 MHz and noise-equivalent pressures as low as 1.6 mPa per √Hz have been fabricated and comprehensively characterized in terms of their acoustic performance. In addition, their practical application to high-resolution photoacoustic and ultrasound imaging is demonstrated. The favourable acoustic performance and design flexibility of the technology offers new opportunities to advance biomedical and industrial ultrasound-based techniques. An optical-based scheme for ultrasound sensing provides very high sensitivity with excellent broadband acoustic frequency response and wide directivity. [ABSTRACT FROM AUTHOR]

All-optical ultrasound transducers are promising for imaging applications in minimally invasive surgery. In these devices, ultrasound is transmitted and received through laser modulation, and they can be readily miniaturized using optical fibers for light delivery. Here, we report optical ultrasound transmitters fabricated by electrospinning an absorbing polymer composite directly onto the end-face of optical fibers. The composite coating consisting of an aqueous dispersion of multi-walled carbon nanotubes (MWCNTs) in polyvinyl alcohol was directly electrospun onto the cleaved surface of a multimode optical fiber and subsequently dip-coated with polydimethylsiloxane (PDMS). This formed a uniform nanofibrous absorbing mesh over the optical fiber end-face wherein the constituent MWCNTs were aligned preferentially along individual nanofibers. Infiltration of the PDMS through this nanofibrous mesh onto the underlying substrate was observed and the resulting composites exhibited high optical absorption (>97%). Thickness control from 2.3 μm to 41.4 μm was obtained by varying the electrospinning time. Under laser excitation with 11 μJ pulse energy, ultrasound pressures of 1.59MPa were achieved at 1.5mm from the coatings. On comparing the electrospun ultrasound transmitters with a dip-coated reference fabricated using the same constituent materials and possessing identical optical absorption, a five-fold increase in the generated pressure and wider bandwidth was observed. The electrospun transmitters exhibited high optical absorption, good elastomer infiltration, and ultrasound generation capability in the range of pressures used for clinical pulse-echo imaging. All-optical ultrasound probes with such transmitters fabricated by electrospinning could be well-suited for incorporation into catheters and needles for diagnostics and therapeutic applications. [ABSTRACT FROM AUTHOR]

Polymer-carbon nanotube composite coatings have properties that are desirable for a wide range of applications. However, fabrication of these coatings onto submillimeter structures with the efficient use of nanotubes has been challenging. Polydimethylsiloxane (PDMS)-carbon nanotube composite coatings are of particular interest for optical ultrasound transmission, which shows promise for biomedical imaging and therapeutic applications. In this study, methods for fabricating composite coatings comprising PDMS and multiwalled carbon nanotubes (MWCNTs) with submicrometer thickness are developed and used to coat the distal ends of optical fibers. These methods include creating a MWCNT organogel using two solvents, dip coating of this organogel, and subsequent overcoating with PDMS. These coated fibers are used as all-optical ultrasound transmitters that achieve high ultrasound pressures (up to 21.5 MPa peak-to-peak) and broad frequency bandwidths (up to 39.8 MHz). Their clinical potential is demonstrated with all-optical pulse-echo ultrasound imaging of an aorta. The fabrication methods in this paper allow for the creation of thin, uniform carbon nanotube composites on miniature or temperature-sensitive surfaces, to enable a wide range of advanced sensing capabilities. [ABSTRACT FROM AUTHOR]

Heavy inorganic scintillator based detectors are used in various applications. You can find them in high energy physics as well as in nuclear medical imaging systems but also in homeland security radiation monitoring devices. In all these different detectors, light is produced in the scintillator and has to be transported towards a photodetector. The standard optical coupling of such a detector suffers from an inefficient light extraction towards the photodetector due to the high index of refraction of the scintillator and the accompanying total internal reflections. With the means of photonic nanostructuring of the different surfaces of the scintillator, the light transport can be optimized, which has a direct impact on the timing and light yield performance of the detector. Previous work from our group has already shown that photonic crystals (PhCs) can be used as diffraction gratings to improve the light coupling between a photodetector and a scintillator. Moreover, nanoscale surface structuring techniques could also be extended to the sidewalls, the wrapping, or the detector itself, which would open up a number of new possibilities for optimization of the light transport of scintillation based detectors. To show that PhCs can also be produced on a large industrial scale, we started to investigate different methods for cheap and large area PhC structuring. In this work, the current results on our efforts on PhC scintillator production will be described. The different projects include nanoimprint technologies, interference lithography and colloidal lithography. To conclude, we will summarize the different efforts of our group and collaborators and show up-to-date results of PhC improved scintillators. [ABSTRACT FROM AUTHOR]

“Photonic Crystals (PhC)” have been used in a variety of fields as a structure for improving the light extraction efficiency from materials with high index of refraction. In previous work we already showed the light extraction improvement of several PhC covered LYSO crystals in computer simulations and practical measurements. In this work, new samples are made using different materials and techniques which allows further efficiency improvements. For rapid prototyping of PhC patterns on scintillators we tested a new method using “Focused Ion Beam (FIB)” patterning. The FIB machine is a device similar to a “Scanning Electron Microscope (SEM)”, but it uses ions (mainly gallium) instead of electrons for the imaging of the samples’ surface. The additional feature of FIB devices is the option of surface patterning in nano-scale which was exploited for our samples. Three samples using FIB patterning have been produced. One of them is a direct patterning of the extraction face of a 0.8\times 0.8\times 10~\mm^3 LYSO crystal. The second and third were TiO_2 coated LYSO crystal with a 1.4\times 1.4~\mm^2 out coupling face partly covered with high-quality photonic crystals. TiO_2 has high refractive index (around 2.1 - 2.4)–which shows the best results in our light extraction simulations. In this paper, SEM images of the samples will be presented together with measurements of excited crystals which show unrivalled performance for such scintillator samples. [ABSTRACT FROM AUTHOR]

In this paper, we experimentally demonstrate a multiband carrierless amplitude and phase modulation format for the first time in VLC. We split a conventional carrierless amplitude and phase modulated signal into \boldsymbolm subcarriers in order to protect from the attenuation experienced at high frequencies in low-pass VLC systems. We investigate the relationship between throughput/spectral efficiency and \boldsymbolm, where \boldsymbolm=\10,8,6,4,2,1\ subcarriers over a fixed total signal bandwidth of 6.5 MHz. We show that transmission speeds (spectral efficiencies) of 31.53 (4.85), 30.88 (4.75), 25.40 (3.90), 23.65 (3.60), 15.78 (2.40), and 9.04 (1.40) Mb/s (b/s/Hz) can be achieved for the listed values of \boldsymbolm, respectively. [ABSTRACT FROM PUBLISHER]

We present recent progress on visible light communication systems using polymer light-emitting diodes as the transmitters and a commercial silicon photodetector as the receiver. In this paper, we use transmitters at red, green, and blue wavelengths to investigate the maximum on-off keying link performance of each device type as the first steps toward a wavelength-division multiplexed link. We show that a total transmission speed of 13 Mb/s is achievable when considering the raw bandwidth of each of the RGB PLEDs. Such a rate represents a 30% gain over previously demonstrated systems. Further capacity improvement can be achieved using high performance artificial neural network equalizer offering a realistic prospect for transmission speeds up to 54.9 Mb/s. [ABSTRACT FROM PUBLISHER]

Visible light communications is a technology with enormous potential for a wide range of applications within next generation transmission and broadcasting technologies. VLC offers simultaneous illumination and data communications by intensity modulating the optical power emitted by LEDs operating in the visible range of the electromagnetic spectrum (~370?780 nm). The major challenge in VLC systems to date has been in improving transmission speeds, considering the low bandwidths available with commercial LED devices. Thus, to improve the spectral usage, the research community has increasingly turned to advanced modulation formats such as orthogonal frequency-division multiplexing. In this article we introduce a new modulation scheme into the VLC domain; multiband carrier-less amplitude and phase modulation (m-CAP) and describe in detail its performance within the context of bandlimited systems. [ABSTRACT FROM PUBLISHER]

This letter experimentally demonstrates a visible light communication system using a 350-kHz polymer light-emitting diode operating at a total bit rate of 19 Mb/s with a bit error rate (BER) of 10-6 and 20 Mb/s at the forward error correction limit for the first time. This represents a remarkable net data rate gain of ~55 times. The modulation format adopted is ON-OFF keying in conjunction with an artificial neural network classifier implemented as an equalizer. The number of neurons used in the experiment is varied from the set N = 5, 10, 20, 30, 40 with 40 neurons offering the best performance at 19 Mb/s and the BER of 10-6. [ABSTRACT FROM PUBLISHER]

This letter presents new experimental results on a 1-Mb/s organic visible light communications system. These results are the first demonstration of a fully organic free space optical communications system. Due to low charge transport characteristics, organic devices are typically highly band limited in the hundreds of kilohertz region (up to 135 kHz in this letter). Therefore, an artificial neural network (ANN) equalizer is required to undo the effects of intersymbol interference. Without the ANN, the maximum link performance corresponds to a data rate of 350 kb/s; however, with the ANN, a transmission speed of 1.15 Mb/s could be supported. [ABSTRACT FROM PUBLISHER]

The uncertainty in time of particle detection within a scintillator detector, characterised by the coinci- dence time resolution (CTR), is explored with respect to the interaction position within the scintillator crystal itself. Electronic collimation between two scintillator detectors is utilised to determine the CTR with depth of interaction (DOI) for different materials, geometries and wrappings. Significantly, no rela- tionship between the CTR and DOI is observed within experimental error. Confinement of the interaction position is seen to degrade the CTR in long scintillator crystals by 10%. [ABSTRACT FROM AUTHOR]

In this paper, we experimentally demonstrate for the first time an on off keying modulated visible light communications system achieving 170 Mb/s using an artificial neural network (ANN) based equalizer. Adaptive decision feedback (DF) and linear equalizers are also implemented and the system performances are measured using both real time (TI TMS320C6713 digital signal processing board) and offline (MATLAB) implementation of the equalizers. The performance of each equalizer is analyzed in this paper using a low bandwidth (4.5 MHz) light emitting diode (LED) as the transmitter and a large bandwidth (150 MHz) PIN photodetector as the receiver. The achievable data rates using the white spectrum are 170, 90, 40 and 20 Mb/s for ANN, DF, linear and unequalized topologies, respectively. Using a blue filter to isolate the fast blue component of the LED (at the cost of the power contribution of the yellowish wavelengths) is a popular method of improving the data rate. We further demonstrate that it is possible to sustain higher data rates from the white light with ANN equalization than the blue component due to the high signal-to-noise ratio that is obtained from retaining the yellowish wavelengths. Using the blue component we could achieve data rates of 150, 130, 90 and 70 Mb/s for the same equalizers, respectively. [ABSTRACT FROM PUBLISHER]

Optical ultrasound transducers were created by coating optical fibres with a composite of carbon nanotubes (CNTs) and polydimethylsiloxane (PDMS). Dissolution of CNTs in PDMS to create the composite was facilitated by functionalisation with oleylamine. Composite surfaces were applied to optical fibres using dip coating. Under pulsed laser excitation, ultrasound pressures of 3.6 MPa and 4.5 MPa at the coated end faces were achieved with optical fibre core diameters of 105 and 200 μm, respectively. The results indicate that CNT-PDMS composite coatings on optical fibres could be viable alternatives to electrical ultrasound transducers in miniature ultrasound imaging probes. [ABSTRACT FROM AUTHOR]

We investigate the radiation hardness of Reflective Electroabsorption Modulators (REAMs) for fluence levels up to 14 \times 10^15 24 GeV p/cm^2 to explore the possibility of utilising REAMs for data readout at the High-Luminosity Large Hadron Collider (HL-LHC). The high fluence levels used in the experiment and the online spectral measurements carried out provide significant insight into the radiation damage mechanism. The radiation limits of an architecture based on REAMs are established and compared to LHC and HL-LHC fluence levels. [ABSTRACT FROM PUBLISHER]

The protocol data rate governing data storage devices will increase to over 12 Gb/s by 2013 thereby imposing unmanageable cost and performance burdens on future digital data storage systems. The resulting performance bottleneck can be substantially reduced by conveying high-speed data optically instead of electronically. A novel active pluggable 82.5 Gb/s aggregate bit rate optical connector technology, the design and fabrication of a compact electro-optical printed circuit board to meet exacting specifications, and a method for low cost, high precision, passive optical assembly are presented. A demonstration platform was constructed to assess the viability of embedded electro-optical midplane technology in such systems including the first ever demonstration of a pluggable active optical waveguide printed circuit board connector. High-speed optical data transfer at 10.3125 Gb/s was demonstrated through a complex polymer waveguide interconnect layer embedded into a 262 mm\,\times\,240 mm\,\times\,4.3 mm electro-optical midplane. Bit error rates of less than 10^-12 and optical losses as low as 6 dB were demonstrated through nine multimode polymer wave guides with an aggregate data bandwidth of 92.8125 Gb/s. [ABSTRACT FROM PUBLISHER]

The present paper discusses recent advances on a Passive Optical Network inspired Timing-Trigger and Control scheme for the future upgrade of the TTC system installed in the LHC experiments' and more specifically the currently known as TTCex to TTCrx link. The timing PON is implemented with commercially available FPGAs and 1-Gigabit Ethernet PON transceivers and provides a fixed latency gigabit downlink that can carry level-1 trigger accept decisions and commands as well as an upstream link for feedback from the front-end electronics. [ABSTRACT FROM PUBLISHER]

The first, to our knowledge, passive, precision, self- alignment technique for direct coupling of vertical cavity surface emitting laser (VCSEL) and photodiode (PD) arrays to an array of polymer buried channel waveguides on a rigid printed circuit board (PCB) is reported. It gives insertion losses as good as the best achieved previously, to within experimental measurement accuracy, but without the need for costly active alignment nor waveguide facet polishing and so is a major step towards a commercially realizable low cost connector. Such an optical connector with four duplex channels each operating at 10 Gb/s (80 Gb/s aggregate) was designed, constructed, and its alignment precision assessed. The alignment technique is applicable to polymer waveguide interconnections on both rigid and flexible multilayer printed circuit boards (PCBs). The dependence of optical coupling loss on misalignments in x, y and z of the VCSEL and PD arrays allows the precision of alignment to be assessed and its reproducibility on multiple mating cycles of the connector is reported. The first recorded measurements of crosstalk between waveguides when the connector is misaligned are reported. Lateral misalignments of the connector to within its tolerance are shown to have no effect on the signal to crosstalk ratio (SCR), to within experimental measurement accuracy. The insertion loss repeatability is similar to that of single mode fiber mechanically transferable (MT) connectors. [ABSTRACT FROM AUTHOR]