scholarly journals The reduction of the thermal quenching effect in laser-excited phosphor converters using highly thermally conductive hBN particles

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Akvilė Zabiliūtė-Karaliūnė ◽  
Justina Aglinskaitė ◽  
Prancis̆kus Vitta
Keyword(s):  
Hexagonal Boron Nitride ◽  
Imaging Techniques ◽  
Thermal Quenching ◽  
Optical Power ◽  
Excitation Power ◽  
Excitation Power Density ◽  
Quenching Effect ◽  
Wide Range ◽  
Thermally Conductive ◽  
Phosphor Thermometry

AbstractPhosphor converters for solid state lighting applications experience a strong thermal stress under high-excitation power densities. The recent interest in laser diode based lighting has made this issue even more severe. This research presents an effective approach to reduce the thermal quenching effect and damage of laser-excited phosphor-silicone converters using thermally conductive hexagonal boron nitride (hBN) particles. Herein, the samples are analyzed by employing phosphor thermometry based on the photoluminescence decay time, and thermo-imaging techniques. The study shows that hBN particle incorporation increases the thermal conductivity of a phosphor-silicone mixture up to 5 times. It turns out, that the addition of hBN to the Eu$$^{2+}$$ 2 + doped chalcogenide-silicone converters can increase the top-limit excitation power density from 60 to 180 W cm$$^{-2}$$ - 2 , thus reaching a 2.5 times higher output. Moreover, it is shown that the presence of hBN in Ce$$^{3+}$$ 3 + activated garnet phosphor converters, may increase the output power by up to 1.8 times and that such converters can withstand 218 W cm$$^{-2}$$ - 2 excitation. Besides, hBN particles are also found to enhance the stability of the converters chromaticity and luminous efficacy of radiation. This means that the addition of hBN particles into silicone-based phosphor converter media is applicable in a wide range of different areas, in particular, the ones requiring a high optical power output density.

scholarly journals Threshold increase and lasing inhibition due to hexagonal-pyramid-shaped hillocks in AlGaN-based DUV laser diodes on single-crystal AlN substrate

2021 ◽  
Author(s):  
Maki Kushimoto ◽  
Ziyi Zhang ◽  
Yoshio HONDA ◽  
Leo John Schowalter ◽  
Chiaki Sasaoka ◽  
...  
Keyword(s):  
Imaging Techniques ◽  
Laser Diodes ◽  
Optical Excitation ◽  
Threshold Current ◽  
Excitation Power ◽  
Threshold Current Density ◽  
Excitation Power Density ◽  
Threshold Excitation ◽  
The Difference ◽  
Hexagonal Pyramid

Abstract The presence of hexagonal-pyramid-shaped hillocks (HPHs) in AlGaN epitaxial films affects device character- istics; this effect is significant in DUV laser diodes (LDs) on AlN substrates, where the presence of HPHs under the p-electrode increases the threshold current density and inhibits the lasing. In this study, we investigated the difference between the lasing characteristics of LDs with and without HPHs. It was found that in the presence of HPHs, the threshold excitation power density increased and the slope efficiency decreased by optical excitation. To investigate the cause of these phenomena, we performed structural, optical, and electrical analyses of the HPHs. Various imaging techniques were used to directly capture the characteristics of the HPHs. As a result, we concluded that HPHs cause the degradation of LD characteristics due to a combination of structural, optical, and electrical factors.

Molecular Imaging of Red Blood Cells by Raman Spectroscopy

2011 ◽  
Vol 64 (5) ◽  
pp. 593 ◽  
Author(s):  
Bayden R. Wood ◽  
Paul R. Stoddart ◽  
Donald McNaughton
Keyword(s):  
Biological Sciences ◽  
Raman Spectroscopy ◽  
Red Blood Cells ◽  
Blood Cells ◽  
Early Stage ◽  
Imaging Techniques ◽  
Excitation Power ◽  
Diagnostic Potential ◽  
Wide Range ◽  
Technical Advances

Raman spectroscopy allows visualization of 2D and 3D chemical distributions at high spatial resolution in a wide range of samples. It is insensitive to water, which makes it particularly attractive for applications in the biological sciences. At the same time, technical advances have allowed the laser excitation power to be reduced on thermally sensitive samples, without sacrificing acquisition times. This review highlights the analytical and diagnostic potential of Raman imaging techniques by reference to recent studies of red blood cells. In the case of red blood cells infected with low-pigmented forms of the malaria parasite, molecular images reveal sub-micron-inclusions of haemozoin, which suggests that the technique has potential for early-stage diagnosis of the disease.

The sensitization of laser-induced heat of Er3+ doped Y2O3 nanocrystals by codoped with Mn2+

2015 ◽  
Vol 29 (22) ◽  
pp. 1550158
Author(s):  
Yunfeng Bai ◽  
Minjie Luan ◽  
Linjun Li ◽  
Zhelong He ◽  
Dongyu Li
Keyword(s):  
Power Density ◽  
Thermal Emission ◽  
Energy Levels ◽  
Excitation Power ◽  
Threshold Power ◽  
Excitation Power Density ◽  
Ir Laser ◽  
Order Of Magnitude ◽  
Low Threshold ◽  
Density Threshold

Low threshold power density cw laser-induced heat has been observed in [Formula: see text] and [Formula: see text] codoped [Formula: see text] nanocrystals under excitation by a 980 nm IR laser. Codoped [Formula: see text] remarkably reduces the power density threshold of laser-induced heat compared with [Formula: see text] doped [Formula: see text] nanocrystals. When the excitation power density exceed [Formula: see text], [Formula: see text] codoped [Formula: see text] nanocrystals emit strong blackbody radiation. The thermal emission of [Formula: see text] should originate from the multiphonon relaxation between neighboring energy levels. One additional UC-PL enhancement is observed. The UC-PL intensity can be enhanced by an order of magnitude through high temperature calcination caused by light into heat.

scholarly journals MoS2/h-BN/Graphene Heterostructure and Plasmonic Effect for Self-Powering Photodetector: A Review

Materials ◽  
2021 ◽  
Vol 14 (7) ◽  
pp. 1672
Author(s):  
Umahwathy Sundararaju ◽  
Muhammad Aniq Shazni Mohammad Haniff ◽  
Pin Jern Ker ◽  
P. Susthitha Menon
Keyword(s):  
Flexible Electronics ◽  
Hexagonal Boron Nitride ◽  
2D Materials ◽  
Optical Power ◽  
Active Regions ◽  
Green Technology ◽  
Plasmonic Effect ◽  
Zero Bias ◽  
Electrical Signals ◽  
Self Powered

A photodetector converts optical signals to detectable electrical signals. Lately, self-powered photodetectors have been widely studied because of their advantages in device miniaturization and low power consumption, which make them preferable in various applications, especially those related to green technology and flexible electronics. Since self-powered photodetectors do not have an external power supply at zero bias, it is important to ensure that the built-in potential in the device produces a sufficiently thick depletion region that efficiently sweeps the carriers across the junction, resulting in detectable electrical signals even at very low-optical power signals. Therefore, two-dimensional (2D) materials are explored as an alternative to silicon-based active regions in the photodetector. In addition, plasmonic effects coupled with self-powered photodetectors will further enhance light absorption and scattering, which contribute to the improvement of the device’s photocurrent generation. Hence, this review focuses on the employment of 2D materials such as graphene and molybdenum disulfide (MoS2) with the insertion of hexagonal boron nitride (h-BN) and plasmonic nanoparticles. All these approaches have shown performance improvement of photodetectors for self-powering applications. A comprehensive analysis encompassing 2D material characterization, theoretical and numerical modelling, device physics, fabrication and characterization of photodetectors with graphene/MoS2 and graphene/h-BN/MoS2 heterostructures with plasmonic effect is presented with potential leads to new research opportunities.

scholarly journals Potential predictors of severe cardiovascular involvement in Marfan syndrome: the emphasized role of genotype–phenotype correlations in improving risk stratification—a literature review

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Roland Stengl ◽  
Bence Ágg ◽  
Miklós Pólos ◽  
Gábor Mátyás ◽  
Gábor Szabó ◽  
...  
Keyword(s):  
Risk Stratification ◽  
Marfan Syndrome ◽  
Current Knowledge ◽  
Imaging Techniques ◽  
Connective Tissue Disorder ◽  
Main Body ◽  
Wide Range ◽  
Stratification System ◽  
Genetically Determined ◽  
Aortic Dissections

Abstract Background Marfan syndrome (MFS) is a genetically determined systemic connective tissue disorder, caused by a mutation in the FBN1 gene. In MFS mainly the cardiovascular, musculoskeletal and ocular systems are affected. The most dangerous manifestation of MFS is aortic dissection, which needs to be prevented by a prophylactic aortic root replacement. Main body The indication criteria for the prophylactic procedure is currently based on aortic diameter, however aortic dissections below the threshold defined in the guidelines have been reported, highlighting the need for a more accurate risk stratification system to predict the occurrence of aortic complications. The aim of this review is to present the current knowledge on the possible predictors of severe cardiovascular manifestations in MFS patients, demonstrating the wide range of molecular and radiological differences between people with MFS and healthy individuals, and more importantly between MFS patients with and without advanced aortic manifestations. These differences originating from the underlying common molecular pathological processes can be assessed by laboratory (e.g. genetic testing) and imaging techniques to serve as biomarkers of severe aortic involvement. In this review we paid special attention to the rapidly expanding field of genotype–phenotype correlations for aortic features as by collecting and presenting the ever growing number of correlations, future perspectives for risk stratification can be outlined. Conclusions Data on promising biomarkers of severe aortic complications of MFS have been accumulating steadily. However, more unifying studies are required to further evaluate the applicability of the discussed predictors with the aim of improving the risk stratification and therefore the life expectancy and quality of life of MFS patients.

scholarly journals The Optical Properties of InGaN/GaN Nanorods Fabricated on (-201) β-Ga2O3 Substrate for Vertical Light Emitting Diodes

Photonics ◽  
2021 ◽  
Vol 8 (2) ◽  
pp. 42
Author(s):  
Jie Zhao ◽  
Weijiang Li ◽  
Lulu Wang ◽  
Xuecheng Wei ◽  
Junxi Wang ◽  
...  
Keyword(s):  
Stark Effect ◽  
Light Emitting Diodes ◽  
Light Emitting Diode ◽  
Strain Relaxation ◽  
Blue Shift ◽  
Peak Position ◽  
Excitation Power ◽  
Light Extraction Efficiency ◽  
Excitation Power Density ◽  
Light Emitting

We fabricated InGaN/GaN nanorod light emitting diode (LED) on (-201) β-Ga2O3 substrate via the SiO2 nanosphere lithography and dry-etching techniques. The InGaN/GaN nanorod LED grown on β-Ga2O3 can effectively suppress quantum confined Stark effect (QCSE) compared to planar LED on account of the strain relaxation. With the enhancement of excitation power density, the photoluminescence (PL) peak shows a large blue-shift for the planar LED, while for the nanorod LED, the peak position shift is small. Furthermore, the simulations also show that the light extraction efficiency (LEE) of the nanorod LED is approximately seven times as high as that of the planar LED. Obviously, the InGaN/GaN/β-Ga2O3 nanorod LED is conducive to improving the optical performance relative to planar LED, and the present work may lay the groundwork for future development of the GaN-based vertical light emitting diodes (VLEDs) on β-Ga2O3 substrate.

scholarly journals A Structurally Variable Hinged Tetrahedron Framework from DNA Origami

2011 ◽  
Vol 2011 ◽  
pp. 1-9 ◽  
Author(s):  
David M. Smith ◽  
Verena Schüller ◽  
Carsten Forthmann ◽  
Robert Schreiber ◽  
Philip Tinnefeld ◽  
...  
Keyword(s):  
Self Assembly ◽  
Gel Electrophoresis ◽  
Imaging Techniques ◽  
Building Blocks ◽  
Dna Origami ◽  
Microscopy Technique ◽  
Wire Frame ◽  
Wide Range ◽  
Potential Applications ◽  
Linker Molecules

Nanometer-sized polyhedral wire-frame objects hold a wide range of potential applications both as structural scaffolds as well as a basis for synthetic nanocontainers. The utilization of DNA as basic building blocks for such structures allows the exploitation of bottom-up self-assembly in order to achieve molecular programmability through the pairing of complementary bases. In this work, we report on a hollow but rigid tetrahedron framework of 75 nm strut length constructed with the DNA origami method. Flexible hinges at each of their four joints provide a means for structural variability of the object. Through the opening of gaps along the struts, four variants can be created as confirmed by both gel electrophoresis and direct imaging techniques. The intrinsic site addressability provided by this technique allows the unique targeted attachment of dye and/or linker molecules at any point on the structure's surface, which we prove through the superresolution fluorescence microscopy technique DNA PAINT.

scholarly journals Fiber Optical Hydrogen Sensor Based on WO3-Pd2Pt-Pt Nanocomposite Films

Nanomaterials ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 128
Author(s):  
Jixiang Dai ◽  
Yi Li ◽  
Hongbo Ruan ◽  
Zhuang Ye ◽  
Nianyao Chai ◽  
...  
Keyword(s):  
Optical Power ◽  
Single Mode ◽  
Hydrogen Sensor ◽  
Single Mode Fiber ◽  
Nanocomposite Films ◽  
Electric Signal ◽  
Hydrogen Sensing ◽  
Air Atmosphere ◽  
Sensing Material ◽  
Wide Range

In this paper, WO3-Pd2Pt-Pt nanocomposite films were deposited on a single mode fiber as the hydrogen sensing material, which changes its reflectivity under different hydrogen concentration. The reflectivity variation was probed and converted to an electric signal by a pair of balanced InGaAs photoelectric detectors. In addition, the performance of the WO3-Pd2Pt-Pt composite film was investigated under different optical powers, and the irrigating power was optimized at 5 mW. With the irrigation of this optical power, the hydrogen sensitive film exhibits quick response toward 100 ppm hydrogen in air atmosphere at a room temperature of 25 °C. The experimental results demonstrate a high resolution at 5 parts per million (ppm) within a wide range from 100 to 5000 ppm in air. This simple and compact sensing system can detect hydrogen concentrations far below the explosion limit and provide early alert for hydrogen leakage, showing great potential in hydrogen-related applications.

Updates and Advances: Pediatric Musculoskeletal Infection Imaging Made Easier for Radiologists and Clinicians

2021 ◽  
Vol 25 (01) ◽  
pp. 167-175
Author(s):  
Michael S. Furman ◽  
Ricardo Restrepo ◽  
Supika Kritsaneepaiboon ◽  
Bernard F. Laya ◽  
Domen Plut ◽  
...  
Keyword(s):  
Clinical Practice ◽  
Imaging Techniques ◽  
Daily Clinical Practice ◽  
Infants And Children ◽  
Imaging Evaluation ◽  
Musculoskeletal Infection ◽  
Wide Range ◽  
Life Threatening ◽  
Optimal Patient Management

AbstractInfants and children often present with a wide range of musculoskeletal (MSK) infections in daily clinical practice. This can vary from relatively benign superficial infections such as cellulitis to destructive osseous and articular infections and life-threatening deep soft tissue processes such as necrotizing fasciitis. Imaging evaluation plays an essential role for initial detection and follow-up evaluation of pediatric MSK infections. Therefore, a clear and up-to-date knowledge of imaging manifestations in MSK infections in infants and children is imperative for timely and accurate diagnosis that, in turn, can result in optimal patient management. This article reviews an up-to-date practical imaging techniques, the differences between pediatric and adult MSK infections, the spectrum of pediatric MSK infections, and mimics of pediatric MSK infections encountered in daily clinical practice by radiologists and clinicians.

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