High-power Sources Research Articles

Miniaturized Time-Domain Antenna With Improved Low-Frequency Radiation Performance

A miniaturized end-fire antenna with improved low-frequency radiation performance (RP) is proposed for time- domain applications. Through a novel resistive loading (RL) method, the proposed time-domain antenna (TDA) has a compact size of 0.176 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</sub> ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</i> ) × 0.156 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</sub> ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">W</i> ), and improved low-frequency RP. Note that, this improvement does not mean the improvement of radiation efficiency, but means the enhancement of the radiation in forward and the reduction of the radiation in backward. Furthermore, the size of the proposed TDA is reduced by 78% as compared with the traditional antipodal Vivaldi antenna (AVA). In order to provide a certain reference for the design of end-fire TDAs, the mechanism of the novel RL technique is explored according to the design. Measured results show that the bandwidth of the proposed TDA is 0.168 ∼ 3 GHz (179%). Due to the compact size and good time-domain performance, the proposed TDA can be a good candidate for time-domain applications such as ground penetrating radar (GPR), Through-Wall Radar (TWR) and high-power pulsed source (HPS). Meanwhile, the novel RL technique can be a prior solution for the miniaturization and low-frequency RP improvement for end-fire TDAs.

High-Power Source of Narrow-Band Radiation Based on Integrated External-Cavity Laser Diodes

High-Power Source of Narrow-Band Radiation Based on Integrated External-Cavity Laser Diodes

Power over fiber using a large core fiber and laser operating at 976 nm with 10 W power

We report on the properties of a powering transmission link based on a High-Power Laser Source operating at 976 nm and large-core 105 μm multimode optical fiber at a distance of 200 m. Six types of Photovoltaic Power Converters were used to convert optical power to electric power and the results are presented and discussed, as well as the properties of transport of the energy through the multimode fiber ending with an optical 1x2Y splitter.

Numerical Simulation of High-Power Optical Amplifiers at 2.3 µm Based on a Special Multicore Fiber

The development of high-power laser sources at 2.3 µm is highly demanded for remote sensing and other applications. However, this wavelength is poorly covered by present-day lasers. To obtain 100 W class high-power radiation at 2.3 μm, we propose to use simultaneously cascade laser amplification at 2 and 2.3 µm with a commercially available diode pump at 793 nm and stimulated Raman scattering between the amplified signal waves in a special zinc–tellurite multicore fiber with ten trivalent-thulium-ion-doped cores arranged in a ring. We demonstrate numerically that the use of an out-of-phase supermode (with spatial phases differing by π in neighboring cores) can provide up to 50% efficiency conversion from the 793 nm pump to the 2.3 µm wave.

High-power two-color plasma-based THz generation driven by a Tm-doped fiber laser.

We report on the efficient generation of broadband THz radiation based on a two-color gas-plasma scheme. Broadband THz pulses covering the whole THz spectral region, from 0.1-35 THz, are generated. This is enabled by a high-power, ultra-fast, thulium-doped, fiber chirped pulse amplification (Tm:FCPA) system and a subsequent nonlinear pulse compression stage that uses a gas-filled capillary. The driving source delivers 40 fs pulses at a central wavelength of 1.9 μm with 1.2 mJ pulse energy and 101 kHz repetition rate. Owing to the long driving wavelength and the use of a gas-jet in the THz generation focus, the highest reported conversion efficiency for high-power THz sources (>20 mW) of 0.32% has been achieved. The high efficiency and average power of 380 mW of the broadband THz radiation make this an ideal source for nonlinear, tabletop THz science.

Investigation the performance of the recompression Brayton cycle with different N2O-based binary mixtures for a nuclear power spacecraft

The development of space power supply and space propulsion technology based on solar and chemical energy has approached the limit state. Large-scale space missions such as solar system marginal exploration, deep space orbit transfer and manned deep space exploration have put forward higher requirements for highly reliable, sustainable and high-power power sources. With the potential development of compact components, the S-CO2 recompression Brayton cycle has attracted much attention to improve the key technologies of nuclear power spacecraft and reduce the system mass and research and development cost. To weaken the constraint of the critical point of the supercritical working medium on the minimum cycle conditions, the additional gas mixed with pure N2O as the working medium can change the critical point properties to improve the cycle efficiency. At this present study stage, there is no specific standard for selecting the appropriate binary mixture components to improve the cycle efficiency. This study analyzed the physical properties of N2O-based binary mixtures and adopted them as a criterion to judge whether the N2O-based binary mixture can improve the cycle efficiency. Finally, according to the analysis results obtained and specific system environment requirements, several factors have been identified the selection criteria for N2O-based binary mixtures. The conclusion of this work is that the working medium with a more significant entropy difference, a higher specific heat capacity for the compressor close to the minimum cycle temperature in a specific temperature range and a lower maximum enthalpy of the N2O-based binary mixtures can obtain a higher cycle efficiency. Moreover, the substances reduce the critical temperature under that of N2O; in this scenario, the thermal performance is improved compared with pure S-N2O.

Identification of high-power density source requirement for electric vehicle during on-road conditions

This paper describes various setups for testing electric vehicle (EV) on-road operating conditions. The significance of a high-power density energy source during EV acceleration and deceleration is highlighted in this work. The drive motor (DM) draws a large current during acceleration, the magnitude of which is determined by the acceleration time and vehicle parameters. Also, the source must capture all of the regenerative power from the DM during deceleration. The battery life will be reduced if it is used as an energy source for acceleration. Furthermore, due to its low power–density, the battery cannot quickly store regenerative power. To meet the aforementioned requirements, a high power–density source, such as an ultracapacitor (UC), is required. The simulation results as well as hardware results are shown for EV emulation systems.

A High-Power Source of Ultrawideband Radiation of Subnanosecond Duration with Controllable Characteristics

A High-Power Source of Ultrawideband Radiation of Subnanosecond Duration with Controllable Characteristics

Distributed focusing reduces mirror error sensitivity on x-ray beamlines.

The appearance of very low emittance, high-power synchrotron sources has resulted in ever longer beamlines, often requiring a very weak curvature on the mirrors that transport the beam to the experiment, where the radius of curvature is on the order of kilometers. Manufacturing weakly curved, low figure error grazing incidence mirrors is difficult as the mirrors must be manufactured to an accuracy comparable to the wavelength of the transmitted light. Often the delivered mirrors have figure errors at various length scales (general shape, slope errors, roughness), which compromise image quality. An error in general shape, like the radii of a toroidal mirror, results in long-sighted or short-sighted imaging that is not so simply corrected by changing the distances and incidence angles as the mirror controls the beam focus in both vertical and horizontal directions; for a toroidal mirror, the tangential and sagittal radii need to match correctly for the desired focusing effect. Adaptive downstream optics can compensate for this. In this paper, an alternative method to reduce the sensitivity to a large radius error outside the specified tolerance range in the first mirror of a plane grating monochromator beamline at MAX IV is presented. It is found that distributed focusing by two passive, fixed radius mirrors reduces greatly the sensitivity to the radius errors in both mirrors. The radius tolerance of a mirror initially found to be unacceptable for single stage focusing is easily accommodated on both mirrors in distributed focusing, without compromising the imaging capability.

Public exposure to artificial optical radiation in the aesthetics and the entertainment sector in Greece. Risk management actions.

Safety issues are raised from the use of low- and high-power optical radiation sources, both laser and non-laser, by non-experts for aesthetic and entertainment purposes. The Greek Atomic Energy Commission relied on the ISO 31000:2018 framework to manage the public exposure risk to such cases. Risk was evaluated as (1) intolerable for lasers and intense pulsed light sources at aesthetic procedures and in the case of laser pointers, (2) severe for lasers at laser shows and (3) moderate for light-emitting diodes (LEDs) at aesthetic procedures, home-use intense pulsed light sources/LEDs and laser/LED projectors. Operators' training, public awareness campaigns, intensive market surveillance actions and the enhancement of the regulatory framework have been proposed as risk treatment/control measures and have been prioritised in this order, according to their effectiveness in reducing the exposure risk and their urgency of implementation. The Greek Atomic Energy Commission developed public awareness campaigns regarding exposure safety to laser and non-laser light sources at aesthetic procedures and the use of laser pointers.

Etched characteristics of nanoscale TiO2 using C4F8-based and BCl3-based gases

TiO2 is a material used in various fields such as electronics, optics, environment, etc. For the application to electronic and optical devices, TiO2 needs to be patterned using reactive ion etching using halogen-based gases. In this study, a TiO2 masked with ACL pillar pattern was etched using two types of gases namely C4F8-based (C4F8/SF6/Ar) and BCl3-based (BCl3/CF4/Ar), and the effect of etch gas and asynchronous pulsing (separated source power ON time and bias power ON time in a pulse period) on the etch properties such as the etch rates, etch selectivity, and aspect ratio dependent etching (ARDE) were investigated. The use of asynchronous pulsing with decreased bias pulsing ratio (high source power ON time and low bias ON time in a pulse period) improved the etch selectivity and ARDE possibly due to the lower sputter etching time after the removal of reacted species on the TiO2 surface and due to the more similar etch environment for different aspect ratio TiO2 features, respectively. The use of BCl3-based plasma showed higher etch selectivity over ACL compared to C4F8-based plasma, however, it showed the lower etch rate and more severe ARDE due to the stickiness of Cl compared to F to the sidewall during the etching of high aspect ratio TiO2.

Simple and compact high-power continuous-wave deep ultraviolet source at 261 nm based on diode-pumped intra-cavity frequency doubled Pr:LiYF4 green laser.

We report the recent progress on diode-pumped high-power continuous-wave Pr:LiYF4 (YLF) green laser and deep ultraviolet (DUV) laser generation via intracavity frequency doubling. Using two InGaN blue diode lasers as pump source to form a double-end pumping geometry, in this work, we have demonstrated a green laser at 522 nm with a maximum output power of 3.42 W, which is believed to be the highest power ever achieved in all-solid-state Pr3+ lasers in this specific spectral region. Moreover, by intracavity frequency doubling of the achieved green laser, we have further obtained a DUV laser at about 261 nm with a maximum output power of 1.42 W, which is far higher than previous results. The watt-level 261-nm laser paves the way towards the realization of simple and compact DUV source for a variety of applications.

Use of LANSCE Spallation Neutrons to Drive a Fusion Prototypic Neutron Source

A high-power neutron-producing spallation source is one option for meeting the mission of a fusion prototypic neutron source (FPNS). The Los Alamos Neutron Science Center at Los Alamos National Laboratory is uniquely suited to host such a source. A target concept has been developed that satisfies the initial goals established for an FPNS, as has a beam transport design that satisfies beam-on-target requirements for the concept. We discuss the potential impact of pulsed beam operation on radiation-induced changes in microstructure, as well as the ingrowth of calcium in steel alloys at a rate well beyond that expected in a fusion reactor first wall. A preliminary thermomechanical assessment shows the need to modify the target design to reduce temperatures and stresses in the tungsten target.

Research and Design of RF Ion Source Impedance Matching Network

The radio frequency (RF) ion source is the key component of the neutral beam injector to achieve high power and long pulse operation. The key technology is feeding RF power from the power source to the ion source and producing stable plasma. It is impossible to calculate the exact equivalent impedance of plasma during discharge, and the impedance will change with the change in discharge pressure and feed power. In order to transfer the maximum output power of the RF power source to the coil antenna of the ion source, an impedance-matching network must be added between the power source and the ion source. Four possible matching network structures are designed by the Smith diagram circle method, and two kinds of capacitor structures are calculated and analyzed. The influence of capacitance change on impedance matching state is analyzed, and the electrical parameters of capacitance under the two structures are compared. After comparison and analysis, the structure of the parallel capacitor is first, and then the series capacitor is selected. Finally, the plasma discharge can be stable through experiments. The research on the matching network is of great significance for the development and experimental operation of the RF feeding system of the high-power RF ion source in the future

A multifunctional nanoplatform based on Fe3O4@Au NCs with magnetic targeting ability for single NIR light-triggered PTT/PDT synergistic therapy of cancer

Although simultaneous photothermal therapy (PTT) and photodynamic therapy (PDT) have been proven to be beneficial for cancer treatment, high-power laser light sources, shallow penetration depth of light and especially activation by two different light sources make it difficult to be popularized in clinical cancer therapy. Herein, the novel multifunctional Fe3O4@Au nanocomposites (NCs) have been designed and synthesized, which simultaneously act as photothermal conversion agents (PCAs) and photosensitizers (PSs) for PTT/PDT synergistic therapy of human cervical cancer (HeLa) cells using a single excitation light source. Under low-power 808 nm laser irradiation, photothermal conversion efficiency (PCE) of Fe3O4@Au NCs was as high as 39.22% and the cytotoxic singlet oxygen (1O2) could be simultaneously generated. In addition, Fe3O4@Au NCs showed relatively good biocompatibility and low cytotoxicity, which were ideal alternatives for nanotherapeutic agents for treatment of HeLa cells. Meanwhile, PTT only and PTT/PDT dual-modal therapeutic effects of Fe3O4@Au NCs on HeLa cells were compared. The experimental results confirmed that the near-infrared (NIR)-triggered PDT/PTT synergistic therapy of HeLa cells was more efficient due to the synergistic effect. Interestingly, Fe3O4@Au NCs with saturation magnetization (Ms) value of 66.5 emu/g possessed good magnetic responsivity, which could be collected easily with a magnet. The magnetic targeting of Fe3O4@Au NCs could effectively promote their accumulation at tumor sites, thus further enhancing the efficacy of PTT/PDT synergistic therapy of HeLa cells. This study provides a feasible paradigm for magnetic targeting-assisted PTT/PDT synergistic therapy of cancer cells under a single-wavelength excitation and opens up a novel direction for clinical cancer therapy.

Achieving High Quantum Efficiency Broadband NIR Mg4 Ta2 O9 :Cr3+ Phosphor Through Lithium-Ion Compensation.

Ultra-efficient broadband near-infrared (NIR) phosphor-converted light-emitting diodes (pc-LEDs) are urgently needed to improve the detection sensitivity and spatial resolution of current smart NIR spectroscopy-based techniques. Nonetheless, the performance of NIR pc-LED has severely limited owing to the external quantum efficiency (EQE) bottleneck of NIR light-emitting materials. Herein, a blue LED excitable Cr3+ -doped tetramagnesium ditantalate (Mg4 Ta2 O9 , MT) phosphor is advantageously modified through lithium ion as a key efficient broadband NIR emitter to achieve high optical output power of the NIR light source. The emission spectrum encompasses the 700-1300nm electromagnetic spectrum of first biological window (λmax = 842nm) with a full-width at half-maximum (FWHM) of ≈2280 cm-1 (≈167nm), and achieves a record EQE of 61.25% detected at 450nm excitation through Li-ion compensation. A prototype NIR pc-LED is fabricated with MT:Cr3+ , Li+ to evaluate its potential practical application, which reveals an NIR output power of 53.22mW at a driving current of 100mA, and a photoelectric conversion efficiency of 25.09% at 10mA. This work provides an ultra-efficient broadband NIR luminescent material, which shows great promise in practical applications and presents a novel option for the next-generation high-power compact NIR light sources.

Tunable ultra-narrow linewidth diode laser for multiple metastable rare gas pumping.

We present what we believe to be a novel external cavity feedback structure based on a double-layer laser diode array with volume Bragg grating (VBG). Diode laser collimation and external cavity feedback result in a high-power and ultra-narrow linewidth diode laser pumping source with a central wavelength of 811.292 nm, spectral linewidth of 0.052 nm, and output power exceeding 100 W, with external cavity feedback and electro-optical conversion efficiencies exceeding 90% and 46%, respectively. The temperature of VBG is controlled to tune the central wavelength from 811.292 nm to 811.613 nm, covering the Kr* and Ar* absorption spectra. We believe this is the first report of an ultra-narrow linewidth diode laser that can pump two metastable rare gases.

Polymer composition with phenanthrenequinone for recording relief holographic gratings

The formation of periodic reliefs of the thickness of photosensitive polymer layers after recording holographic gratings in them and stimulating material deformations by reversible plasticization in a non-solvent liquid is considered. The phenomenon was studied for the composition of a copolymer with side anthracene groups — phenanthrenquinone. Phenantrenquinone transfers the energy of electronic excitation to oxygen molecules entering through the open surface of the polymer layer which then cause the oxidation of anthracene fragments. Holographic gratings with a period of 2–5 μm were recorded by laser radiation at a wavelength of 532 nm in layers about 1 μm thick. The photoreliefs were formed during the subsequent swelling of the layer in the medium of a hydrocarbon developer. The photosensitized oxidation of the anthracene groups of the new polymer under the action of optical radiation in the spectral range 408–532 nm was studied using the electron absorption spectra. It is shown that approaching the excitation wavelength to the long-wavelength absorption maximum of phenanthrenquinone (410 nm) makes it possible to increase the sensitivity of the material layer by a factor of 15 compared to layers with methylene blue as a photosensitizer. It has been experimentally established that the amplitude of weak periodic reliefs of a deformation nature (height less than 0.01 μm), which appear immediately after the recording of holographic gratings, increases many times during the treatment of the layer with liquid hydrocarbon. Their maximum value reaches 25 % of the thickness of the recording layer. Presumably, the deformation of the inhomogeneously irradiated layer is stimulated by the transfer of the polymer material into a highly elastic state during its swelling. Photoreliefs are stable after drying. Their strength can be increased by photocrosslinking the material as a result of photodimerization of residual anthracene groups under uniform irradiation with light at a wavelength of 365 nm. The non-sinusoidality of the photorelief reduces the diffraction efficiency achievable with total reflection to values less than 0.20. The studied polymer composition can be used to form relief-phase diffractive optical elements by radiation in the blue-green region of the spectrum, provided by a number of high-power laser sources.

Advances in Orbital Angular Momentum Lasers

As we celebrate 30 years since light's orbital angular momentum (OAM) was connected to its spatial structure, we reflect on the advances made in fundamental science and applications alike. A driving trend in recent times has been the creation of OAM directly from lasers, for potentially tuneable, compact and high-power sources of OAM light. In this tutorial style review we give a summary of the basics of OAM and its creation at the source, pointing to the seminal advances that have been made, the present state-of-the-art, and the open challenges that remain.

Detection of the minimum concentrations of α-lactose solution using high-power THz-ATR spectroscopy.

Terahertz (THz) technology has emerged as a promising tool for the qualitative and quantitative identification of markers containing major diseases, enabling early diagnosis and staged treatment of diseases. Nevertheless, the detection of water-containing biological samples is facing significant challenges due to limitations in high-power THz radiation sources and high-sensitivity detection devices. In this paper, we present a designed and constructed set of Terahertz-Attenuated Total Reflection (THz-ATR) spectrometer for high-sensitivity detection of liquid biological samples, which can dynamically maintain the signal-to-noise ratio (SNR) of THz detection signal of liquid biological samples at 40-60dB. Our high-power THz-ATR spectroscopy can identify and quantitatively detect α-lactose aqueous solution with a minimum concentration of 0.292mol/L. Moreover, we observed that the rate of change in the absorption peak position varied greatly between high and low concentration samples. Our high-power, high-sensitivity THz-ATR spectroscopy detection provides a rapid, accurate, and low-cost method for detecting disease markers such as blood and urine indicators. Additionally, this approach offers new perspectives for the refinement and in-depth detection of biomedical samples.