Fabrication of tungsten-based optical diffuser using fiberform nanostructure via efficient plasma route.

Optical diffusion is an essential process used to manage photons in a wide range of photoelectric systems. This work proposes an approach to fabricate novel optical diffusers by a plasma-processing technique, using fiberform nanostructures formed by helium plasma irradiation and subsequent annealing. After an annealing procedure in the air for oxidation, the optical properties and the light-diffusing abilities of these nanostructured thin films were studied. In addition to the morphology analysis and total transmittance measurement, the diffusion efficiency of the optical diffusers was analyzed using a transmitted scatter distribution function (TDF). It was revealed that the diffusion efficiency of a device with an irradiation time of 30 minutes could reach 97%. The results demonstrate the potential of these nanostructured optical diffusers for various photoelectric applications.

Increased signal separation upgrade permits preliminary electron anisotropy measurements with Heliotron J multi-pass Thomson diagnostic.

A signal separation system is constructed on the multi-pass Thomson scattering system of Heliotron J to solve the problem of overlapping scattered light signals for the electron temperature anisotropy measurement. The phenomenon of overlapping scattered light signals is relieved by operating the signal separation system. A Raman scattering experiment is undertaken to verify the separation effect of the signal separation system. Two scattered light signals corresponding to two adjacent incidences of one laser shot were extended to 104 ns. Moreover, we applied the multi-pass Thomson scattering system with signal separation system to the electron temperature anisotropy measurement. No anisotropy was observed within the error bars in the initial experiment.

Verdet constant dispersion of magnesium fluoride for deep-ultraviolet and vacuum-ultraviolet Faraday rotators.

The Verdet constant dispersion in magnesium fluoride (MgF2) crystals was evaluated over a wavelength range of 190-300 nm. The Verdet constant was found to be 38.7 rad/(T·m) at a wavelength of 193 nm. These results were fitted using the diamagnetic dispersion model and the classical Becquerel formula. The fitted results can be used for the designing of suitable Faraday rotators at various wavelengths. These results indicate the possibility of using MgF2 as Faraday rotators not only in deep-ultraviolet regions, but also in vacuum-ultraviolet regions owing to its large bandgap.

Design of a dual scattering angle multi-pass Thomson scattering system with signal separation function on Heliotron J.

This paper proposes a design of dual scattering angles multi-path Thomson scattering system with a signal separation function to solve the overlapping phenomenon of scattered light signals and to increase the measurement accuracy for the investigation of anisotropic electron velocity distribution. Furthermore, an optical path design is proposed to demonstrate how overlapping scattered light signals can be separated by setting the optical path in a limited room with a compact layout, which makes the incident interval between two overlapping scattered light signals 1.7 times longer than that of our current system. The specific position of each optical component existing in the system is determined via a Gaussian beam analysis to avoid damage caused by overexpansion of spot size with the application of two cooperating image relay systems. Conversely, a polychromator is optimized by resetting the pass waveband of the interference filter combination to achieve high accuracy in electron temperature (Te) measurement corresponding to two scattering angles simultaneously.

Tb,Y:SrF2 crystal for efficient laser operation in the visible spectral region.

A Tb,Y:SrF2 crystal with high optical quality is grown using the temperature gradient technique. The spectroscopic and laser properties of the crystal in the visible spectral region are studied. A fluorescence lifetime of 5.6 ms is measured from the crystal, which is beneficial for laser operation with a low threshold. A continuous-wave Tb,Y:SrF2 laser delivers an output power of 259 mW at 545 nm, with a slope efficiency of 35.2%. To the best of the authors' knowledge, this is the first report on a Tb-doped SrF2 laser and represents the highest output power for visible alkaline-earth fluoride lasers. The limitations for power scaling are discussed.

Efficient diode-pumped Er:YAP master-oscillator power-amplifier system for laser power improvement at 2920†nm.

We report on the first demonstration of laser-diode-pumped master-oscillator power-amplifier (MOPA) system based on Er-doped bulk material working at 2920 nm. The relaxation oscillation at the beginning of the laser pulse from the Er:YAlO3 (YAP) oscillator was suppressed effectively when the pump frequency was increased to 140 Hz, as a result of the establishment of a three-level system. In the amplifier, the small signal gain of the Er:YAP strongly depends on pump duration and repetition frequency, and can reach the upper limit of parasitic oscillation. Further, 25.5 mJ of output pulse energy has been achieved from the amplifier at 150 Hz frequency (2.2 ms pump duration), with over 32% of optical-to-optical efficiency. Further improvement of the amplification ability of the MOPA system was discussed.

Specific methylation of (11R)-carlactonoic acid by an Arabidopsis SABATH methyltransferase.

MAIN CONCLUSION: An Arabidopsis S-adenosyl-L-methionine-dependent methyltransferase belonging to the SABATH family catalyzes the specific carboxymethylation of (11R)-carlactonoic acid. Methyl carlactonoate (MeCLA), found in Arabidopsis (Arabidopsis thaliana) as a non-canonical strigolactone (SL), may be a biosynthetic intermediate of various non-canonical SLs and biologically active as a plant hormone. MeCLA is formed from carlactonoic acid (CLA), but the methyltransferases (MTs) converting CLA to MeCLA remain unclear. Previous studies have demonstrated that the carboxymethylation of acidic plant hormones is catalyzed by the same protein family, the SABATH family (Wang et al. in Evol Bioinform 15:117693431986086. https://doi.org/10.1177/1176934319860864 , 2019). In the present study, we focused on the At4g36470 gene, an Arabidopsis SABATH MT gene co-expressed with the MAX1 gene responsible for CLA formation for biochemical characterization. The recombinant At4g36470 protein expressed in Escherichia coli exhibited exclusive activity against naturally occurring (11R)-CLA among the substrates, including CLA enantiomers and a variety of acidic plant hormones. The apparent Km value for (11R)-CLA was 1.46 µM, which was relatively smaller than that of the other Arabidopsis SABATH MTs responsible for the carboxymethylation of acidic plant hormones. The strict substrate specificity and high affinity of At4g36470 suggested it is an (11R)-CLA MT. We also confirmed the function of the identified gene by reconstructing MeCLA biosynthesis using transient expression in Nicotiana benthamiana. Phylogenetic analysis demonstrated that At4g36470 and its orthologs in non-canonical SL-producing plants cluster together in an exclusive clade, suggesting that the SABATH MTs of this clade may be involved in the carboxymethylation of CLA and the biosynthesis of non-canonical SLs.

Broadband mid-infrared amplified spontaneous emission from Er/Dy co-doped fluoride fiber with a simple diode-pumped configuration.

Er3+/Dy3+ co-doped double-clad ZBLAN optical fiber has been used to obtain amplified spontaneous emission (ASE) broadband light sources cladding-pumped by 980-nm multimode laser diode (LD) sources. It has been demonstrated that mid-infrared broadband emission extending from 2515 to 3735 nm was obtained by energy transfer between Er3+ and Dy3+. We experimentally investigated the optimum design of Er3+/Dy3+ co-doped ZBLAN fiber in terms of ion concentration, fiber length, pumping configuration, and pumping power. The ASE output power was more than 2.5 mW when the LD pump power was set at 5 W. To assess its potential for gas sensing applications, the fabricated ASE light source was used to successfully detect methane gas with concentrations at 1% and 5%. The simple and stable construction of our ASE light source is suitable for practical purposes.

Faraday Rotation of Dy2O3, CeF3 and Y3Fe5O12 at the Mid-Infrared Wavelengths.

The relatively narrow choice of magneto-active materials that could be used to construct Faraday devices (such as rotators or isolators) for the mid-infrared wavelengths arguably represents a pressing issue that is currently limiting the development of the mid-infrared lasers. Furthermore, the knowledge of the magneto-optical properties of the yet-reported mid-infrared magneto-active materials is usually restricted to a single wavelength only. To address this issue, we have dedicated this work to a comprehensive investigation of the magneto-optical properties of both the emerging (Dy2O3 ceramics and CeF3 crystal) and established (Y3Fe5O12 crystal) mid-infrared magneto-active materials. A broadband radiation source was used in a combination with an advanced polarization-stepping method, enabling an in-depth analysis of the wavelength dependence of the investigated materials' Faraday rotation. We were able to derive approximate models for the examined dependence, which, as we believe, may be conveniently used for designing the needed mid-infrared Faraday devices for lasers with the emission wavelengths in the 2-µm spectral region. In the case of Y3Fe5O12 crystal, the derived model may be used as a rough approximation of the material's saturated Faraday rotation even beyond the 2-µm wavelengths.

Compact deep ultraviolet frequency-doubled Tb:LiYF4 lasers at 272 nm.

A new laser system has been developed to generate coherent deep ultraviolet (DUV) radiation at 272 nm. The DUV lasers were produced via intra-cavity frequency doubling of the Tb3+:LiYF4 lasers emitting fundamentally at 544 nm. Continuous-wave (cw) and Q-switched operations were performed with a type I phase-matched ß-BaB2O4 nonlinear crystal. The cw operation produces 127 mW of averaged DUV output power. Passive Q-switched operation was realized by using Co2+:MgAl2O4 saturable absorbers. At an initial transmittance (excluding Fresnel reflections) of 99% at 544 nm, stable pulsed output at 272 nm with maximum single-pulse energy of 7.6 µJ and peak power of 6.1 W was obtained. Furthermore, by employing a smaller initial transmittance of 94.7%, we achieved maximum averaged DUV output power of 277 mW. The statistically averaged single-pulse DUV energy and peak power were estimated to be around 100 µJ and 320 W, respectively, which indicates great potential for this DUV laser system toward high energy and peak power.

Highly efficient Er:YAP laser with 6.9 W of output power at 2920†nm.

We report on the efficient high-power operation of a laser-diode-pumped Er3+-doped yttrium aluminum perovskite (Er:YAP) laser in the 3 µm spectral region at room temperature. 6.9 W of continuous-wave (CW) output power was obtained at 2920 nm. The slope efficiency was as high as 30.6% with respect to the absorbed pump power, which is close to the quantum defect limit (33.4%). To the best of our knowledge, this is the highest CW output power generated from 3 µm Er3+-doped solid state lasers at room temperature. Furthermore, our analysis has shown that more than 10 W of output power based on Er:YAP is possible by further mitigating the thermal lens effect.

40 kHz, 20 ns acousto-optically Q-switched 4 µm Fe:ZnSe laser pumped by a fluoride fiber laser.

An actively Q-switched mid-infrared Fe:ZnSe laser pumped by a continuous wave fluoride fiber laser has been developed. Stable operation with a pulse duration of 20 ns and a repetition rate of 40 kHz at 4 µm was achieved. The maximum peak power was 1.1 kW. The high-repetition rate, high-peak power nanosecond pulsed laser, which has been created for the first time, to the best of our knowledge, in an actively Q-switched Fe:ZnSe laser, should prove a suitable light source for laser processing and molecular sensing.

Verdet constant of potassium terbium fluoride crystal as a function of wavelength and temperature.

Potassium terbium fluoride KTb3F10 (KTF) crystal is a promising magneto-active material for creating multi-kilowatt average-power Faraday isolators operating at the visible and near-infrared wavelengths. Nevertheless, the key material's parameter needed for the design of any Faraday isolator-the Verdet constant, has not been comprehensively investigated yet. In this Letter, we report on measurement of the Verdet constant of the KTF crystal for wavelengths between 600 and 1500 nm and for temperatures ranging from 15 to 295 K. A suitable model for the Verdet constant as a function of wavelength and temperature has been developed and may be conveniently used for optimal design of KTF-based high-average-power Faraday isolators.

Efficient Pr:YAlO3 lasers at 622†nm, 662†nm, and 747†nm pumped by semiconductor laser at 488†nm.

We report laser operation of Pr:YAlO3 pumped by a frequency-doubled optically pumped semiconductor laser. Continuous-wave laser oscillations at around 622 nm, 662 nm, and 747 nm were demonstrated in plano-concave or/and plano-plano cavities. The maximum slope efficiencies were found to be 37%, 35%, and 59%, respectively, which are record-high values for Pr:YAlO3 lasers. Furthermore, lasing at 622 nm was demonstrated at room temperature for the first time to the best of our knowledge.

A Case of Fusobacterium necrophorum without Lemierre's Syndrome Mimicking Acute Leptospirosis.

Jaundice, conjunctival hyperemia, and acute kidney injury (AKI) are the characteristics of leptospirosis. However, it is not well known that Fusobacterium necrophorum infection can have a clinical picture similar to that of leptospirosis. A 38-year-old man was admitted with jaundice, conjunctival hyperemia, and AKI for 7 days. Chest CT scan showed multiple pulmonary nodules, atypical for leptospirosis. We started treatment with IV piperacillin-tazobactam and minocycline. He became anuric and was urgently started on hemodialysis on the second hospital day. Later on, blood cultures grew Fusobacterium necrophorum and other anaerobic bacteria. Antibody and PCR assays for Leptospira were negative. We narrowed the antibiotics to IV ceftriaxone and metronidazole. He responded well to the treatment and was discharged on the 18th hospital day. F. necrophorum infection is known to cause mixed infection with other anaerobic bacteria. The resistance of many anaerobic bacteria continues to progress, and F. necrophorum itself sometimes produces ß-lactamase. This case highlights the potential risks of using penicillin before diagnosis of leptospirosis.

2.92-µm high-efficiency continuous-wave laser operation of diode-pumped Er:YAP crystal at room temperature.

Mid-infrared lasers have attracted attention for application to the fields of medicine and industry. In this study, we demonstrate continuous-wave laser operation of a diode-pumped 5 at % Er-doped YAlO3 (YAP) single-crystal lasing at 2.92 µm with near-quantum-defect slope efficiency at room temperature. A high slope efficiency of 31% is achieved with a maximum output power of 0.674 W for a cavity length of 18 mm and an output coupler transmittance of 2.5%. This efficiency is 94% of the theoretical quantum-defect efficiency. Our results indicate that Er:YAP lasers can potentially be utilized to realize high-power mid-IR lasing.

Magneto-optic pyrochlore ceramics of Tb2Hf2O7 for Faraday rotator.

In the first demonstration of the Faraday effect in an optical-grade Tb2Hf2O7 (THO) ceramic, its optical properties and the Verdet constant's wavelength dependence were evaluated at room temperature. The transmittance loss of this material was equally low as for the terbium gallium garnet, a well-known magneto-optic material. The Verdet constant at 1064 nm was 50.4 rad/Tm, which was 1.4 times greater than that of the terbium gallium garnet. THO ceramics show great potential for use in Faraday devices in near-infrared laser applications.

Development of a high-speed full digital processing phase detector for interferometry.

This study describes the development of a fully digital-type phase detector for plasma interferometry. This detector functions even in situations in which the phase changes rapidly or the input signal is too small to derive the correct phase shift from the intermediate frequency (IF) signal. The detector directly converts the IF signal waveform of the interferometer to the phase shift signal by means of data processing in a logic circuit. Thus, the phase is derived from the whole waveform of the IF signal. The IF signal of the interferometer is converted to in-phase and quadrature-phase signals by Hilbert transformation, processed by a digital low-pass filter, and converted to polar coordinates by a coordinate rotation digital computer algorithm to obtain the phase shift. A simulation of the high-speed full digital processing phase detector shows that a fringe jump does not occur unless the phase change rate exceeds 0.8 × 106 rad/s. This value is sufficiently large compared to the phase change velocity in rapid density increase resulting from a pellet injection. The phase conversion is simulated using a real IF signal from an interferometer measured with a Heliotron J device. The results show that the phase signal is correctly calculated by the full digital processing method from the IF signal, the phase derivation of which is typically difficult to obtain when using a conventional analog phase detector.

Sapphire/Nd:YAG composite by pulsed electric current bonding for high-average-power lasers.

As a new bonding technique for high-power laser optics, pulsed electric current bonding (PECB) of sapphire and Nd:YAG ceramics was demonstrated. The optical properties of the composite were measured, and its microstructure at the interface and laser performance was analyzed. The optical transmittance was equal to the theoretical value, and the transmitted wavefront was λ/3 (λ=633 nm); both are appropriate values for laser applications. The microstructural analysis indicated an absence of scattering sources such as pores or non-contact points at the sapphire/Nd:YAG interface, and the distance of yttrium diffusion into the sapphire was theoretically expected to be less than 10 nm, much smaller than that of ceramic materials bonded by conventional thermal diffusion techniques. The laser performance of the composite material showed an 18% higher output power with almost the same threshold power and slope efficiency as a Nd:YAG ceramic due to the sapphire-conductive cooling effect. This new PECB technique for different transparent materials has the potential to bond large aperture optical materials over 100 mm in diameter and could be especially effective for fabricating active laser media for high-average-power lasers having both high-pulse energy and high repetition rates.

Induction of subterahertz surface waves on a metal wire by intense laser interaction with a foil.

We have demonstrated that a pulsed electromagnetic wave (Sommerfeld wave) of subterahertz frequency and 11-MV/m field strength can be induced on a metal wire by the interaction of an intense femtosecond laser pule with an adjacent metal foil at a laser intensity of 8.5×10^{18}W/cm^{2}. The polarity of the electric field of this surface wave is opposite to that obtained by the direct interaction of the laser with the wire. Numerical simulations suggest that an electromagnetic wave associated with electron emission from the foil induces the surface wave. A tungsten wire is placed normal to an aluminum foil with a gap so that the wire is not irradiated and damaged by the laser pulse, thus making it possible to generate surface waves on the wire repeatedly.