High-power Light Research Articles

A Review On The He-Ne Laser System

Abstract: The first continuous-wave (CW) laser to be created was the He-Ne laser. Ali Javan and his colleagues W. R. Bennet and D. R. Herriott revealed the production of a cw He-Ne laser a few months after Maiman declared his invention of the pulsed ruby laser. Neon atoms are excited by helium atoms in this four-level gas laser. The laser light is produced by the neon's atomic changes. Red light with a wavelength of 632.8 nm is produced by these lasers' most popular neon transition. In addition to producing various UV and IR wavelengths, these lasers may also produce green and yellow light in the visible spectrum (Javan's first He-Ne operated in the IR at 1152.3 nm). It is feasible to make a given He-Ne's output work at a single wavelength by utilizing highly reflecting mirrors that are intended for one of these numerous possible lasing transitions.He-Ne lasers normally produce a few to tens of mW (milli-Watt, or 10−3 W) of power; they are not generators of high-power laser light. These lasers' extreme stability, both in terms of output light intensity (minimal jitter in power level) and wavelength (mode stability), is likely one of its most notable characteristics. He-Ne lasers are frequently used to steady other lasers for these reasons. They are also utilized in applications, like as holography, where mode stability is vital. He-Ne lasers dominated the market until the mid-1990s when they were manufactured for low-power uses, such as range finding, scanning, optical transmission, laser pointers, etc. However, due to lower costs, other types of lasers most notably semiconductor lasers seem to have emerged victorious in the recent rivalry. [30]

White Light Generation and Stability Analysis of High-Power Blue LDs with Remote YAG Phosphors

This paper presents a comprehensive analysis of white light generation and the associated aging dynamics using high-power blue laser diodes (LDs) combined with transmissive single crystal remote YAG phosphors. By systematically varying input currents (ranging from 0.6 A to 3 A) and phosphor thicknesses (250 μm and 500 μm), this study elucidates the optical and electrical characteristics of LD-phosphor systems under diverse operating conditions. The results highlight the system’s potential for stable and efficient white light generation, making it suitable for high-power lighting applications. Experimental setups included both single LDs and a 4 × 2 LD array. For the single LD, a peak optical output of 4.16 W was achieved at 3 A, corresponding to an initial luminous flux of approximately 700 Lm and a correlated color temperature (CCT) of 4653 K, with minimal color temperature shift observed during a 60 min aging process. The 4 × 2 LD array demonstrated consistent white light output across varying phosphor thicknesses, with maximum luminous fluxes of 1857 Lm at 1.4 A and 2622 Lm at 1.6 A for phosphor thicknesses of 250 μm and 500 μm, respectively. Importantly, the phosphor exhibited excellent thermal stability throughout the aging process, with the CCT maintained within a range of 4600 K to 5500 K. These findings underscore the reliability and applicability of LD-based white light systems in demanding high-power lighting environments, offering a promising alternative to conventional light sources for automotive, industrial, and specialized lighting applications.

Tailoring thermal behavior and luminous performance in LuAG:Ce films via thickness control for high-power laser lighting applications

Tailoring thermal behavior and luminous performance in LuAG:Ce films via thickness control for high-power laser lighting applications

Blacklight sintering of BaZrO3-based proton conductors

Acceptor-doped BaZrO3, a ceramic proton conductor, is well researched for use in solid oxide fuel cells due to its proton conductivity and chemical stability. A major drawback of the material is the difficulty of sintering as it requires high sintering temperatures and long heating times (> 1600 °C, 24 h). An emerging sintering technology to mitigate this challenge is blacklight sintering, which uses a high-powered blue or UV light source to heat ceramics extremely fast leading to short sintering times and reduced energy demand. In this work, BaZr0.8Y0.2O3-δ (BZY20) and BaZr0.8Y0.1Sc0.1O3-δ (BZY10Sc10) were blacklight-sintered with a high-power blue laser in under four minutes. Even though the resulting samples have a gradient from large to small grains and structurally disordered grain boundaries, the proton conductivity is comparable to conventionally sintered samples. Hence, blacklight sintering is a promising technology with the potential to sinter BaZrO3 much faster, while saving energy.

High power mid-infrared side-pump combiner with good thermal stability based on the point-by-point fusion splicing technique.

High-power mid-infrared fiber lasers, featuring superior beam quality and good power-scaling ability, have a few important applications in material processing, medical surgery, and molecule spectroscopy. The high-power pump light combiner, as one of the key elements for constructing a mid-infrared fiber laser, is crucial for the laser performance. While some advanced side-pump combiners based on fluoride fiber have been reported in recent literatures, the thermal stability of the fluoride fiber combiner, which is closely-related to its power-scaling capability, is a long-living challenge. In this work, we demonstrate a high-power mid-infrared side-pump combiner with improved thermal stability, realized using the point-by-point fusion-splicing technique between a silica fiber taper and a piece of Er-doped fluoride gain fiber. The developed combiner exhibits a high coupling efficiency of ∼90%, supporting highly-stable operation at an incident pump power of up to 60 W. Using this combiner, we constructed a continuous-wave mid-infrared fiber laser which can deliver stably 4 W output power at 2.8 µm without using active cooling system. At this lasing power, the maximum input pump power is limited to 20 W to prevent fiber end-facet degradation, which can be further improved with the use of endcaps. This remarkable thermal stability renders the combiner great application potentials in constructing compact, robust, high-power fiber lasers at mid-infrared wavelengths.

Prevalence and Diversity of Plant Parasitic Nematodes in Irish Peatlands

The prevalence of plant parasitic nematodes (PPN) in the Irish peatlands was investigated in five different peatland habitats—raised bog, cutover scrub/woodlands, fens and peat grasslands, which were further sub-categorised into fourteen different sub-habitats. Within the raised bog habitat were healthy bog hummock (HBH), healthy bog lawn (HBL), degraded bog hummock (DBH) and degraded bog lawn (DBL) and the fen habitats were fen peat (FP) and rich fen peat (R-FP). Cutover scrub or woodland habitat included cutover scrub rewetted (C-RW), cutover scrub non-rewetted (C-NRW), woodlands rewetted (W-RW) and woodlands non-rewetted (W-NRW). Grassland included wasted peat (WP), rough grazing (RG-I) and improved fen peat grassland (IFPG-RW and IFPG-NRW). Soil samples from peatlands were all collected between July and December 2023 when the temperature ranged from 12 to 20 °C. One half of each sample was used for molecular nematode analysis and the other half for morphological identification of nematodes. For the morphological identification, a specific nematode extraction protocol was optimised for peatland soils, and the extracted nematodes were fixed onto slides to be studied under a high-power light microscope. Subsequently, the other part of the soil was processed to isolate total DNA, from which the 18S rRNA gene was sequenced for the identification of nematode taxa. The extracted DNA was also used for randomly amplified polymorphic DNA (RAPD) fingerprinting analysis to determine banding patterns that could classify different bog habitats based on PPN random primers. Compared to that in the climax habitats (HBH, HBL, DBH, DBL, FP, R-FP), PPN prevalence was recorded as being higher in grasslands (WP, RG-I, IFPG-RW and IFPG-NRW) and scrub/woodland ecosystems (C-RW, C-NRW, W-RW, W-NRW). The results indicate that nematode populations are different across the various bog habitats. Emerging and current quarantine PPN belonging to the families Pratylenchidae, Meloidogynidae, Anguinidae and Heteroderidae were noted to be above the threshold limits mentioned under EPPO guidelines, in grassland and wooded peatland habitats. Future actions for PPN management may need to be considered, along with the likelihood that these PPN might impact future paludiculture and other crops and trees growing in nearby agricultural lands.

Detecting optical frequency in weak signal light using injection-induced frequency modulation.

In fiber-optic sensing, long-distance transmission and demodulation of weak signal light (SL) are critical. This study improves the system by relocating an external cavity tunable laser (ECTL) to the transmission end. Directly injecting the SL into the ECTL modulates the output light and uses the high-power ECTL light for transmission, reducing loss. At the demodulation end, an orthogonal Mach-Zehnder interferometer (MZI) and an H13C14N gas absorption cell (GAC) extract SL wavelength information. Results demonstrate effective modulation with SL intensity as low as 1 nW and a demodulation resolution of up to 10 MHz, offering significant improvements in long-distance fiber-optic sensing.

Greater than Five-Order-of-Magnitude Postcompression Temporal Contrast Improvement with an Ionization Plasma Grating.

High-intensity lasers require suppression of prepulses and other nonideal temporal structure to avoid target disruption before the arrival of the main pulse. To address this, we demonstrate that ionization gratings act as a controllable optical switch for high-power light with a temporal contrast improvement of at least 3×10^{5} and a switching time less than 500fs. We also show that a grating system can run for hours at 10Hz without degradation. The contrast improvement from an ionization grating compares favorably to that achievable with plasma mirrors.

Effect of highpower light mechanical properties of composites

Effect of highpower light mechanical properties of composites

New phase-construction phosphors ceramics for warm-white solid-state lighting: Orange-yellow-emitting (Lu,Gd)3(Sc,Al)5O12: Ce3+

Phosphor-converted white light-emitting diodes (pc-wLEDs) and phosphor-converted white laser diodes (pc-wLDs) are extensively utilized in lighting applications, with their quality and reliability heavily dependent on color converters. Recent progress in all-inorganic color converters, particularly phosphor ceramics (PCs), have markedly enhanced performance. However, due to the difficulty of managing emissive components, achieving warm white light with substantial red emission still remains challenging. In this work, a series of pure-phase Ce3+-activated garnet-structured solid-solution PCs, (Lu,Gd)3(Sc,Al)5O12: Ce (LGSAG: Ce), were fabricated using vacuum sintering technology for the first time. Through systematic analysis, it can be revealed that the addition of Gd3+ leads to a red shift in emission through changes in crystal-field splitting, whereas the inclusion of Sc3+ primarily focuses on improving the microstructure of the developed PCs. Particularly, the pc-wLED constructed from typical LGSAG: Ce PC generated significantly warmer light with a correlated color temperature (CCT) of 2916 K, compared to the 9557 K from LuAG: Ce PC. Meanwhile, under 40.0 W (15.7 W/mm2) blue laser excitation, the maximum luminous flux and luminescence efficiency of one typical LGSAG: Ce PG are 1172 lm and 29.3 lm/W, respectively. Therefore, the developed LGSAG: Ce PCs can show notable potential as color converters for future high-power warm-white solid-state lighting applications.

Highly efficient and thermally stable photonic ceramic by controllable and full crystallization from glass

Polycrystalline ceramics are promising for a diverse range of applications in solid state laser, lighting, scintillator and optical storage. Unfortunately, current ceramic elaborations involves strict and complex synthetic procedures such as ultra-high pressure and vacuum processing. Here, we realize the tune of MgAl2Si4O12 and Mg2Al4Si5O18 phase formation in a glass by controlling the two crystal nucleation and growth individually, and obtain a polycrystalline non-stoichiometric Mg2-x/2Al4-xSi5+xO18:Eu2+ translucent ceramic by virtue of complete and congruent crystallization of the glass. Microstructural characterizations verify that the resulting ceramic exhibits dense and closely stacked micrometer-scale crystallites with very thin grain boundary structure. Chemical composition analysis by energy dispersive X-ray spectrometry revels the grain's composition is highly deviated from the stoichiometric Mg2Al4Si5O18, with atomic ratio Mg/Al/Si of 1.00: 1.46: 2.70. The precipitated non-stoichiometric Mg2-x/2Al4-xSi5+xO18, structurally having infinite channels z = 0.25 or 0.75 sites that run parallel to the c-aix, provides an robust crystal-field environment for Eu2+ 5d-4f transition. As a consequence, the ceramic produces intense emission with photoluminescence quantum yield (PLQY) up to 90 %, and excellent thermal stability emission with 70.1 % emission intensity at 420 K relative to that at room temperature, demonstrating it can be applied in high power lighting application with improved light quality by employing the ceramic as a color converter. Moreover, the ceramic also exhibits thermally stimulated luminescence at temperature reaching up to 700 K, originating from the deep electronic traps in Mg2-x/2Al4-xSi5+xO18 lattice with estimated trap depth of 0.73eV and 0.97eV. We also demonstrate the ceramic is hopeful for optical information storage application as the storage information can be retain well without vulnerable by the fluctuations of external environments due to the deep traps.

High power lateral coupled InAs/GaAs quantum dot distributed feedback lasers grown on Si(001) substrates

High-quality single-frequency semiconductor lasers play a key role in silicon optical integrated systems. Combining high density 8-stacked quantum dot (QD) material and low–loss laterally coupled gratings, we here demonstrate a high output power, low noise, and insensitivity to light feedback 1.3 µm InAs/GaAs QD distributed feedback (DFB) laser grown on Si(001) substrates. For a QD DFB laser of a 3 × 1500 µm2 cavity, it exhibits a high single-mode output light power of up to 25 mW at 20 °C and 1.8 mW at 70 °C, respectively and maintains a stable single–mode operation in the entirely measured temperature range with a maximum side mode suppression ratio (SMSR) of 56.5 dB. Furthermore, the laser has an average relative intensity noise value low to –155.9 dB/Hz and a Lorentzian linewidth narrow to 243 kHz. In addition, the laser shows an insensitivity to optical feedback with a feedback level of –24.9 dB. Lastly, a 7-channel QD DFB laser array emitting at wavelengths from 1274.5 nm to 1290.0 nm are also exhibited with all SMSRs of higher than 45 dB. The results achieved here enable a practical single-frequency Si-based light source for the development of high-performance silicon photonic chips.

Robust and orange-yellow-emitting Sr-rich polytypoid α-SiAlON (Sr3Si24Al6N40:Eu2+) phosphor for white LEDs

ABSTRACT Nitrides and oxynitrides isostructural to α-Si3N4 (M-α-SiAlON, M = Sr, Ca, Li) possess superb thermally stable photoluminescence (PL) properties, making them reliable phosphors for high-power solid-state lighting. However, the synthesis of phase-pure Sr-α-SiAlON still remains a great challenge and has only been reported for Sr below 1.35 at.% as the large size of Sr2+ ions tends to destabilize the α-SiAlON structure. Here, we succeeded to synthesize the single-phase powders of a unique ‘Sr-rich’ polytypoid α-SiAlON (Sr3Si24Al6N40:Eu2+) phosphor with three distinctive Sr/Eu luminescence sites using a solid-state remixing-reannealing process. The Sr content of this polytypoid structure exceeds those of a few previously reported structures by over 200%. The phase purity, composition, structure, and PL properties of this phosphor were investigated. A single phase can be obtained by firing the stoichiometric mixtures of all-nitride precursors at 2050°C under a 0.92 MPa N2 atmosphere. The Sr3Si24Al6N40:Eu2+ shows an intense orange-yellow emission, with the emission maximum of 590 nm and internal/external quantum efficiency of 66%/52% under 400 nm excitation. It also has a quite small thermal quenching, maintaining 93% emission intensity at 150°C. In comparison to Ca-α-SiAlON:Eu2+, this Sr counterpart shows superior quantum efficiency and thermal stability, enabling it to be an interesting orange-yellow down-conversion luminescent material for white LEDs. The experimental confirmation of the existence of such ‘Sr-rich’ SiAlON systems, in a single-phase powder form, paves the way for the design and synthesis of novel ‘Sr-rich’ SiAlON-based phosphor powders with unparalleled properties.

Gravitational waves from high-power twisted light

Recent advances in high-energy and high-peak-power laser systems have opened up new possibilities for fundamental physics research. In this work, the potential of twisted light for the generation of gravitational waves in the high frequency regime is explored for the first time. Focusing on Bessel beams, novel analytic expressions and numerical computations for the generated metric perturbations and associated powers are presented. The gravitational peak intensity is shown to reach 1.44×10−5 W m−2 close to the source, and 1.01×10−19 W m−2 ten meters away. Compelling evidence is provided that the properties of the generated gravitational waves, such as frequency, polarization states, and direction of emission, are controllable by the laser pulse parameters and optical arrangements. Published by the American Physical Society 2024

Optical properties of Ce: GdYAG phosphor in glass with high quality LAS glass system and its application in laser illumination

Nowdays, the demand for high-power laser lighting applications is on the rise, however, phosphor in glass (PiG) prepared using conventional glass systems often experience damage under intense laser irradiation. To tackle this issue, we introduce a novel LAS glass system for phosphor encapsulation to create PiG, and by utilizing a spray coating technique, we blend PiG with high thermal conductivity sapphire to obtain phosphor in glass film (PiF), effectively improving laser irradiation resilience and optical characteristics. In this study, a novel LAS glass system (SiO2–Li2CO3–MgO–Al2O3–CaO–P2O5–K2O–ZrO2–Na2O) was utilized to encapsulate Ce:GdYAG phosphors to prepare a series of PiG and PiF. The glass system exhibits multi-directional interlocking lithium disilicate crystals, significantly enhancing the glass's strength and fracture toughness. There is no apparent interface reaction between the glass system and the phosphors, indicating effective protection of the phosphor particles. The PiF sample demonstrates a minor decrease of 5.2 % in internal quantum efficiency compared to the original phosphor, while boasting a high thermal conductivity of 7.4 W m−1 K−1. Notably, the optimized PiF shows remarkable enhancements with a saturation threshold of 4.37 W mm−2, surpassing PiG (1.668 W mm−2), and achieving LFmax of 424.41 lm and LEmax of 147.16 lm W−1. It features a high color rendering index (CRI) of 68.7 and low color correlated temperature (CCT) of 3646 K, significantly improving laser irradiation resistance and optical quality, making it a promising warm yellow laser illumination converter for diverse lighting applications.

BF2‐Bridged Azafulvene Dimer‐Based 1064 nm Laser‐Driven Superior Photothermal Agent for Deep‐Seated Tumor Therapy

AbstractSmall organic photothermal agents (PTAs) with absorption bands located in the second near‐infrared (NIR‐II, 1000–1700 nm) window are highly desirable for effectively combating deep‐seated tumors. However, the rarely reported NIR‐II absorbing PTAs still suffer from a low molar extinction coefficient (MEC, ϵ), inadequate chemostability and photostability, as well as the high light power density required during the therapeutic process. Herein, we developed a series of boron difluoride bridged azafulvene dimer acceptor‐integrated small organic PTAs. The B‐N coordination bonds in the π‐conjugated azafulvene dimer backbone endow it the strong electron‐withdrawing ability, facilitating the vigorous donor‐acceptor‐donor (D‐A‐D) structure PTAs with NIR‐II absorption. Notably, the PTA namely OTTBF shows high MEC (7.21×104 M−1 cm−1), ultrahigh chemo‐ and photo‐stability. After encapsulated into water‐dispersible nanoparticles, OTTBF NPs can achieve remarkable photothermal conversion effect under 1064 nm irradiation with a light density as low as 0.7 W cm−2, which is the lowest reported NIR‐II light power used in PTT process as we know. Furthermore, OTTBF NPs have been successfully applied for in vitro and in vivo deep‐seated cancer treatments under 1064 nm laser. This study provides an insight into the future exploration of versatile D‐A‐D structured NIR‐II absorption organic PTAs for biomedical applications.

BF2-Bridged Azafulvene Dimer-Based 1064 nm Laser-Driven Superior Photothermal Agent for Deep-Seated Tumor Therapy.

Small organic photothermal agents (PTAs) with absorption bands located in the second near-infrared (NIR-II, 1000-1700 nm) window are highly desirable for effectively combating deep-seated tumors. However, the rarely reported NIR-II absorbing PTAs still suffer from a low molar extinction coefficient (MEC, ϵ), inadequate chemostability and photostability, as well as the high light power density required during the therapeutic process. Herein, we developed a series of boron difluoride bridged azafulvene dimer acceptor-integrated small organic PTAs. The B-N coordination bonds in the π-conjugated azafulvene dimer backbone endow it the strong electron-withdrawing ability, facilitating the vigorous donor-acceptor-donor (D-A-D) structure PTAs with NIR-II absorption. Notably, the PTA namely OTTBF shows high MEC (7.21×104 M-1 cm-1), ultrahigh chemo- and photo-stability. After encapsulated into water-dispersible nanoparticles, OTTBF NPs can achieve remarkable photothermal conversion effect under 1064 nm irradiation with a light density as low as 0.7 W cm-2, which is the lowest reported NIR-II light power used in PTT process as we know. Furthermore, OTTBF NPs have been successfully applied for in vitro and in vivo deep-seated cancer treatments under 1064 nm laser. This study provides an insight into the future exploration of versatile D-A-D structured NIR-II absorption organic PTAs for biomedical applications.

15.5 W, pulsed 630 nm generation based on Raman fiber laser and second-harmonic generation.

We present a high-power, nanosecond 630 nm beam generation based on Raman conversion and second-harmonic generation (SHG). 116.2 W, single-mode 1080 nm fiber laser based on 10/125 µm optical fiber is used as a pump source for Raman conversion and the 1260 nm seed laser diode helps the amplification of third-order Raman conversion, which results in 63.7W at 1260 nm with 54.8% Raman conversion efficiency. SHG to 630 nm is based on type-I noncritical phase-matching conditions with bismuth triborate (BIBO) nonlinear crystal. The average power of 630 nm is 15.5 W at a repetition rate of 9.26 MHz, a pulse width of 16.0 ns, and a SHG efficiency of 24.4%. This result can facilitate the generation of a high-power visible light source with good beam quality at a specific wavelength.

A silicon diode–based optoelectronic interface for bidirectional neural modulation

The development of advanced neural modulation techniques is crucial to neuroscience research and neuroengineering applications. Recently, optical-based, nongenetic modulation approaches have been actively investigated to remotely interrogate the nervous system with high precision. Here, we show that a thin-film, silicon (Si)-based diode device is capable to bidirectionally regulate in vitro and in vivo neural activities upon adjusted illumination. When exposed to high-power and short-pulsed light, the Si diode generates photothermal effects, evoking neuron depolarization and enhancing intracellular calcium dynamics. Conversely, low-power and long-pulsed light on the Si diode hyperpolarizes neurons and reduces calcium activities. Furthermore, the Si diode film mounted on the brain of living mice can activate or suppress cortical activities under varied irradiation conditions. The presented material and device strategies reveal an innovated optoelectronic interface for precise neural modulations.

High-performance GeSi/Ge multi-quantum well photodetector on a Ge-buffered Si substrate.

This work demonstrates a high-performance photodetector with a 4-cycle Ge0.86Si0.14/Ge multi-quantum well (MQW) structure grown by reduced pressure chemical vapor deposition techniques on a Ge-buffered Si (100) substrate. At -1 V bias, the dark current density of the fabricated PIN mesa devices is as low as 3 mA/cm2, and the optical responsivities are 0.51 and 0.17 A/W at 1310 and 1550 nm, respectively, corresponding to the cutoff wavelength of 1620 nm. At the same time, the device has good high-power performance and continuous repeatable light response. On the other hand, the temperature coefficient of resistance (TCR) of the device is as high as -5.18%/K, surpassing all commercial thermal detectors. These results indicate that the CMOS-compatible and low-cost Ge0.86Si0.14/Ge multilayer structure is promising for short-wave infrared and uncooled infrared imaging.