Laser Excitation Research Articles

Investigating the Role of Primary Cilia and Bone Morphogenetic Protein Signaling in Periodontal Ligament Response to Orthodontic Strain In Vivo and In Vitro: A Pilot Study

Periodontal ligament (PDL) cells are crucial for mechanosensation and mechanotransduction within the PDL, yet the role of primary cilia in orthodontic force transmission has not been examined. While bone morphogenetic protein (BMP) signaling significantly influences ciliary function, its effect on cellular responses to mechanical stress has not been investigated. This study aims to investigate whether primary cilia and BMP signaling are involved in the periodontal ligament’s response to orthodontic tooth movement and the resultant mechanical strain. To visualize primary cilia, human PDL cells were cultured on glass-bottom dishes for five days, with a subset fixed daily, followed by immunostaining with anti-acetylated α-tubulin and Alexa Fluor 568 and imaging using a fluorescence microscope under 405 nm and 561 nm laser excitation. Human PDL cells were grown on Bioflex® culture plates and subsequently exposed to static tensile strains of 2.5%, 5%, 10%, 20%, on a FX-6000T™ Tension System for 24 h. RT-qPCR was performed to evaluate changes in expression of primary cilia via Ift88 expression, mechanotransduction via Cox2 expression, and BMP signaling-related genes. Histological specimens from orthodontically loaded and control human premolars were investigated for primary cilia and BMP signaling using immunohistochemistry and confocal microscopy. Primary cilia were observed in PDL cells from day one, with their incidence and length increasing over time alongside cell density. BMP signaling components, including upregulated genes such as Bmp7 (10.99–14.97 fold), Alk2 (3.19–5.45 fold), and Bmpr2 (1.64–8.40 fold), consistently responded to strain, while Cox2 and Ift88 showed differential regulation depending on strain intensity. In vivo, orthodontic movement activated BMP signaling and increased primary cilium incidence in the PDL. These findings indicate the potential role of primary cilia and BMP signaling in the mechanosensitivity of PDL cells under orthodontic forces. Further studies are required to understand the complex mechanotransduction mechanisms and role of these components in cellular adaptation during orthodontic tooth movement.

Research on Measurement Algorithm of Thermocouple Time Constant Under Multiple Incentive Experimental Conditions

ABSTRACTThe time constant is often an important indicator parameter to evaluate the response speed of thermocouples. However, in practical applications, the output signal suffers from interference and deformation due to the excitation signal not satisfying the desired step size, data transmission delay, and the effect of mechanical vibrations, which do not match the output response of the system of the same order. In addition, the measurement results are not reproducible due to the subjective influence of the manual measurement method. In this paper, we propose a method to compute the time constant. The output signal is modified by filtering and fitting to enable the automatic calculation of the time constant, and the parameters of the algorithm are discussed. We developed a thermocouple time constant measurement device using a water bath and laser excitation conditions, obtaining response signals from thermocouples with different wire diameters and laser powers. The results demonstrate the effectiveness of the proposed time constant calculation methods in accurately capturing the changing trend of thermocouples with different wire diameters and laser powers. These methods successfully meet the requirements for processing the dynamic response signals of thermocouples under various excitation conditions.

Outstanding pure green upconversion luminescence in LaZrTa3O11:Er3+/Yb3+ phosphors prepared by molten salt synthesis with B2O3 flux

AbstractHexagonal Er3+/Yb3+ co‐doped LaZrTa3O11 (LZTO) phosphor was prepared by molten salt synthesis with B2O3 flux. Holding temperature, holding time, solute and solvent ratio were regulated. The green upconversion luminescence (UCL) integral intensity of the optimal sample can reach 29.2% of β‐NaYF4:Er3+/Yb3+ under 980 nm laser excitation. This outstanding pure green UCL is due to the low phonon energy, Er3+/Yb3+ monolayer (2D) distribution, asymmetry of Er3+/Yb3+ doped lattice sites, and low oxygen vacancy. The maximum relative temperature sensitivity attains 0.01221 K−1 at 303 K by employing luminescence intensity ratio (LIR) technique. LZTO:Er3+/Yb3+ phosphor can be used in temperature sensing.

Combined dual-channel fluorescence depth sensing of indocyanine green and protoporphyrin IX kinetics in subcutaneous murine tumors.

Fluorescence sensing within tissue is an effective tool for tissue characterization; however, the modality and geometry of the image acquisition can alter the observed signal. We introduce a novel optical fiber-based system capable of measuring two fluorescent contrast agents through 2cm of tissue with simple passive electronic switching between the excitation light, simultaneously acquiring fluorescence and excitation data. The goal was to quantify indocyanine green (ICG) and protoporphyrin IX (PpIX) within tissue, and the sampling method was compared with wide-field surface imaging to contrast the value of deep sensing versus surface imaging. This was achieved by choosing filters for specific wavelengths that were mutually exclusive between ICG and PpIX and coupling these filters to two separate detectors, which allows for direct swapping of the excitation and emission channels by switching the on-time of each excitation laser between 780- and 633-nm wavelengths. This system was compared with two non-contact surface imaging systems for both ICG and PpIX, which revealed that the fluorescence depth sensing system was superior in its ability to resolve kinetics differences in deeper tissues that would normally be dominated by strong signals from skin and other surface tissues. Specifically, the system was tested using pancreatic adenocarcinoma tumors injected into murine models, which were imaged at several time points throughout tumor growth to its diameter. This demonstrated the system's capability to track longitudinal changes in ICG and PpIX kinetics that result from tumor growth and development, with larger tumors showing sluggish uptake and clearance of ICG, which was not observable with surface imaging. Similarly, PpIX was quantified, which showed slower kinetics over different time points, and was further compared with the wide-filed imager. These results were further validated through depth measurements in tissue phantoms and model-based interpretation. This fluorescence depth sensing system can be used to sample the interior blood flow characteristics by ICG sensing of tissue as deep as 20mm into the tissue with sensitivity to kinetics that are superior to surface imaging and may be combined with other imaging modalities such as ultrasound to provide guided deep fluorescence measurements.

Eutectic phosphor for high‐power excitation

AbstractHigh‐power blue‐emitting laser diodes have been used in projectors and lighting systems as excitation sources for yellow‐emitting phosphors. These phosphors must be robust and should not exhibit thermal quenching. In this work, we developed a durable eutectic phosphor consisting of single‐crystal Ce‐doped yttrium aluminum garnet (Ce:YAG) phosphor and Al2O3 (sapphire), with a thermal conductivity greater than 20 W/(m·K). This eutectic phosphor is named EPOCH‐Neo. EPOCH‐Neo specimens were cut from a large crystal substrate prepared by an edge‐defined film‐fed growth method. We evaluated the optical properties of EPOCH‐Neo specimens and the optical uniformity of an EPOCH‐Neo substrate. In addition, to control the chromaticity, the Y‐sites of Ce:YAG were doped with Gd at concentrations as high as 50% and the chromaticity and thermal characteristics of the resultant phosphors were evaluated. Moreover, the characteristics of a device composed of EPOCH‐Neo on a heatsink under blue laser excitation were examined. The results showed that EPOCH‐Neo is a durable phosphor suitable for use in high‐power‐excitation applications.

Enhanced Quantum Efficiency via Co-Substitution in Red-Emitting Phosphor Sr2[MgAl5N7] : Eu2+ for Advanced Spectroscopic Applications Including Laser Displays with Ultra-High Luminescence Saturation Threshold.

In order to obtain novel and more efficient red light-emitting materials, a series of Sr2[Mg1-xLixAl5-xSixN7] : 0.01Eu2+ (SMAN-xLS, 0≤x≤0.5) red phosphors were devised and successfully synthesized via the high temperature solid state reaction and the effects of the co-substitution of [Mg-Al]5+ by [Li-Si]5+ on structural and luminescence properties is investigated in detail. A series of powder XRD data and Rietveld refinement indicate that [Li-Si]5+ co-substitution can successfully enter the Sr2[MgAl5N7] : 0.01Eu2+ (SMAN) lattice. With the entry of [Li-Si]5+ into the lattice, the substitution of Al3+ by Si4+ leads to the weakening of the nephelauxetic effect of the 5d level of Eu2+, which shifts the emission peak from 657 nm to 647 nm and reduces the excitation in the green region, i.e., lowers the absorption of green light. When the amount of [Li-Si]5+ co-substitution is x=0.1, the luminescence intensity and thermal stability of the sample are enhanced, in which the external quantum efficiency (EQE), reflecting the luminescence intensity, is elevated by 49.6 %. The increase in lattice rigidity gives rise to higher luminescence intensity, and the introduced trap levels for the compensation of luminescence enhances the thermal stability. Under blue laser excitation, the SMAN-0.1LS can achieve an ultra-high luminescence saturation threshold of 52.22 W/mm2, which is remarkably superior to other existing red phosphors, a breakthrough performance that has enormous potential for application in high-power laser display light sources. Cathodoluminescence (CL) characterization and measurements attest to the favorable CL properties of SMAN-0.1LS. By measuring the pressure-dependent luminescence of SMAN-0.1LS, the emission peak can be shifted from 650 nm to 702 nm with the increase of pressure, and the sensitivity dλ/dP is 5.07 nm/GPa, which is indicative of the potential application of this system as an optical pressure sensor.

Enhanced Quantum Efficiency via Co‐Substitution in Red‐Emitting Phosphor Sr2[MgAl5N7] : Eu2+ for Advanced Spectroscopic Applications Including Laser Displays with Ultra‐High Luminescence Saturation Threshold

AbstractIn order to obtain novel and more efficient red light‐emitting materials, a series of Sr2[Mg1−xLixAl5−xSixN7] : 0.01Eu2+ (SMAN‐xLS, 0≤x≤0.5) red phosphors were devised and successfully synthesized via the high temperature solid state reaction and the effects of the co‐substitution of [Mg−Al]5+ by [Li−Si]5+ on structural and luminescence properties is investigated in detail. A series of powder XRD data and Rietveld refinement indicate that [Li−Si]5+ co‐substitution can successfully enter the Sr2[MgAl5N7] : 0.01Eu2+ (SMAN) lattice. With the entry of [Li−Si]5+ into the lattice, the substitution of Al3+ by Si4+ leads to the weakening of the nephelauxetic effect of the 5d level of Eu2+, which shifts the emission peak from 657 nm to 647 nm and reduces the excitation in the green region, i.e., lowers the absorption of green light. When the amount of [Li−Si]5+ co‐substitution is x=0.1, the luminescence intensity and thermal stability of the sample are enhanced, in which the external quantum efficiency (EQE), reflecting the luminescence intensity, is elevated by 49.6 %. The increase in lattice rigidity gives rise to higher luminescence intensity, and the introduced trap levels for the compensation of luminescence enhances the thermal stability. Under blue laser excitation, the SMAN‐0.1LS can achieve an ultra‐high luminescence saturation threshold of 52.22 W/mm2, which is remarkably superior to other existing red phosphors, a breakthrough performance that has enormous potential for application in high‐power laser display light sources. Cathodoluminescence (CL) characterization and measurements attest to the favorable CL properties of SMAN‐0.1LS. By measuring the pressure‐dependent luminescence of SMAN‐0.1LS, the emission peak can be shifted from 650 nm to 702 nm with the increase of pressure, and the sensitivity dλ/dP is 5.07 nm/GPa, which is indicative of the potential application of this system as an optical pressure sensor.

Photoluminescence and Raman spectroscopy of wide bandgap semiconductors damaged by deep-UV laser irradiation

The effects of a pulsed, focused, deep-UV (4.66 eV) laser on wide and ultra-wide bandgap semiconductors were investigated with photoluminescence (PL) and Raman spectroscopy. Three semiconductor single crystals were studied: silicon carbide (6H-SiC), gallium nitride (GaN), and gallium oxide (β-Ga2O3). Atomic emission lines from neutral Ga or Si were observed during the laser-damage process. For all three semiconductors, PL mapping (3.49 eV laser excitation) of the damaged material revealed visible emission bands in the 2.6–2.8 eV range, attributed to point defects. Raman spectra (2.33 eV excitation) showed a reduction in the Raman peak intensities in the damaged region, along with weak PL bands around 1.9–2.1 eV.

Fine-structure changing collisions in 87Rb upon D2 excitation in the hyperfine Paschen-Back regime

Abstract We investigate fine structure changing collisions in 87Rb vapour upon D2 excitation in a thermal vapour at 75 ∘C; the atoms are placed in a 0.6 T axial magnetic field in order to gain access to the hyperfine Pashen-Back regime. Following optical excitation on the D2 line, the exothermic transfer 5P 3 / 2 → 5P 1 / 2 occurs as a consequence of buffer-gas collisions; the 87Rb subsequently emits a photon on the D1 transition. We employ single-photon counting apparatus to monitor the D1 fluorescence, with an etalon filter to provide high spectral resolution. By studying the D1 fluorescence when the D2 excitation laser is scanned, we see that during the collisional transfer process the m J ′ quantum number of the atom changes, but the nuclear spin projection quantum number, m I ′ , is conserved. A simple kinematic model incorporating a coefficient of restitution in the collision accounted for the change in velocity distribution of atoms undergoing collisions, and the resulting fluorescence lineshape. The experiment is conducted with a nominally ‘buffer-gas free’ vapour cell; our results show that fine structure changing collisions are important with such media, and point out possible implications for quantum-optics experiments in thermal vapours producing entangled photon pairs with the double ladder configuration, and solar physics magneto-optical filters.

Multifunctional Near-Infrared Luminescence Performance of Nd3+ Doped SrSnO3 Phosphor

The phosphors with persistent luminescence in the NIR (near-infrared) region and the NIR-to-NIR Stokes luminescence properties have received considerable attention owing to their inclusive application prospects in the in vivo imaging field. In this paper, Nd3+ doped SrSnO3 phosphors with remarkable NIR emission performance were prepared using a high temperature solid state reaction method; the phase structure, morphology, and luminescence properties were discussed systematically. The SrSnO3 host exhibits broadband NIR emission (800–1300 nm) with absorptions in the near ultraviolet region. Nd3+ ions emerge excellent NIR-to-NIR Stokes luminescence under 808 nm laser excitation, with maximum emission at around ~1068 nm. The concentration-dependent luminescence properties, temperature dependent emission, and the luminescence decay curves of Nd3+ in the SrSnO3 host were also studied. The Nd3+ doped SrSnO3 phosphors exhibit exceptional thermal stability; the integrated emission intensity can retain approximately 66% at 423 K compared to room temperature. Most importantly, NIR persistent luminescence also can be observed for the SrSnO3:Nd3+ samples, which is in the first and second biological windows. A possible mechanism was proposed for the persistent NIR luminescence of Nd3+ based on the thermo-luminescence spectra. Consequently, the exciting results indicate that multifunctional NIR luminescence has been successfully realized in the SrSnO3:Nd3+ phosphors.

Prolonged Phase Segregation of Mixed-Halide Perovskite Nanocrystals in the Dark.

A critical issue hindering the potential applications of semiconductor mixed-halide perovskites is the phase segregation effect, wherein localized regions enriched with one type of halide anions would be formed upon continuous photogeneration of the excited-state charge carriers. These unexpected phases are capable of remixing again in the dark under the entropic driving force, the process of which is now being exclusively studied after the mixed-halide perovskites have arrived at the final stage of complete phase segregation. Here, we show that after the removal of laser excitation from a solid film of the mixed-halide perovskite nanocrystals (NCs) with partial phase segregation, the iodide- and bromide-rich regions can continuously grow in the dark for a prolonged time period of several minutes. We propose that this dark phase segregation is sustained by the local electric fields from the surface-trapped charge carriers, whose slow dissipation out of the mixed-halide perovskite NCs causes a delayed occurrence of the reversal phase remixing process.

Lead‐Sulfide‐Based Hybrid Inorganic‐Organic Superlattice Particles for Prominent Nonlinear Optical Absorption

AbstractSimultaneously optimizing nonlinear absorption coefficient and modulation depth is a considerable challenge for nonlinear optical materials. Here we present an effective solution through constructing PbS2‐based inorganic‐organic superlattice. PbS2/Cn superlattice particles are synthesized, where n (4, 6, and 8) denotes the number of carbon atoms in the organic component. First‐principles simulations indicate the formation of covalent bonds and van der Waals interaction between PbS2 unit and interlayer organic molecules. All samples exhibit strong nonlinear absorption under femtosecond laser excitation with a wavelength range between 515 nm and 900 nm, and the nonlinear absorption coefficient increases with interlayer distance. The optimized sample, PbS2/C8, demonstrates outstanding nonlinear absorption and substantial modulation depth under 800 nm (the third‐order nonlinear absorption coefficient βeff, 10449 ± 609 cm GW−1; modulation depth, 39.1%) and 900 nm (the fifth‐order nonlinear absorption coefficient γeff, 6465 ± 68 cm3 GW−2; modulation depth, 88.1%), which exhibits saturable absorption under 515 nm (βeff, ‐4932 ± 818 cm GW−1; modulation depth, 48.1%). It exhibits a small optical limiting threshold of 1.23 mJ cm−2. These performances surpass those of typical single‐/few‐layer metal chalcogenides. Structural and spectral analyses elucidate that the remarkable optical nonlinearity can be attributed to quantum confinement in the inorganic layer and the dielectric enhancement of the superlattice.

Faster Excited-State Intramolecular Electron Transfer from Perylenediimide Dianion Compared to Its Radical Anion.

The properties of the excited perylenediimide dianion (PDI2-∗) and its intramolecular electron transfer (ET) behavior were examined using femtosecond laser flash photolysis on PDI2- and PDI2--acceptor (A) dyads. Upon laser excitation, the dianion of PDI first generated a singlet (S1) state, followed by a triplet (T1) state. In all of the dyads, rate constants of the intramolecular ET from PDI2-∗ (S1) varied with the driving forces. Comparison of the PDI2-∗-A and PDI•-∗-A dyad systems revealed higher rate constants for the ET from PDI2-∗ than from PDI•-∗, which can be attributed to the difference in electronic coupling for the ET. These findings elucidate the previously unexplored photoinduced ET characteristics of PDI2-, thereby advancing the groundwork for photochemical studies of excited multi-ions and their applications in related materials.

Design and Performance of an InAs Quantum Dot Scintillator with Integrated Photodetector.

A new scintillation material composed of InAs quantum dots (QDs) hosted within a GaAs matrix was developed, and its performance with different types of radiation is evaluated. A methodology for designing an integrated photodetector (PD) with a low defect density and that is optically matched to the QD's emission spectrum is introduced, utilizing an engineered epitaxial InAlGaAs metamorphic buffer layer. The photoluminescence (PL) collection efficiency of the integrated PD is examined using two-dimensional scanning laser excitation. The detector response to 5.5 MeV α-particles and 122 keV photons is presented. Yields of 13 electrons/keV for α-particles and 30-60 electrons/keV for photons were observed. The energy resolution of 12% observed with α-particles was mainly limited by noise- and geometry-related optical losses. The radiation hardness of an InAs QDs hosted within GaAs and a wider band gap AlGaAs ternary alloy was studied under a 1 MeV proton implantation up to a 1014 cm-2 dose. The integrated PL responses were compared to evaluate PL quenching due to non-radiative defects. The QDs embedded in the AlGaAs demonstrated improved radiation hardness compared to QDs in the GaAs matrix and in the InGaAs quantum wells.

Photoremixing of Photosegregated Formamidinium/Cesium Lead Iodide/Bromide Thin Films under Pulsed Laser Excitation

Photoremixing of Photosegregated Formamidinium/Cesium Lead Iodide/Bromide Thin Films under Pulsed Laser Excitation

Selective Up‐ and Down‐Conversion Luminescence for Nonlinear Expansion of Unclonable Parameter Space

AbstractOptical physical unclonable functions (PUFs) have attracted considerable attention as an immediately exploitable cryptographic primitive for high‐level hardware security attributed to their potential for implementing a large parameter space through the incorporation of robust optical phenomena. However, previous optical PUFs primarily relied on linear and single‐channel optical processes, requiring an increase in the number of optical inputs (materials or wavelengths) in a monotonous manner to scale up challenge‐response pairs. Herein, an optical PUF capable of nonlinearly expanding the parameter space to enhance the cryptographic strength through the selective adjustment of up‐ and down‐conversion luminescence is introduced. The nonlinearity in the expansion of the parameter space originates from a random distribution of three types of microspheres, with their shells designed to exhibit various positional arrangements of upconversion nanoparticles and perovskite crystals. Because energy and photon interactions depend on their positional proximity and excitation power, adjusting the two excitation inputs into five power steps enables the single PUF to generate 30 unique cryptographic keys, which is 15 times greater than what a linear system can offer. The PUF also demonstrates high stability, maintaining its cryptographic performance when exposed to heat, moisture, and long‐term laser excitation, underscoring its practical applicability in security protocols.

CaCO3-encircled hollow CuS nanovehicles to suppress cervical cancer through enhanced calcium overload-triggered mitochondria damage

Cervical cancer stands is a formidable malignancy that poses a significant threat to women's health. Calcium overload, a minimally invasive tumor treatment, aims to accumulate an excessive concentration of Ca2+ within mitochondria, triggering apoptosis. Copper sulfide (CuS) represents a photothermal mediator for tumor hyperthermia. However, relying solely on thermotherapy often proves insufficient in controlling tumor growth. Curcumin (CUR), an herbal compound with anti-cancer properties, inhibits the efflux of exogenous Ca2+ while promoting its excretion from the endoplasmic reticulum into the cytoplasm. To harness these therapeutic modalities, we have developed a nanoplatform that incorporates hollow CuS nanoparticles (NPs) adorned with multiple CaCO3 particles and internally loaded with CUR. This nanocomposite exhibits high uptake and easy escape from lysosomes, along with the degradation of surrounding CaCO3, provoking the generation of abundant exogenous Ca2+in situ, ultimately damaging the mitochondria of diseased cells. Impressively, under laser excitation, the CuS NPs demonstrate a photothermal effect that accelerates the degradation of CaCO3, synergistically enhancing the antitumor effect through photothermal therapy. Additionally, fluorescence imaging reveals the distribution of these nanovehicles in vivo, indicating their effective accumulation at the tumor site. This nanoplatform shows promising outcomes for tumor-targeting and the effective treatment in a murine model of cervical cancer, achieved through cascade enhancement of calcium overload-based dual therapy.

Element-specific ultrafast lattice dynamics in FePt nanoparticles.

Light-matter interaction at the nanoscale in magnetic alloys and heterostructures is a topic of intense research in view of potential applications in high-density magnetic recording. While the element-specific dynamics of electron spins is directly accessible to resonant x-ray pulses with femtosecond time structure, the possible element-specific atomic motion remains largely unexplored. We use ultrafast electron diffraction (UED) to probe the temporal evolution of lattice Bragg peaks of FePt nanoparticles embedded in a carbon matrix following excitation by an optical femtosecond laser pulse. The diffraction interference between Fe and Pt sublattices enables us to demonstrate that the Fe mean square vibration amplitudes are significantly larger that those of Pt as expected from their different atomic mass. Both are found to increase as energy is transferred from the laser-excited electrons to the lattice. Contrary to this intuitive behavior, we observe a laser-induced lattice expansion that is larger for Pt than for Fe atoms during the first picosecond after laser excitation. This effect points to the strain-wave driven lattice expansion with the longitudinal acoustic Pt motion dominating that of Fe.

Optical spectroscopy of Nd3+-doped cadmium-rich borate glasses for near-infrared laser applications

The structural and spectroscopic properties of Nd3+-activated cadmium-rich borate (inverted) glasses are analyzed for near-infrared laser applications. The evaluation of the optimal glass-emitting sample by the Judd–Ofelt (JO) theory revealed JO parameter values of 4.56 × 10–20 cm2 (Ω2), 2.56 × 10–20 cm2 (Ω4), and 3.84 × 10–20 cm2 (Ω6). The Ω2 value, along with the experimental oscillator strength, suggested that the cadmium-rich borate glass could provide a more asymmetrical Nd3+ environment than other borate glasses like lithium-strontium-zinc, sodium-calcium, and lithium-lead-aluminum. In addition, the quality spectroscopy factor (χ = Ω4/Ω6) of 0.67 suggested that the 4F3/2 → 4I11/2 emission could be more suitable for laser applications. The stimulated emission cross-section (σp), theoretical quantum yield (ηQ), gain bandwidth (σp × Δλem), and optical gain (σp × τrad) laser parameters were close to those reported in sodium-calcium-borate, zinc-aluminum-barium-borate, and bismuth-borate glasses, while the non-radiative rate (WNR) and emission intensity saturation (IS) resulted to be lower. The emission spectra, under 808 nm laser excitation, displayed the featured neodymium 4F3/2 → 4I9/2,11/2,13/2 transitions, being the 4F3/2 → 4I11/2 (1058 nm) transition the more dominant one, in agreement with the χ parameter value. Nd3+ contents higher than 1.4 mol% led to emission quenching due to the increment of the cross-relaxation and/or energy migration rate. Such processes, according to the Inokuti–Hirayama model, were mainly mediated by electric dipole–dipole interactions within Nd–Nd clusters.

Laser light illuminant based on YAG: Ce phosphor ceramic with ultra-high luminance, stable output, and excellent heat dissipation

A hundred-watt level blue collimated laser is used to excite YAG: Ce phosphor ceramics to prepare a high-power white laser-based illuminant. A composite ceramic cooling device is prepared to reduce the operating temperature of YAG: Ce phosphor ceramics by using nano-silver to weld ceramics onto a copper block with a water-cooling device. Phosphor ceramics encapsulated with the above device can withstand the excitation of a 123W blue laser, and its output luminous flux value reaches 14600lm. The stable output time of the laser-based illuminant is over 30 minutes, and the operating temperature of the phosphor ceramic surface is only 270°C. Compared with the non-cooling device package, the luminous flux of the laser-based illuminant composed of phosphor ceramics packaged with the above structure is increased by 252.8%. The experimental results show that the composite ceramic cooling device can effectively reduce the operating temperature of phosphor ceramics which is an effective way to realize white laser-based illuminants over 10000lm.