Ceramic Laser Research Articles

Solid-solution Er:(Sc,Y)2O3 transparent ceramics: Optical spectroscopy, inhomogeneous line broadening, C3i sites and mid-infrared laser operation

Rare-earth-doped transparent sesquioxide laser ceramics enable engineering of their gain bandwidths via solid-solution compositions exhibiting a strong inhomogeneous spectral line broadening. We report on a detailed spectroscopic study and the first mid-infrared laser operation of Erbium-doped yttria-scandia, (ScxY1−x)2O3, ceramics fabricated by vacuum sintering at 1750 °C from laser-ablated nanoparticles. The effect of the Sc fraction on the spectral and kinetic properties of Er3+ emission around 2.8 μm owing to the 4I11/2 → 4I13/2 is revealed. The inhomogeneous spectral line broadening leading to merging of individual Stark sub-levels of Er3+ multiplets is evidenced by low-temperature spectroscopy. An original method of quantifying the distribution of dopant Er3+ ions over C2 and C3i symmetry sites in the cubic bixbyite structure is suggested based on the transition probabilities derived by the Judd-Ofelt theory. In the parent Er:Y2O3 ceramic, the Er3+ ions nearly follow the ideal distribution with 3/4 of ions residing in C2 sites, and Sc addition skews it in favor of C3i sites. A continuous-wave Er:(Sc,Y)2O3 ceramic laser generated 312 mW at 2716 nm with a slope efficiency of 18.6 % and a laser threshold of 128 mW.

Development and characterization of novel Fe2+:ZnSexS1-x solid solution laser ceramics for mid-infrared laser application

In this study, Fe2+:ZnSexS1-x (0.6 ≤ x ≤ 1) solid solution laser ceramics with cubic crystal structures were prepared for the first time via hot pressing sintering, using FeSe, ZnSe, and ZnS powders. The resulting ceramics exhibit a unique combination of the optical and physical properties of Fe2+:ZnSe and Fe2+:ZnS. An increase in the ZnS content led to a blueshift in the maximum absorption spectra of Fe2+ ions and an enhancement in Vickers hardness. These findings suggest that Fe2+:ZnSexS1-x solid solution ceramics could serve as promising gain media for mid-infrared solid-state lasers, offering a novel approach for the development of directly pumped mid-infrared laser systems.

Advances in and Future Perspectives on High-Power Ceramic Lasers

Advancements in laser glass compositions and manufacturing techniques has allowed the development of a new category of high-energy and high-power laser systems which are being used in various applications, such as for fundamental research, material processing and inertial confinement fusion (ICF) technologies research. A ceramic laser is a remarkable revolution in solid state lasers. It exhibits crystalline properties, high yields, better thermal conductivity, a uniformly broadened emission cross-section, and a higher mechanical constant. Polycrystalline ceramic lasers combine the properties of glasses and crystals, which offer the unique advantages of high thermal stability, excellent optical transparency, and the ability to incorporate active laser ions homogeneously. They are less expensive and have a similar fabrication process to glass lasers. Recent developments in these classes of lasers have led to improvements in their efficiency, beam quality, and wavelength versatility, making them suitable for a broad range of applications, such as scientific research requiring ultra-fast laser pulses, medical procedures like laser surgery and high-precision cutting and welding in industrial manufacturing. The future of ceramic lasers looks promising, with ongoing research focused on enhancing their performance, developing new doping materials and expanding their functional wavelengths. The ongoing progress in high-power ceramic lasers is continuously expanding the limits of laser technology, therefore allowing the development of more powerful and efficient systems for a wide range of advanced and complex applications. In this paper, we review the advances, limitations and future perspectives of ceramic lasers.

First fluoride ceramics lasing at 605 nm at ambient temperature fabricated from chemically synthesized powders

Laser ceramics have emerged as promising candidates of solid-state laser gain media. However, most laser ceramics are currently focused on lasing in the infrared wavelength range. The very limited options of host materials and the increased optical scattering losses at shorter wavelengths within ceramics have greatly limited the development of visible laser ceramics. Here we report visible laser ceramics with a composition of 0.5%Pr3+,5%Y3+:SrF2, in which a visible (orange) laser oscillation at 605 nm has been successfully achieved at room temperature pumped by InGaN blue laser diodes with a maximum slope efficiency of 8.1%. The ceramics were fabricated by vacuum hot pressing (VHP) of wet-chemistry synthesized 0.5%Pr3+,5%Y3+:SrF2 powders, followed by hot isostatic pressing (HIP). It was found that the visible laser ceramics exhibited a lower optical scattering loss along the processing pressure direction of the VHP process, indicating a uniaxial anisotropy in optical transmission within the ceramics. To our best knowledge, the current work is the first report on visible laser ceramics lasing in the orange region at ambient temperature, fabricated from chemically synthesized powders, which could pave the way for future scientific research on and industrial applications of more sophisticated and cost-effective visible laser ceramics.

Instability and ultra-high frequency spectrum pulse train in passively Q-switched Yb:LuAG ceramic laser

Instability and ultra-high frequency spectrum pulse train in passively Q-switched Yb:LuAG ceramic laser

Modeling and preparation of additive-manufactured laser ceramics

ABSTRACT Additive manufacturing (AM) presents promising prospects for the production of laser ceramics, particularly those with composite structures. However, achieving uniform density within these ceramics is a formidable challenge, primarily due to the intrinsic limitations of uneven forces within the mold. This paper introduces the Density Spatiotemporal Evolution (DSE) model, a novel predictive tool designed to map the density distribution in laser ceramics throughout the AM process. The DSE model elucidates that ceramic density increases in proximity to the indenter and mold wall and reveals an oscillatory pattern in particle density during pressing. These insights have been corroborated through experimental measurements and simulation analyses. Leveraging the DSE model and a Simulated Annealing (SA) algorithm, an innovative AM process is proposed. The pressure exerted to each layer of ceramics is gradient distributed, i.e. 18, 18.36, 19.31, 22.08, 33.02 MPa. Preliminary experimental results indicate a significant enhancement in density uniformity, with an improvement of up to 45% in the optimized ceramics. The advancement promises to yield more homogeneous ceramic materials, potentially accelerating the progress of high-energy laser technology.

Dependence of the Raman vibration modes on structural properties of Tm:(ScxY1-x)2O3 laser ceramics with 0 ≤ x < 1.

We report on micro-Raman spectra of several mixed laser ceramics, i.e., 5at.%Tm:(ScxY1-xO2)3 with x = 0.121, 0.252, 0.489 and 5at.%Tm:Y2O3 ceramic. The samples were fabricated by solid-state pressureless consolidation of nanopowders produced by laser ablation of solid target in air flow. In particular, we studied the influence of Sc3+ content on the active vibration modes in terms of peak positions and shifts, linewidths and shapes: these parameters are relevant for the emission bandwidth of the laser medium. A shift towards higher frequencies is measured with the increase of the Sc3+ content in all samples in particular in (Tm0.048Y0.463Sc0.489O2)3 where the main Raman peaks are placed at 395, 494, 635 cm-1 while their shifts with Tm:Y2O3 are 22.6, 25.1, 40.1 cm-1, respectively. The assignment of the vibrational spectrum was obtained by density functional theory (DFT) with the Perdew-Burke-Enzerhof (PBE) exchange-correlation functional within the harmonic approximation framework.

Highly transparent Ce:Nd:YAG ceramic with good light conversion capacity for solar-pumped solid-state lasers

Developing a high quality ceramic laser gain medium for solar directly pumped solid state lasers is essential, and yet the light conversion efficiency of the gain media for solar pumping remains a challenge. In this study, Ce and Nd ions, co-doped YAG transparent ceramics with theoretical transmittance and stable Ce3+ valent state were developed, and revealed that the absorbed visible light and light conversion efficiency in Ce,Nd:YAG ceramics were 3.98 times and 1.34 times higher than those in widely reported Cr,Nd:YAG ceramics, respectively. A concentration matching principle between Ce3+ and Nd3+ ions in YAG was established, and a higher Nd3+ ion doping concentration with a relatively low Ce3+ concentration was favorable to improve both the light conversion efficiency and emission intensity at 1064 nm of Ce,Nd:YAG ceramics. Energy transfer efficiency from Ce3+ to Nd3+ of the 0.3 at.%Ce,1.5at.%Nd:YAG ceramic reached as high as 61.71% at room temperature. Surprisingly, it was further promoted to 64.31% at a higher temperature of 473 K. More excited electrons at the upper energy level of Ce3+ ion under the high temperature accounted for this novel phenomenon. This study proposes a new design strategy of gain materials for solar directly pumped solid state lasers.

A high stability and low noise passively Q-switched yellow-green laser with a Ti3C2Tx-PVA saturable absorber

An 808 nm laser diode (LD) end-pumped passively Q-switched Nd: YAG ceramic yellow green laser at 561 nm with high stability and low noise has been demonstrated, for the first time to our knowledge based on passively Q-switching with a Ti3C2Tx-polyvinyl alcohol (Ti3C2Tx-PVA) film, frequency selection and filtering with a Brewster polarizer (BP) and a birefringent crystal (BC), and intracavity frequency doubling with a LiB3O5 (LBO) crystal. The 1112 nm and 1116 nm wavelengths from the Nd: YAG ceramic and the number of longitudinal modes of 1123 nm fundamental frequency light were effectively suppressed by adopting BP and BC. At 5.1 W of the 808 nm LD pump power, the 561 nm-PQYG laser with a maximum average power of 75.5 mW, a maximum repetition rate of 610 kHz, and a narrowest pulse width of 41 ns were obtained, corresponding to an average power instability of ±0.29%, a repetition rate instability ±7.08%, a pulse width instability of ±4.67%, and a laser noise of 0.49% over a period of 4 h.

Understanding the consolidation mechanism of selective laser sintering/powder bed selective laser process of ceramics: Hydroxyapatite case

PurposeThe consolidation process and morphology evolution in ceramics-based additive manufacturing (AM) are still not well-understood. As a way to better understand the ceramic selective laser sintering (SLS), a dynamic three-dimensional computational model was developed to forecast thermal behavior of hydroxyapatite (HA) bioceramic.Design/methodology/approachAM has revolutionized automotive, biomedical and aerospace industries, among many others. AM provides design and geometric freedom, rapid product customization and manufacturing flexibility through its layer-by-layer technique. However, a very limited number of materials are printable because of rapid melting and solidification hysteresis. Melting-solidification dynamics in powder bed fusion are usually correlated with welding, often ignoring the intrinsic properties of the laser irradiation; unsurprisingly, the printable materials are mostly the well-known weldable materials.FindingsThe consolidation mechanism of HA was identified during its processing in a ceramic SLS device, then the effect of the laser energy density was studied to see how it affects the processing window. Premature sintering and sintering regimes were revealed and elaborated in detail. The full consolidation beyond sintering was also revealed along with its interaction to baseplate.Originality/valueThese findings provide important insight into the consolidation mechanism of HA ceramics, which will be the cornerstone for extending the range of materials in laser powder bed fusion of ceramics.

Wound Healing Evaluation after Gingival Depigmentation Using Ceramic Soft Tissue Trimming Bur Versus Diode Laser: Randomized Clinical Trial

Wound Healing Evaluation after Gingival Depigmentation Using Ceramic Soft Tissue Trimming Bur Versus Diode Laser: Randomized Clinical Trial

Passively Q-Switched Ho :YAG Ceramic Laser with a GaAs Saturable Absorber

Passively Q-Switched Ho :YAG Ceramic Laser with a GaAs Saturable Absorber

Comparative studies of spectroscopic properties and surface structure of solid solutions of CaF2:SrF2:YbF3 crystals and ceramics

The optical properties of laser ceramics based on 65CaF2:30SrF2:5YbF3 have been studied and compared with a single crystal of the same composition when exposed to 60Co γ-rays. The spectral characteristics of the non-irradiated samples were similar. During and after γ-ray irradiation of the 65CaF2:30SrF2:5YbF3 crystal and ceramic samples, Yb3+→Yb2+ transformations occur as well as configurationally Yb3+→Yb3+ transitions between the different states of the Yb3+ ions with the participation of the interstitial Fi ions. Our analysis of the state of the surface of the single crystal and nanoceramics showed that the roughness on the surface of the ceramics was improved, while on the surface of the single crystal it worsened when compared to its initial state.

3D Printing of Gradient-Doped Yb:YAG Laser Ceramics by Leveraging Active Mixing

Gradient-doped laser ceramics fabricated via 3D printing have great potential for high-power laser applications. However, it is challenging to produce such types of gain media because it is inconvenient to fabricate different component slurries prepared offline using traditional methods precisely. To address these issues, a facile approach for the additive manufacturing of high-power laser ceramics is proposed for gradient structure fabrication. First, a material-extrusion-based 3D printing device with a homemade active mixing module is developed to fabricate gradient-doped Yb:YAG(Y3Al5O12) laser ceramics using two slurries with different doping concentrations. Subsequently, the active mixing module is systematically investigated to obtain different Yb-doped concentrations of printing slurries with a uniform element distribution. By measuring the switching delay volume between different components, a proper volume adjustment enables the Yb concentration distribution of the green bodies to be consistent with the designed profile in the 3D process. Finally, multi-component (0–5–10–5–0 at% Yb:YAG) green bodies are printed, and experimental tests are conducted to evaluate the performance of these gradient-doped laser ceramics. The results show that the gradient-doped ceramic obtained 82.1% in-line transmittance at 1100 nm (4.6 mm thickness, along with the doping concentration gradient) and the average Yb ions diffusion distance across the interface fitted in the 20–30 μm range. Furthermore, a 1030 nm laser output with an output power of 4.5 W with a slope efficiency of 41.3% is achieved when pumped with a 940 nm laser diode. This study provides useful insights for developing various gradient rare-earth-doped laser ceramics for high-power laser applications.

Wavelength-tunable Tm:Y2O3 ceramic vortex laser with a changeable orbital angular momentum state.

Wavelength-tunable orbital angular momentum (OAM) lasers with controllable topological charges have the potential for serving as light sources for large-capacity optical communication by combining conventional wavelength division multiplexing (WDM) with OAM mode-division multiplexing (OAM-MDM). In this study, we demonstrate a wavelength-tunable Tm-bulk laser that can control OAM states in the 2-µm spectral range. The excitation conditions for different Laguerre-Gaussian (L G 0,l ) modes in a bulk laser cavity are theoretically determined by measuring the spatial propagation dynamics of the annular pump beam. As a proof-of-principle study, we experimentally generate OAM states of |ℏ| and |2ℏ| from a T m:Y 2 O 3 ceramic laser with a tunable emission wavelength using a Lyot filter (LF). The spatial properties of the scalar optical vortices are well conserved during wavelength tuning, indicating the feasibility of our approach for producing wavelength-tunable structured light. These OAM laser sources, which are characterized by their robustness and compactness, have potential applications in various areas such as optical communications, quantum optics, super-resolution microscopes, and more.

Effect of forming strategy on surface morphology and properties of zirconia ceramics formed by laser powder bed fusion

This paper investigates the effects of different forming processes on the surface morphology and dimensional accuracy of zirconia ceramics, and selects the optimal forming process for mechanical property analysis. A laboratory-built ceramic laser 3D printer was used to carry out the forming experiments on the specimens. Under the condition that only the forming process of the experimental target is changed, the effects of powder layering process, scanning spacing and scanning strategy on the surface morphology and properties of zirconia ceramics are investigated. The use of two powder spreading and scanning forming processes in the sample forming process effectively improved the forming defects of zirconia ceramics caused by powder splattering, and the zirconia ceramics had a better forming effect. Under this condition, the dimensional accuracy of the specimens increases and then decreases with the decrease of the scanning spacing, where the highest dimensional accuracy is obtained when the scanning spacing is 0.158 mm; among different scanning strategies, the best surface morphology is obtained by forming specimens with the island scanning strategy. In addition, the mechanical properties of the ceramics formed from zirconia showed that the Young's modulus and Vickers hardness of the samples increased by approximately 53.6 % and 15.7 %, respectively, compared to the traditional forming process.

Spectroscopy of thulium ions in solid-solution sesquioxide laser ceramics: Inhomogeneous spectral line broadening, crystal-field engineering and C3i sites

We present a detailed spectroscopic study of Tm3+ ions in stoichiometric and “mixed” (solid-solution) cubic (C-type, sp. gr. Ia3‾) sesquioxides R2O3 (RY, Lu, Sc or their mixture), with the goal of developing broadband-emitting gain media for ultrafast lasers at ∼2 μm. Evidence of a linear variation (increase) of the crystal-field strength when decreasing the ionic radius of the host-forming cation R3+ in the isostructrural R2O3 series is presented. The crystal-field splitting of Tm3+ multiplets is determined for C2 sites and justified using a barycenter plot, and the first evidence of C3i Tm3+ species is presented. A remarkable inhomogeneous spectral broadening for compositionally “mixed” sesquioxides (in particular with Sc3+) with respect to the parent compounds is revealed at low temperatures. It is proven that binary and ternary “mixed” R2O3 compounds form substitutional solid-solutions with a mixing of the host-forming cations at the atomic level. The stimulated-emission and gain cross-sections for the 3F4 → 3H6 Tm3+ transition are determined. Guidelines for material engineering of Tm3+-doped gain media for mode-locked 2-μm lasers are also provided.

Inhomogeneous spectral line broadening and site distribution in “mixed” Er:(Sc,Y)2O3 laser ceramics

Erbium-doped “mixed” yttria-scandia (ScxY1-x)2O3 transparent laser ceramics were fabricated by vacuum sintering at 1750 °C from laser-ablated nanoparticles. Their absorption and mid-infrared emission properties were studied. The addition of Sc3+ induces a strong inhomogeneous spectral line broadening, modifies the crystal field and affects the distribution of Er3+ ions over C2 and C3i symmetry sites. Due to their broadband emission properties, Er:(ScxY1-x)2O3 ceramics are appealing for 2.8-μm lasers.

Strontium fluorapatite (S-FAP) nano-grained laser ceramics

The use of large-sized, highly transparent polycrystalline strontium fluorapatite (S-FAP) ceramics could be a breakthrough in the high-power laser field due to its excellent laser gain properties. However, its hexagonal crystal structure makes it difficult to obtain laser quality in polycrystalline ceramics owing to birefringence. In this study, fully densified transparent Nd- and Yb-doped S-FAP ceramics with an average grain size of ∼100 nm can successfully be fabricated via liquid-phase nano-powder synthesis followed by spark plasma sintering, thereby achieving laser oscillation of the Nd:S-FAP ceramics for the first time. Furthermore, we elucidated the discrepancy in the emission properties between single-crystal and ceramics with randomly oriented crystal grains. We believe that these findings can provide important insights into the design and development for efficient non-cubic ceramic laser systems.

Passively Q-switched and broadly tunable continuous-wave operations of a 2-μm Tm3+:Lu2O3 ceramic laser upconversion pumped at 1.064 μm

We report passively Q-switched and broadly tunable continuous-wave operations of a trivalent thulium ion-doped Lu2O3 ceramic laser near 2 μm by employing upconversion pumping at 1 μm. Upconversion pumping was performed with a commercial 1064-nm Yb:fiber laser and nonlinear absorption of up to 41 % was obtained. In the continuous wave case, a four-mirror x-cavity generated as high as 257 mW of output power at 2.06 μm with a power slope efficiency of 12 % with respect to the incident pump power. Tuning performance was further investigated with a quartz birefringent tuning plate and broad, continuous tuning was obtained in the 1950–2090 nm wavelength range. In addition, passively Q-switched operation was demonstrated with a semiconductor saturable absorber, yielding stable, 4.15-μs-long pulses at the pulse repetition frequency of 28.8 kHz.