Yttrium Aluminum Garnet Crystals Research Articles

Ultrafast Laser Manipulation of In-Lattice Plasmonic Nanoparticles.

Plasmonic nanoparticles enable manipulation and enhancement of light fields at deep subwavelength scales, leading to structures and devices for diverse applications in optics. Despite hybrid plasmonic materials display remarkable optical properties due to interactions between components in nanoproximity, scalable production of plasmonic nanostructures within a single-crystalline matrix to achieve an ideal plasmon-crystal interface remains challenging. Here, a novel approach is presented to realize efficient manipulation of in-lattice plasmonic nanoparticles. Employing ultrafast-laser-driven plasmonic nanolithography, metallic nanoparticles with controllable morphology are precisely defined in the crystalline lattice of yttrium aluminum garnet (YAG) crystal. Through direct ion implantation, hybrid plasmonic material composed of nanoparticles embedded in a sub-surface amorphous YAG layer is created. Subsequently, femtosecond laser pulses guide formation and reshaping of plasmonic nanoparticles from the amorphous layer into the single-crystalline matrix along direction of light propagation, facilitated by a plasmon-mediated evolution of laser energy deposition. By tailoring resonance modes and optimizing the coupling between structured particle assemblies, a range of applications including polarization-dependent absorption and nonlinearity, controllable photoluminescence, and structural color generation is demonstrated. This research introduces a new approach for fabricating advanced optical materials featuring in-lattice plasmonic nanostructures, paving the way for the development of diverse functional photonic devices.

Synergistic effect of YAG particulate reinforcement on microstructural and thermo-mechanical properties of pressureless sintered MgAl2O4 spinel ceramic composites

Yttrium aluminum garnet (YAG) powders, synthesized through a partial wet chemical process, exhibit controlled morphology, high phase purity, and uniform homogeneity etc. This process involves the precipitation of aluminum ions onto Y2O3 particles. The transformation process of the Al-compound/Y2O3 precursor structure leads to the direct crystallization of pure YAG at 900 °C, passing through an intermediate stage where hexagonal YAH phase forms. A comprehensive study was conducted on the impact of preformed YAG as a reinforcing phase on the densification, mechanical, and thermo-mechanical properties of MgAl2O4-YAG composite, sintered under pressureless sintering in temperature range of 1500 °C–1600 °C. The inclusion of YAG particulate up to 5.0 wt% significantly enhances the densification, hardness, fracture toughness, flexural strength and high-temperature mechanical behavior of magnesium aluminate spinel (MAS) ceramics, however, increasing the YAG content beyond 5.0 wt% causes a reduction in these properties. The optimized addition of YAG particulate contributes to reducing the average grain size and refining the microstructure of the spinel ceramic matrix.

Broadband rapid-scanning phase-modulated Fourier transform electronic spectroscopy

We present a phase-modulated approach for ultrabroadband Fourier transform electronic spectroscopy. To overcome the bandwidth limitations and spatial chirp introduced by acousto-optic modulators (AOMs), pulses from a 1 µm laser are modulated using AOMs prior to continuum generation. This phase modulation is transferred to the continuum generated in a yttrium aluminum garnet crystal. Separately generated phase-modulated continua in two arms of a Mach-Zehnder interferometer interfere with the difference of their modulation frequencies, enabling physical under-sampling of the signal and the suppression of low-frequency noise. By interferometrically tracking the relative time delay of the continua, we perform continuous, rapid-scanning Fourier transform electronic spectroscopy with a high signal-to-noise ratio and spectral resolution. As proof of principle, we measure the linear absorption and fluorescence excitation spectra of a laser dye and various biological samples.

Effect of chemical action on shear thickening polishing of YAG

The shear-thickening polishing (STP) method, a flexible polishing technique developed in recent years, was utilized to obtain high surface quality of yttrium aluminum garnet (YAG) crystal effectively. The effect of polishing slurry pH value, which characterizes the chemical action between slurry and YAG crystal, on the material removal rate and surface roughness of YAG crystal was investigated, and the mechanism of the chemical action between YAG and slurry in STP process was revealed through X-ray photoelectron spectroscopy (XPS) analysis. The influence of polishing speed and abrasive concentration, which were relating with mechanical action, on the polishing effects was also studied. The experimental results show that when the pH value of the polishing slurry is lower than 11, the dissociation of chemical bonds and the formation of new bonds on the surface of the YAG crystal are predominantly found, resulting in a lower material removal rate. While the pH value of polishing slurry reaches 13, a reaction layer consisting of Al2SiO5 and Y2SiO5, which has lower hardness than abrasive, is formed on the surface, and this reaction layer can be removed by mechanical action efficiently. The surface roughness Sa decreases from 60 ± 10 nm to 0.38 ± 0.06 nm in 15 min with MRR reaches 117.30 nm/min, which is 4.3 times higher than that of chemical mechanical polishing. Based on the results of XPS analysis, the material removal mechanism of YAG polished by STP is proposed. As revealed by the results, STP with chemical action provide a high efficiency polishing method for the high surface quality YAG crystal.

Rapid Fabrication of Yttrium Aluminum Garnet Microhole Array Based on Femtosecond Bessel Beam

High-aspect-ratio microholes, the fundamental building blocks for microfluidics, optical waveguides, and other devices, find wide applications in aerospace, biomedical, and photonics fields. Yttrium aluminum garnet (YAG) crystals are commonly used in optical devices due to their low stress, hardness, and excellent chemical stability. Therefore, finding efficient fabrication methods to produce high-quality microholes within YAG crystals is crucial. The Bessel beam, characterized by a uniform energy distribution along its axis and an ultra-long depth of focus, is highly suitable for creating high-aspect-ratio structures. In this study, an axicon lens was used to shape the spatial profile of a femtosecond laser into a Bessel beam. Experimental verification showed a significant improvement in the high aspect ratio of the microholes produced in YAG crystals using the femtosecond Bessel beam. This study investigated the effects of the power and defocus parameters of single-pulse Bessel beams on microhole morphology and size, and microhole units with a maximum aspect ratio of more than 384:1 were obtained. Based on these findings, single-pulse femtosecond Bessel processing parameters were optimized, and an array of 181 × 181 microholes in a 400 μm thick YAG crystal was created in approximately 13.5 min. The microhole array had a periodicity of 5 μm and a unit aspect ratio of 315:1, with near-circular top and subface apertures and high repeatability.

PROSPECTIVE LITHIUM ALUMINOSILICATE GLASS-CERAMIC MATERIALS FOR PULSE RANGEFINDERS

The relevance of creating multi-functional nanosecond pulsed laser devices with a generation wavelength that lies in the conditionally eye-safe region of the spectrum of 1.5÷1.6 μm has been established. The prospects of using the mode of passive Q-switching when receiving powerful nanosecond laser pulses with a radiation divergence close to the diffraction one have been determined. Materials for shutters that function in the mode of passive Q-switching were analyzed: solid-state nonlinear optical materials based on single crystals of yttrium-aluminum garnet doped with cations of neodymium, chromium, vanadium and other Nd- or Yb-doped crystals in the wavelength range of 0.8–1.2 μm. The promising use of oxide single crystals activated by Co2+ ions in four-coordinated oxygen positions for MgAl2O4, LiGa5O8, LaMgAl11O19 has been confirmed. The feasibility of developing transparent glass-ceramics based on aluminomagnesium and lithium gallium spinel for pulsed ranging was determined, taking into account its commercial availability, the simplicity of the production technology, as well as the homogeneity of the distribution of the activator in the volume. The feasibility of creating a new type of nonlinear optical materials based on nanostructured heat-resistant lithium aluminosilicate glass ceramics with spinel nanocrystals activated by Co2+ ions under low-temperature heat treatment conditions, has been determined. The purpose and tasks of the work are formulated, which consist in justifying the choice of the system and compositions of glasses for obtaining glass-ceramic materials as a passive laser shutter for powerful lasers that operate at a wavelength of 1.54 μm and are characterized by high heat resistance. The choice of the lithium aluminosilicate system R2O – RO – RO2 – P2O5 – R2O3 – SiO2 based on phase-forming SiO2, Al2O3, Li2O, modifying K2O is substantiated; RO – MgO, ZnO, CaO, SrO, BaO components and a complex crystallization catalyst of P2O5, CeO2, TiO2, SnO2, ZrO2 and ZnO. The structural criteria for the glass matrix were formulated. Compositions of model glasses were designed taking into account the calculated parameters fSi > 0.22, Kсr ≥ 3.5, Ktr ≥ 2.1, and the probability of obtaining transparent glass-ceramic materials with a sitallized structure for pulse rangefinders was established on their basis.

Simultaneous label-free autofluorescence multi-harmonic microscopy driven by the supercontinuum generated from a bulk nonlinear crystal.

Nonlinear microscopy encompasses several imaging techniques that leverage laser technology to probe intrinsic molecules of biological specimens. These native molecules produce optical fingerprints that allow nonlinear microscopes to reveal the chemical composition and structure of cells and tissues in a label-free and non-destructive fashion, information that enables a plethora of applications, e.g., real-time digital histopathology or image-guided surgery. Because state-of-the-art lasers exhibit either a limited bandwidth or reduced wavelength tunability, nonlinear microscopes lack the spectral support to probe different biomolecules simultaneously, thus losing analytical potential. Therefore, a conventional nonlinear microscope requires multiple or tunable lasers to individually excite endogenous molecules, increasing both the cost and complexity of the system. A solution to this problem is supercontinuum generation, a nonlinear optical phenomenon that supplies broadband femtosecond radiation, granting a wide spectrum for concurrent molecular excitation. This study introduces a source for nonlinear multiphoton microscopy based on the supercontinuum generation from a yttrium aluminum garnet (YAG) crystal, an approach that allows simultaneous label-free autofluorescence multi-harmonic imaging of biological samples and offers a practical and compact alternative for the clinical translation of nonlinear microscopy. While this supercontinuum covered the visible spectrum (550-900 nm) and the near-infrared region (950-1200 nm), the pulses within 1030-1150 nm produced label-free volumetric chemical images of ex vivo chinchilla kidney, thus validating the supercontinuum from bulk crystals as a powerful source for multimodal nonlinear microscopy.

Coherent control of the photonic spin Hall effect by Er3+ ion concentration in an Er3+-doped YAG crystal

We theoretically investigate the effect of doped Er3+ ion concentration on the spin Hall effect (SHE) of light reflected from a Kretschmann-Raether (K-R) structure. In such a structure, an Er3+-doped yttrium aluminum garnet (YAG) crystal acts as the substrate. The excitation of surface plasmon resonance(SPR) leads to the enhancement of the spin splitting of the reflected beam in the resonance reflection dip. Due to the variation of electric dipole moment and energy level lifetime induced by Er3+ ion concentration, the spin-dependent transverse shift is sensitively dependent upon Er3+ ion concentration. Furthermore, under different concentrations of Er3+ ion, the intensity and detuning of the control field have different effects on the magnitude, sign and position of the transverse shift. More importantly, the photonic SHE can be significantly enhanced via choosing the suitable values of the control intensity and detuning at 15% Er3+ ion concentration. Therefore, our scheme may provide a basis for selecting suitable Er3+ ion concentration to enhance the SHE of light in future integrated systems.

Insight into Polishing Slurry and Material Removal Mechanism of Photoassisted Chemical Mechanical Polishing of YAG Crystals.

Yttrium aluminum garnet (YAG) crystals are an important gain medium in thin-sheet solid-state lasers, and their processing quality directly affects the performance of solid-state lasers. But it is difficult to achieve high efficiency and high quality of YAG crystals by traditional chemical mechanical polishing (CMP). In this study, we developed a new polishing slurry for photoassisted chemical mechanical polishing (PCMP) of YAG crystals. The polishing slurry is composed of peroxymonosulfate (PMS), manganese ferrite (MnFe2O4), alumina (Al2O3) abrasives, and deionized water. PCMP is conducted in an ultraviolet (UV) light environment. When employing this polishing slurry for PCMP processing of YAG crystals, the material removal rate (MRR) achieved 250 nm/min and the surface roughness achieved 0.35 nm Sa. The experiments verified that both UV light and MnFe2O4 can effectively activate PMS to produce active free radicals and further enhance the chemical action of the polishing slurry. X-ray photoelectron spectroscopy (XPS) analysis results indicated that active radicals reacted with the surface structure of the crystal and removed the aluminum-oxygen octahedron in large quantities from it. The structural defects reduced the surface hardness of the crystal, which means that active free radicals can modify the crystal surface materials.

Boosting Nd3+ emission in Nd/Al/Y co-doped silica glass by mid-range localized environmental manipulation

Improving the repetition frequency of high-energy lasers is vital to promote the development and application of high-energy lasers, and its key lies in finding the laser gain media with excellent thermal shock resistance and high emission cross-section. Rare-earth ion (RE3+)-doped silica glass, whose thermal shock parameter is 1.5 times higher than that of yttrium aluminum garnet (YAG) crystals, is expected to satisfy this criterion after enhancing the emission intensity of RE3+. Nevertheless, modulating the spectral properties of RE3+ in rigid silica glass networks poses a significant challenge. Herein, we propose a mid-range localized environmental manipulation approach, which dramatically changes the microscopic symmetry of RE3+ from amorphous to the desired crystal structures for emission enhancement. As a representative, Nd/Y/Al co-doped silica glasses were prepared and heat-treated for different durations to form different mid-range localized environments, which were demonstrated by transmission electron microscopy, electron paramagnetic resonance tests, and Judd-Ofelt theory analysis. The results show that Nd3+ enters the YAG structure in favor of its emission enhancement. After optimizing the mid-range local environment of Nd3+ to balance fluorescence enhancement with fluorescence quenching and Rayleigh scattering, the emission intensity increases by 300%. Our work suggests that the mid-range localized environmental manipulation approach is extremely promising for promoting the development of high-energy and high-repetition-rate lasers. Furthermore, this approach can be generalized to adjust the emission characteristics of other RE3+-doped glasses and fibers.

Nanoscale multi-beam lithography of photonic crystals with ultrafast laser

Photonic crystals are utilized in many noteworthy applications like optical communications, light flow control, and quantum optics. Photonic crystal with nanoscale structure is important for the manipulation of light propagation in visible and near-infrared range. Herein, we propose a novel multi beam lithography method to fabricate photonic crystal with nanoscale structure without cracking. Using multi-beam ultrafast laser processing and etching, parallel channels with subwavelength gap are obtained in yttrium aluminum garnet crystal. Combining optical simulation based on Debye diffraction, we experimentally show the gap width of parallel channels can be controlled at nanoscale by changing phase holograms. With the superimposed phase hologram designing, functional structures of complicated channel arrays distribution can be created in crystal. Optical gratings of different periods are fabricated, which can diffract incident light in particular ways. This approach can efficiently manufacture nanostructures with controllable gap, and offer an alternative to the fabrication of complex photonic crystal for integrated photonics applications.

Significant enhancement in laser damage resistance of YAG crystal surface by plasma etching.

The high-quality surface of an optical element is a prerequisite for a high-power laser system design. Yttrium aluminum garnet (YAG) crystal is one of the most important materials for solid-state laser active medium. Laser-induced damage threshold (LIDT) of the YAG crystals might substantially limit the maximum output power of the whole laser system. In this research, we show the novel possibility of significant LIDT enhancement via plasma etching of YAG crystal surface for picosecond laser pulse durations. The dependence of the LIDT on the etching depth was investigated. With the optimized etching conditions, the LIDT value was increased by more than three times and reached the intrinsic LIDT of the bulk crystal.

Application of EPR Spectroscopy for Investigation of Antisite Defectsin Yttrium-Aluminum Garnet

Paramagnetic Ce3+, Tb3+ and Ho3+ centers in the yttrium position in yttrium aluminum garnet (YAG) crystals investigated by the EPR spectroscopy. Along with the main EPR signals of Ce3+ and non-Kramers Tb3+ ions located in a regular environment a number of new centers with less lines intensity with different g-factors and zero-field splitting observed. The number of lines and the symmetry of these centers indicate that they belong to cerium and terbium ions, near which there are YAl antisite defects (Y3+ in octahedral positions of Al3+) or AlY (Al3+ in dodecahedral positions of Y3+). In addition to the main EPR signals of non-Kramers Ho3+ ions located in Y3+, a number of less intense lines with different parameters also attributed to antisite defects.

Influence of Air Annealing on Optical and Scintillation Properties of YAG:Pr,Ca

Single crystals of yttrium aluminum garnet (YAG) with Pr3+ and Ca2+ ions grown by the vertical Bridgman method are submitted to air anneal. The influence of this process on optical absorption, photo‐, and radioluminescence is investigated in a set of samples with different concentrations of Pr and Ca. Absorption induced by the heat treatment in the 300–600 nm range in YAG:Pr,Ca is discussed, in comparison with that in YAG:Ca crystals. Photo‐ and radioluminescence spectra in as‐grown and air‐annealed samples recorded at room temperature are discussed. The features of emission decrease at 5d–4f and 4f–4f transitions of Pr3+ ions after heat treatment are considered.

Infrared Stimulated Luminescence of Ce3+ Doped YAG Crystals.

In this study, the infrared optically stimulated luminescence (IRSL) of single crystals of Ce3+ doped yttrium aluminum garnet (YAG) was investigated for the first time. It was found that infrared stimulation of these crystals, following previous exposure to beta radiation, produces a strong luminescence signal. The highest luminescence efficiency was exhibited by the YAG crystal with 0.1% of Ce. With this crystal, it was possible to measure as low doses as 0.1 mGy. Moreover, IRSL is mainly related to the TL peak at a relatively high temperature of c.a. 175 °C, which leads to quite good stability of the signal in time. These properties create good prospects for potential applications of YAG:Ce in dosimetric radiation measurements.

ВЛИЯНИЕ РЕДКОЗЕМЕЛЬНЫХ ЭЛЕМЕНТОВ И РАДИАЦИИ НА СПЕКТРАЛЬНЫЕ СВОЙСТВА ИТТРИЙ-АЛЮМИНИЕВЫХ ГРАНАТОВ И ФОСФАТНЫХ СТЕКОЛ

The experimental results of radiation-optical studies of yttrium-aluminum garnet (YAG) crystals, non-activated and activated by rare earth ions (Y3Al5O12—TR3+), as well as phosphate glasses activated by Nd3+ ions are presented. It is shown that the main mechanisms of phonon scattering on point defects play a role in changing the radio- and thermoluminescence spectra. Keywords: radiation-optical, phosphate glass, impurity, rare-earth element, yttrium-aluminum garnet, point defect, thermoluminescence.

Light and spins in rare-earth doped garnets

Spin-dependent optical properties of garnet crystals and garnet based ceramics, doped with cerium and also, along with cerium, co-doped with gadolinium and/or terbium, were studied by the method of optically detected of magnetic resonance by monitoring luminescence. The intensity of photoluminescence excited by circularly polarized light in the absorption bands of Ce3+ proved to be useful for selective monitoring of the population of the spin sublevels of the Ce3+ ground state. It was shown that due to cross-relaxation between the cerium and gadolinium electron spin systems the intensity of Ce3+ emission can be used to detect magnetic resonance of Gd3+. High-frequency EPR allowed finding a family of non-Kramers Tb3+ centers in yttrium aluminum garnet crystals. The influence of the magnetic resonance of Tb3+ on the luminescence of Ce3+ was observed. This suggests a coupling between the Tb3+ and Ce3+ systems, which are promising for coherent information processing. In irradiated crystals and ceramics of cerium-doped gadolinium-gallium garnet, magnetic field stimulation of the recombination of radiation defects was found, that is, it was shown that the energy accumulated during irradiation can be released in an external magnetic field. A huge increase in the afterglow intensity in a magnetic field and magnetic memory effects of magnetic memory were explained by the influence of strong internal magnetic fields on spin-dependent recombination.

Wideband EPR spectroscopy of Y-=SUB=-3-=/SUB=-Al-=SUB=-5-=/SUB=-O-=SUB=-12-=/SUB=- : Ho-=SUP=-3+-=/SUP=- crystals

EPR spectra of Ho3+ impurity ions were recorded in single crystals of yttrium aluminum garnet (Y3Al5O12) in the frequency range of 114-170 GHz, at a temperature of 4.2 K. The measurement results indicate the substitution of Ho3+ ions for Y3+ ions in the dodecahedral position with D2 local symmetry. The magnitude of the g-factor, the hyperfine structure constant, and the energy interval between the main and the first excited nondegenerate sublevels of the main multiplet 5I8 are determined. Weak satellite signals have also been registered, the origin of which is associated with the formation of antisite defects in the environment of Ho3+ paramagnetic centers. Keywords: hyperfine interaction, rare earth ions, spin Hamiltonian, non-Kramers ion.

Широкополосная ЭПР-спектроскопия кристалла Y-=SUB=-3-=/SUB=-Al-=SUB=-5-=/SUB=-O-=SUB=-12-=/SUB=-:Ho-=SUP=-3+-=/SUP=-

EPR spectra of Ho3+ impurity ions were recorded in single crystals of yttrium aluminum garnet (Y3Al5O12) in the frequency range of 114-170 GHz, at a temperature of 4.2 K. The measurement results indicate the substitution of Ho3+ ions for Y3+ ions in the dodecahedral position with D2 local symmetry. The magnitude of the g-factor, the hyperfine structure constant, and the energy interval between the main and the first excited nondegenerate sublevels of the main multiplet 5I8 are determined. Weak satellite signals have also been registered, the origin of which is associated with the formation of antisite defects in the environment of Ho3+ paramagnetic centers.

A Distributed Bonding Interfacial Loss Characterizing Method of Composite Crystal Based on Optical Low-Coherence Domain Reflectometry

Composite crystals are the key component of high-power solid-state lasers. The bonding interfacial loss of composite crystal slabs is a critical parameter to evaluate the quality of the bonding interface. A distributed method based on optical low-coherence domain reflectometry is proposed to measure the bonding interfacial loss. Distance-related reflecting coupling loss (RCL) and tilt were analyzed and calibrated to ensure accuracy. The interfacial loss of a Yb:yttrium aluminum garnet (YAG)/YAG crystal was measured and demonstrated as an example. This distributed method solves the problem that the weak reflection of the bonding interface cannot be eliminated in the traditional transmitted insertion loss test.