Yttrium Gallium Garnet Research Articles

Optical investigations of coherence and relaxation dynamics of a thulium-doped yttrium gallium garnet crystal at sub-kelvin temperatures for optical quantum memory

Optical investigations of coherence and relaxation dynamics of a thulium-doped yttrium gallium garnet crystal at sub-kelvin temperatures for optical quantum memory

The effect of Ce concentration on the structural and optical properties of YGG:Ce phosphor

Y3(1-x) Ga5O12 phosphors doped with different Ce3+ concentration (with x = 0.005, 0.01, 0.02, 0.03, 0.04, 0.05) were prepared by sol-gel method. X-ray diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), scanning electron microscope (SEM), Infrared (IR) spectroscopy, photopluminescence (PL) and thermo-luminescence (TL) were used to characterize the phase structure and optical properties of the samples. XRD and XPS results reveal that the Ce3+ ions have entered into the YGG matrix and the lattice expansion is produced by the incorporation of Ce3+ ions. SEM analysis indicates the yttrium gallium garnet (YGG) phase has good quality, high purity and regular morphology after sintering at 1100 °C. IR spectrum analysis has confirmed the peaks with wave-numbers greater than 1000 cm−1are significantly reduced after sintering at 1100 °C. The results of TL glow curves show that three peaks with suitable trap depths exist in the phosphors and the maximum TL intensity of the phosphors is observed at x = 0.01. Optical absorption spectra obtained for the Ce3+doped YGG phosphors have illustrated the absorption bands at 298 and 424 nm are related to the Ce ions. The excitation and emission peaks of YGG:Ce phosphors are obtained at 443 and 522 nm respectively, corresponding to the 4f↔5d transition of Ce ions. The luminescence (both PL and TL) performance of phosphors strongly depend on the Ce3+ ions and YGG:Ce phosphor has the best luminescence performance when x = 0.01.

A Novel Synthetic Approach for the Preparation of Bulk Bi3Fe5O12 on the Y3Ga5O12 Core

In this study the bismuth iron garnet (Bi3Fe5O12; BIG) nanocrystals were obtained using non-thermodynamical approach. The hydrothermal synthesis of BIG was performed on the yttrium gallium garnet (Y3Ga5O12; YGG) substrate. For the hydrothermal synthesis of Y3Ga5O12 core the Ga2O3 and Y(NO3)3·6H2O starting materials were used. The final precursor solution was transferred to teflon container which was put inside the hydrothermal bomb and heated at 180 °C for 20 h. For the preparation of BIG shell on the YGG core the obtained Y3Ga5O12 particles were dispersed in distilled water using ultrasound, and then the citric acid, Bi(NO3)3·5H2O and Fe(NO3)3·9H2O were added under continuous stirring. Finally, the obtained solution was transferred to a teflon container which was put inside a hydrothermal bomb and heated at 180 °C for 20 h. The synthesis products were characterized by X-ray powder diffraction (XRD) analysis, scanning electron microscopy (SEM), transmission electron microscopy (TEM) with STEM module, and X-ray energy-dispersive spectroscopy (EDX) analysis. The obtained results clearly showed that the garnet Bi3Fe5O12 crystalline phase has formed.

Rational Design of a Nd3+‐Mn4+ Co‐doped Luminescent Thermometer: Towards High‐Sensitivity Temperature Sensing

AbstractHigh temperature sensitivity is an important development direction for luminescent thermometers, especially in the physiological temperature range. Herein, neodymium(III) and manganese(IV) ions were co‐doped into a yttrium gallium garnet host (YGG) and the relevant dopant concentrations were optimized in detail. The temperature‐dependent spectral survey indicates that when the temperature was above 240 K, the 2Eg→4A2g transition of Mn4+ and the 4F5/2→4I9/2 emission of Nd3+ show strong fluorescence quenching and gradual fluorescence enhancement, respectively. Such an apparent contrast mainly originates from the nonradiative cross‐relaxation between 2Eg (or 4T2g) and 4A2g states of Mn4+ and thermal coupling between the 4F5/2 and 4F3/2 levels of Nd3+, respectively. The obvious difference in fluorescence between the two luminescent ions leads to an excellent temperature sensing performance. The obtained relative sensitivity shows a maximum value at 280 K (7.90 % K−1) and maintains a magnitude above 5.00 % K−1 over the whole physiological temperature range. Moreover, the related temperature uncertainties are below 0.1 K from 298 K to 323 K, and the repeatability capability is larger than 98 %. The findings in this study offer a feasible approach to promote the sensing capability of temperature sensors by rationally designing co‐doping systems.

High-efficiency Er-doped yttrium gallium garnet laser resonantly pumped by a laser diode at 1.47 µm.

The spectroscopic and laser properties of an Er3+-doped yttrium gallium garnet crystal, Y3Ga5O12 (YGG), are studied. The stimulated emission cross section is 1.4×10-21cm2 at 1.65 µm. A continuous-wave laser resonantly pumped by a laser diode at 1.47 µm is demonstrated, delivering a maximum output power of 3.34 W. Benefiting from the low phonon energy of the YGG host, the corresponding slope efficiency is as high as ∼42%. To the best of our knowledge, this is the highest slope efficiency from the laser-diode resonantly pumped Er lasers at room temperature in the 1.6 µm spectral range.

Exploring impurity phases derived from the introduction of vanadium ions in yttrium gallium garnet

The associated impurity phases derived from the introduction of vanadium ions in yttrium gallium garnet (YGG) were investigated in detail. The XRPD data indicate that β-Ga2O3 is contained in all synthesized samples and YVO4 can be identified when the V-doped concentration above 0.5 at. %. The existence of β-Ga2O3 is related to the antisite defects usually contained in the garnet host, and the generation of YVO4 is mainly derived from its lower formation temperature in comparison to the garnet phase. The micro-area composition analysis further verifies the existence of impurity phases, and the X-ray computed tomography survey provides a more visualized spatial distribution of the YVO4 phase. Moreover, the fluorescence analysis manifests a more sensitive phase identification than the XRPD technique, and the YVO4 impurity phase can be detected even if the V-doped content is reduced to 0.2 at. %. Additionally, the evaluated V/(V + Y + Ga) ratios from structure refinement coincide well with the theoretical value in the low-doping section, and the slight deviation in the high doping part is mainly attributed to the volatilization of vanadium oxides. What discussed in this study offers a comprehensive analysis strategy for the detection of impurity phases originating from ion doping.

A far‐red‐emitting (Gd,Y)3(Ga,Al)5O12:Mn2+ ceramic phosphor with enhanced thermal stability for plant cultivation

AbstractAs for plants, far‐red (FR) light with wavelength from 700 nm to 740 nm is critical for processes of photosynthesis and photomorphogenesis. Light‐controlled development depends on light to control cell differentiation, structural and functional changes, and finally converge into the formation of tissues and organs. Phosphor converted FR emission under LED excitation is a cost‐effective and high‐efficient way to provide artificial FR light source. With the aim to develop an efficient FR phosphor that can promote the plant growth, a series of gadolinium yttrium gallium garnet (GYGAG) transparent ceramic phosphors co‐doped with Mn2+ and Si4+ have been fabricated via chemical co‐precipitation method, followed sintered in O2 and hot isostatic pressing in this work. Under UV excitation, the phosphor exhibited two bright and broadband red emission spectra due to Mn2+: 4T1 → 6A1 spin‐forbidden transition, and one of which located in the right FR region. And then, Ce3+ ions were co‐doped as the activator to enhance the absorption at blue light region and the emission of Mn2+. It turns out that the emission band of GYGAG transparent ceramic phosphors matches well with the absorption band of phytochrome PFR, which means they are promising to be applied in plant cultivation light‐emitting diodes (LEDs) for modulating plant growth. Besides, the thermal stability of this material was investigated systematically, and an energy transferring model involves defects was also proposed to explain the phenomenon of abnormal temperature quenching.

High-efficiency 3 μm Er:YGG crystal lasers.

By balancing energy transfer and thermal effects, we demonstrate efficient erbium-doped yttrium gallium garnet (Er:YGG) crystal lasers at a wavelength of 2.82-2.92μm for the first time, to the best of our knowledge. Associated with the influence of doping concentration on energy transfer and thermal effects, the Er3+ doping concentration was optimized to be 10at.%, and with the optimized crystal, the maximum continuous-wave output power was 1.38W, corresponding to the slope efficiency of 35.4% approaching the theoretical quantum limits. The thermal effects during the laser process were discussed. We believe that this work should be helpful for optimizing the erbium-doped gain for the 3μm laser and the development of 3μm lasers.

Dynamic control of refractive index during pulsed-laser-deposited waveguide growth

Engineering the optical properties of waveguides is important for the optimization of their guided optical mode characteristics. Here, we document the dynamic control of the refractive index and composition of crystalline films, via the substrate temperature, during pulsed-laser-deposition growth of Er(1%)-doped yttrium gallium garnet on -orientated single-crystal yttrium aluminium garnet. An increasing substrate temperature is observed to reduce the gallium content in the grown film, with a corresponding reduction of refractive index. We demonstrate the ability to accurately control the refractive index via this technique and use it to grow a complex multi-core crystal waveguide. Our results highlight the potential of using pulsed laser deposition to fabricate crystal films with bespoke optical properties and thus engineer passive and active waveguide devices in situ.

Controlled synthesis of yttrium gallium garnet spherical nanostructures modified by silver oxide nanoparticles for enhanced photocatalytic properties

Spherical yttrium gallium garnet (Y3Ga5O12) samples were prepared by a single-step hydrothermal synthesis method, and these particles were coated with silver oxide (Ag2O) nanoparticles by following a facile wet chemical approach at ambient temperature. The structural, morphological, vibrational and optical properties of the as-prepared and Ag2O modified Y3Ga5O12 samples were analyzed. From Rietveld refinement of X-ray diffraction patterns, the crystal structure of the Y3Ga5O12 sample was refined. The morphological properties confirmed that the particles were spherical and their surfaces were covered with Ag2O nanoparticles. The Ag2O modified Y3Ga5O12 sample exhibited a relatively enhanced photocatalytic activity compared to the pure Y3Ga5O12 sample in Rhodamine B solution, suggesting that the introduction of Ag2O broadens the absorption of light and controls the photogenerated carrier recombination in Y3Ga5O12. These results provide a clear perspective on the synthesis of hybrid photocatalyst materials which have several ways of photogenerated carrier migration.

Ambient and high pressure spectroscopy of Ce^3+ doped yttrium gallium garnet

Low temperature infrared absorption in the region of intra–shell 4f-4f transitions of Ce3+ ions in bulk yttrium gallium garnet crystals reveals existence of different Ce3+ centers. In addition to the major center, related to Ce substituting yttrium, at least two other centers exist, most probably attributed to the rare-earth antisites, i.e. rare-earth ions at the Ga crystallographic positions. Temperature dependence of the visible absorption related to the 4f-5d transitions shows influence of thermal population of the second higher-lying level of the 2F5/2 ground state, located 159 cm−1 above the lowest level. 5d→4f luminescence of Ce3+ is observed at elevated pressure and shows signatures of pressure-induced crossing of the lowest 5d state of Ce3+ with the conduction band states.

New perspective in garnet phosphor: low temperature synthesis, nanostructures, and observation of multimodal luminescence.

Herein, we report a new concept for garnet materials in terms of the synthesis of nanocrystalline structure at low temperatures and its multimodal luminescence processes. Terbium- and ytterbium-ion-codoped yttrium gallium garnet nanophosphors have been synthesized via solution combustion technique; nearly pure phase nanophosphor samples were obtained. The synthesized nanophosphor shows efficient multimodal upconversion (UC), downshifting (DS), and quantum cutting (QC)/downconversion (DC) luminescence, which is a new paradigm in garnet material. The garnet nanophosphor shows strong green emission through DS and UC processes both. Furthermore, cooperative energy transfer (CET) has been described in detail, and a possible mechanism for the QC process is also proposed. A UV/blue photon absorbed by Tb(3+) ion splits into two near-infrared photons (wavelength range 900-1040 nm), emitted by a Yb(3+) ion pair, with an efficiency of more than 100%. The Yb(3+) concentration dependent ET from Tb(3+) to Yb(3+) has been verified using time domain analysis. An ET efficiency as high as 28% and a corresponding QC efficiency of about 128% (for 15 mol % of Yb(3+) concentration) have been attained. Such a multimode emitting nanophosphor could be very useful in display devices and for enhancing the conversion efficiency of next generation solar cells via spectral modification etc.

Some interesting features of the Tb3+ magnetooptics in the paramagnetic garnets

The spectra of the absorption, luminescence, magnetic circular dichroism (MCD) and magnetic circular polarization of luminescence (MCPL) in the terbium–yttrium gallium garnet Tb3+:Y3Ga5O12 (Tb:YGG) have been studied within the visible and near ultraviolet (UV) spectral range for temperatures T=85 and 300K. The MCD spectrum observed within the UV absorption band for Tb:YGG is associated with spin- and parity-allowed electric-dipole 4f→5d transitions occurring between levels of the ground 7F6 multiplet and the 7D state of the excited 4f(7)5d configuration of the Tb3+ ion. Analysis of the spectral and the temperature dependences of the magnetooptical and optical spectra has made it possible to identify magneto-optically-active 4f→4f transitions occurring between Stark sublevels of the 5D4 and 7F5 multiplets in Tb3+:YGG. Quantum mechanical “mixing” of the three lowest energy Stark singlets in the excited 5D4 multiplet by an external magnetic field H leads to the change of the circularly polarized luminescence line intensities. The Zeeman effect in the UV absorption band 7F6→5L10 of Tb3+:YGG at T=85K was also studied. The magnetic field dependence of the Zeeman splitting of some absorption lines is found to exhibit unusual behavior: as the magnetic field increases, the band splitting decreases rather than increases. A parameterized Hamiltonian defined to operate within the entire 4f(8) ground electronic configuration of Tb3+ was used to model the experimental Stark levels, their irreducible representations (irreps.) and wave functions. The crystal-field parameters were determined using a Monte-Carlo method in which nine independent crystal-field parameters, were given random initial values and optimized using standard least-squares fitting between calculated and experimental levels. The final fitting standard deviation between 101 calculated and experimental Stark levels is 16.7cm−1.

Efficient eye-safe neodymium doped composite yttrium gallium garnet crystal laser

We report a laser-diode pumped continuous-wave (cw) and passively Q-switched eye-safe laser at about 1.42μm with the neodymium-doped yttrium gallium garnet (Nd:YGG) crystal for the first time to our knowledge. The composite Nd:YGG crystal was developed originally. A systematic comparison of laser performance between the homogeneously doped and composite Nd:YGG crystal was made, which showed that the composite Nd:YGG manifested less thermally induced effects. Cw output power of 2.06W was obtained with the slope efficiency of 20.7%. With a V:YAG as a saturable absorber, the passive Q-switching at 1.42μm was gotten with the pulse width, pulse energy, and peak power of 34ns, 46.7μJ, and 1.4kW, respectively. The present work should provide a potential candidate for the generation of eye-safe lasers.

Analysis of thermal effects in end-diode-pumped, Q-switched Nd:YVO4 laser

We present a laboratory model of a Q-switched Nd:YVO 4 laser with thermal effects compensation dedicated as a laser head for marking devices. Theoretical analysis on thermal effects were performed and resonator parameters were optimized. For 10 kHz repetition rate we obtained about 0.25 mJ of pulse energy corresponding to about 45 kW of peak power with slope efficiency 14%. M 2 parameter was 1.6. Full Text: PDF References J. E. Geusic, H. M. Marcos, L. G. Van Uitert, "Laser oscillations in nd-doped yttrium aluminum, yttrium gallium and gadolinium garnets", Applied Physics Letters 4 (10), (1964) CrossRef L. Gorajek, L. Galecki, "Tunable, gain switched Ti3+:Al2O3 laser pumped by intracavity frequency doubled Nd3+:YLF laser", Photonics Letters of Poland 1, No 3, 136-138 (2009) CrossRef W. Zendzian, J. K. Jabczynski, P. Wachulak, J. Kwiatkowski, "High-repetition-rate, intracavity-pumped KTP OPO at 1572 nm", Appl. Phys. B 80, 329-332 (2005) CrossRef J. Swiderski, A. Zajac, P. Konieczny, M. Skorczakowski, "Numerical model of a Q-switched double-clad fiber laser", Opt. Express 12, 3554-3559 (2004) CrossRef J. Swiderski, A. Zajac, P. Konieczny, M. Skorczakowski, "Q-switched Nd-doped double-clad fiber laser", Opto-Electronics Review, vol. 13, no. 3, 29-33, 2005 DirectLink

Electronic and elastic properties of yttrium gallium garnet under pressure from ab initio studies

In this paper, we present an ab initio study within the framework of density functional theory employing the generalized gradient approximation applied to the study of the structural, elastic, and electronic properties of yttrium gallium garnet, Y3Ga5O12, under hydrostatic pressure. The calculated structural ground state properties are in good agreement with the available experimental data. Pressure dependence of the elastic constants and the mechanical stability are analysed up to 90 GPa, showing that the garnet is mechanically unstable above 84 GPa. We also present the electronic band structure calculations which show that upon compression the fundamental direct gap first increases up to 63 GPa and later monotonically decreases under pressure.

Improved optical properties in nanocrystalline Ce:YGG garnets via normal and reverse strike co-precipitation method

There is a difference in the growth of nanoparticles based on the environment in which nucleation occurs as is observed by changing the order of reactant being added to the precipitant present in excess called the normal strike and reverse strike method. The effect of particle size on optical properties of Ce:YGG (Ce doped yttrium gallium garnet) obtained via normal and reverse strike synthesis has been investigated. The normal strike route led to smaller particle size, good chemical homogeneity as well as significant improvement in photoluminescence properties compared to the reverse strike route. A comparative study of Ce:YGG nanoparticles, synthesized via the two different methods and their optical properties are discussed. There is an enhancement in the photoluminescence efficiency in nanoparticles obtained by the normal strike method mainly due to homogeneous distribution of active ions in the host which is essential to avoid quenching.

Weak Crystal Field in Yttrium Gallium Garnet (YGG) Submicrocrystals Doped with Cr3+

Yttrium gallium garnet (YGG) submicrocrystals having 80 nm average diameters doped with Cr3+ (0.1–40%) were synthesized by the citrate method. Pure cubic garnets were obtained in wide range (0.1–15%) of dopant concentration. Chromium ions replace Ga3+ at the octahedral sites and experience an intermediate or weak crystal field, depending only on Cr3+ concentration. The weak crystal field is observed when the dopant concentration exceeds 3%. The origin of such behavior is discussed.

555 nm laser sources based on intracavity frequency doubling of Nd:YGG laser

We report for the first time a yellow-green laser at 555 nm generation by intracavity frequency doubling of a continuous wave (CW) laser operation of a 1110 nm Nd-doped yttrium gallium garnet (Nd:YGG) laser under in-band diode pumping at 808 nm. An LBO crystal, cut for critical type I phase matching is used for second harmonic generation of the laser. At an incident pump power of 18.5 W, as high as 2.31 W of CW output power at 555 nm is achieved. The optical-to-optical conversion efficiency is up to 12.4%, and the fluctuation of the yellow-green output power was better than 2.8% in the given 4 h.

Diode-pumped Nd:YGG continuous-wave laser at 1.33 μm

We demonstrated a laser-diode pumped Nd-doped yttrium gallium garnet (Nd:YGG) crystal continuous wave (CW) laser at 1.33 μm for the first time to our knowledge. At an incident pump power of 18.5 W, as high as 3.09 W of CW output power at 1.33 μm is achieved. The slope efficiency with respect to the incident pump power was 21.3%, and the fluctuation of the output power was better than 2.8% in the given 4 h. The beam quality factor M2 is 1.14 and 1.16 for tangential direction and sagittal direction, respectively.