Gallium Garnet Research Articles

Temperature controlled magnon–photon coupling in a YIG/GGG-superconducting cavity coupled system

To explore potential applications in classical and quantum information transfer, the hybrid systems between yttrium iron garnet (YIG) and cavities have been extensively studied, and four coupling regimes have been defined based on the relative strength between the coupling strength and dissipation rate of each subsystem. Achieving the control of magnon–photon coupling between nano-thick YIG films and cavities remains to be explored. We experimentally measure the microwave transmission spectra of a nano-thick yttrium iron garnet/gadolinium gallium garnet (YIG/GGG) film coupled to a superconducting cavity at different temperatures. The dissipation rate of the superconducting cavity increases significantly with decreasing temperature, which is influenced by the temperature-dependent magnetic susceptibility of the GGG substrate. Accompanied by the temperature-dependent magnon dissipation rate, a continuous transformation of the coupled system in strong coupling, Purcell and weak coupling regimes is achieved.

A Compact and Low-Loss Tunable Bandpass Filter Using YIG/GGG Film Structures

A compact and low-loss magnetically tunable bandpass filter (BPF) is presented in this letter. The yttrium iron garnet/gadolinium gallium garnet (YIG/GGG) film structure is regarded as a resonator excited by a stepped terminal short-circuited stripline, and additional metal rings are plated on the other side of the RO4350 substrate. Two YIG/GGG film structures placed in parallel are directly coupled. This structure enhances the RF magnetic field, reduces filter loss, and suppresses parasitic response. The filter design and geometrical parameter optimization are first carried out using CST Studio Suite. When the magnetic field changes from 1820 to 7420 Oe, the filter is tuned from 5 to 19 GHz, with a 3-dB bandwidth (BW) of 62–107 MHz, insertion loss (IL) of less than 2 dB, and parasitic response suppression of about 20 dB over the entire tuning range (TR).

Micro-CT evaluation of the removal of root fillings using rotary and reciprocating systems supplemented by XP-Endo Finisher, the Self-Adjusting File, or Er,Cr:YSGG laser.

This study aimed to compare the effectiveness of a single-file reciprocating system (WaveOne Gold, WOG) and a multi-file rotary system (ProTaper Universal Retreatment, PTUR) in removing canal filling from severely curved canals and to evaluate the possible adjunctive effects of XP-Endo Finisher (XPF), the Self-Adjusting File (SAF), and an erbium, chromium: yttrium, scandium, gallium garnet (Er,Cr:YSGG) laser using micro-computed tomography (μCT). Sixty-six curved mandibular molars were divided into 2 groups based on the retreatment technique and then into 3 based on the supplementary method. The residual filling volumes and root canals were evaluated with μCT before and after retreatment, and after the supplementary steps. The data were statistically analyzed with the t-test, Mann-Whitney U test, analysis of covariance, and factorial analysis of variance (p < 0.05). PTUR and WOG showed no significant difference in removing filling materials (p > 0.05). The supplementary techniques were significantly more effective than reciprocating or rotary systems only (p < 0.01). The supplementary steps showed no significant differences in canal filling removal effectiveness (p > 0.05), but XPF showed less dentin reduction than the SAF and Er,Cr:YSGG laser (p < 0.01). The supplementary methods significantly decreased the volume of residual filling materials. XPF caused minimal changes in root canal volume and might be preferred for retreatment in curved root canals. Supplementary approaches after retreatment procedures may improve root canal cleanliness.

A Comparision of conventional and laser assisted desensitization techniques for treating dentinal hypersensitivity.

The study's objective was to assess the effectiveness of conventional and laser-assisted desensitization in treating dentinal hypersensitivity (DH). Twenty patients were divided into experimental and control groups. Following scaling, patients in the control group were instructed to utilize desensitization paste; however, after comprehensive scaling, patients in the experimental group received treatment with the erbium, chromium, yttrium, scandium, gallium garnet (Er, Cr: YSGG) laser. Before laser emission, the visual analog scale (VAS) score was obtained for both groups. Postoperative VAS scores were recorded right away, 1 week and 1 month later for the test group, and 1 week and 1 month later for the control group, following the use of desensitizing paste. In comparison to the control group, the Er, Cr: YSGG laser treatment had a substantially higher desensitizing impact right away, according to the data. The variances in the mean VAS scores between baseline and all time periods after treatment for the test group were statistically significant. At any subsequent assessment, there were no discernible variations in plaque index between the test and control groups. The Er, Cr: YSGG laser is found to be more effective than the control group in treating DH within the confines of this investigation.

Evaluation and study of spin Seebeck effect in Pt/Y3Fe5O12/Gd3Ga5O12 and Pt/Y3Fe5O12/sapphire systems

Utilization of the spin Seebeck effect, a method for obtaining clean natural energy, is attracting more and more attention. We investigated the spin Seebeck voltage in relation to the saturation magnetization in yttrium iron garnet (YIG). We found that it is not proportional to saturation magnetization in YIG, indicating the existence of spin-current conductance in YIG. Pt/YIG samples with the same interface roughness and different structures exhibited different spin Seebeck voltages. The difference in the minimum YIG thicknesses for the saturation of the spin Seebeck voltage of Pt/YIG/gadolinium gallium garnet and Pt/YIG/sapphire structures was estimated on the basis of the relationship between the proportionality constant and the thickness dependence. The crystallinity of the YIG on these two substrates was investigated by X-ray diffraction spectrum observation. The spin-current conductance in Pt/YIG/substrates was found to be affected by the crystallinity of the YIG films.

Ytterbium-doped-garnet crystal waveguide lasers grown by pulsed laser deposition

The growth of a range of crystal garnets by pulsed laser deposition is presented. As a result of optimization of the fabrication process, films can now be grown with optical quality approaching that of bulk material. To demonstrate this, we present laser performance from a Yb:YAG film with 70% slope efficiency and >16 W of output power. In addition, we present the first pulsed laser deposition of laser quality Yb:GGG and Yb:YGG. Watt-level laser performance is achieved for these two gallium garnets and routes to further performance improvements and potential applications of these films are discussed.

Heat capacity of rare-earth cuprates, orthovanadates, and aluminum garnets, gallium garnets, and iron garnets

The correlation between the heat capacities of rare-earth cuprates, orthovanadates, and garnets with ionic radius R3+ has been analyzed. It has been shown that the values of Cp0 change consistently depending on the radius R3+ within the corresponding tetrads (La-Nd, Pm-Gd, Gd-Ho, Eu-Lu).

Luminescent Magneto-Optical Photonic Crystals

We compare luminescent properties of several Er-doped garnet films as building blocks in all-garnet heteroepitaxial magneto-optical photonic crystals: La3Ga5O12, Gd3Ga5O12, Y3Fe5O12, Bi3Fe5O12, and Bi2.97Er0.03Fe4Al0.5Ga0.5O12. Er substituents on the dodecahedral lattice sites do not decrease giant Faraday rotation in Bi3Fe5O12 garnet; meanwhile providing intense room temperature C-band photoluminescence (PL). Fe3+ ion works as a sensitizer for Er resulting in fivefold PL enhancement in iron garnets compared to gallium ones. PL lifetime in gallium garnets is in millisecond range reaching 6 ms in Gd2.9Er0.1Ga5O12. The first luminescent one-dimensional heteroepitaxial all-garnet magneto-optical (MO) photonic crystal was composed from diamagnetic Sm3Ga5O12 and MO-active Bi2.97Er0.03Al0.5Ga0.5O12 garnet layers by rf-magnetron sputtering on Gd3Ga5O12(111) substrate. Substitution of ferric ions by aluminum and gallium improved transparency and induced perpendicular anisotropy in pure Bi3Fe5O12. Photonic crystals owned a record high magneto-optical quality and a latching type (magnetic remnant) Faraday rotation (FR). At the resonance wavelength 775 nm, specific FR θF = − 14.1 deg/μm and MO-quality factor Q = 99.3 deg represent the highest MO performance achieved so far. Long-lived near-IR luminescence in Er substituted gallium and iron garnet layers used both as Bragg mirrors and microcavities promises magneto-optical photonic crystals to become an active lasing medium.

Interaction of Er3+ ions in Er-doped calcium — niobium — gallium garnet crystals

The processes of nonradiative energy transfer in calcium — niobium — gallium garnet (CNGG) crystals doped with Er3+ ions are studied. It is found that the energy of erbium ions in the Er:CNGG crystal with the erbium atomic concentrations CEr=6% and 11% is transferred via the nonradiative co-operative processes 4I11/2→ 4I15/2, 4I11/2→ 4F7/2, 4I11/2→ 4I15/2, 4I13/2→ 4F9/2; and 4I13/2→ 4I15/2, 4I13/2→ 4I9/2, whose efficiency increases with increasing intensity of exciting radiation. It is shown that the cross-relaxation processes 4S3/2→4I9/2, 4I15/2→4I13/2, whose intensity depends on the concentration of Er3+ ions, are characteristic for Er:CNGG crystals with the Er atomic concentration above 1%.

A Tunable X-Band Band-Pass Filter Module Using YIG/GGG Layer on RT/Duroid Substrate

A tunable X-band band-pass filter (BPF) module that consists of an 8-12-GHz passive BPF and a pair of tunable band-stop filters (BSFs) using yttrium iron garnet/gadolinium gallium garnet (YIG/GGG) layers on RT/Duroid substrate is reported. The passive BPF and the tunable BSFs were first designed, simulated, and optimized using AWR Microwave Office Simulator. The tunable X-band BPF module was then constructed and simulated under 2-D bias magnetic fields with Ansoft HFSS software suite. The measured passband of the passive BPF was 7.8-11.8 GHz, with the center frequency at 9.8 GHz and the 3-dB bandwidth of 4.8 GHz. With the sets of bias magnetic fields at 1,700 and 2,360 Oe; 2,570 and 3,180 Oe; and 1,725 and 3,180 Oe applied on the pair of BSFs, tuning for the passband of the BPF module toward the high end, the low end, and the center was accomplished with the center frequency at 11.5, 7.9 and 9.8 GHz, the 3-dB bandwidths of 1.0, 1.1, and 1.2 GHz, and the tuning ranges of 3.4, 4.0, and 3.6 GHz, respectively. A good agreement between the simulation and experimental results was achieved.

Highly luminescent garnets for magneto-optical photonic crystals

We compare luminescent properties of several Er-doped garnets as building blocks in all-garnet heteroepitaxial magneto-optical photonic crystals. Pulsed laser deposited La3Ga5O12, Gd3Ga5O12, Y3Fe5O12, and rf-magnetron sputtered Bi3Fe5O12 were chosen to host Er3+ ions on dodecahedral lattice sites. Er substituents with the concentration of 0.5 at. % (0.1 garnet formula units) do not decrease giant Faraday rotation in Bi2.9Er0.1Fe5O12 garnet; meanwhile providing intense room temperature C-band photoluminescence (PL). Fe3+ ion works as a sensitizer for Er resulting in fivefold PL enhancement in iron garnets compared to gallium ones. PL lifetime in gallium garnets is in millisecond range reaching almost 6 ms in Gd2.9Er0.1Ga5O12. We conclude Er substitution in gallium and iron garnet layers used both as Bragg mirrors and microcavities promises magneto-optical photonic crystals to become an active lasing medium.

Evaluation of the parameters of cation distribution in Y3A5−z B z O12 solid solutions

Crystal chemical models are proposed for describing the regularities in the distributions of ions and point defects in solid solutions of yttrium aluminum, yttrium gallium, and yttrium iron garnets. The concentration dependences of the distributions of ions and point defects in solid solutions are evaluated in terms of multidimensional nonlinear optimization.

Charge-transfer luminescence and spectroscopic properties of Yb 3+ in aluminium and gallium garnets

Luminescence of Yb 3+ from the charge-transfer state with broad emission bands and short radiative lifetimes (few to tens of nanoseconds depending on the host lattice and the temperature) is attractive for the development of fast scintillators capable of discriminating very short events. The most important currently considered application is that in solar neutrino ( ν e) real-time spectroscopy, since the ν e capture by 176Yb is followed by a specific emission signature which can accordingly excite the Yb 3+ fluorescence. Studies on scintillation and luminescence in aluminium garnets containing Yb 3+ have shown that these materials meet some of the required properties for such scintillators. In defining our priorities, the best compromise between host crystal, Yb 3+ concentration, production method, post-growth treatment and performance is to be considered based on the studies of charge-transfer luminescence and quenching mechanisms. The experiments have been extended to a large number of compounds: YAG:Yb–YbAG, YGG:Yb–YbGG, YAP:Yb–YbAP, LaYbO 3 in the form of single crystals and/or powders. In garnets, the temperature-dependent fluorescence intensity and decay time under X-ray and VUV excitations decrease at low temperatures ( T<100 K) and demonstrate the important role played by the traps. The thermoluminescence peaks show a strong dependence on the crystal history, composition and impurities introduced intentionally. The fluorescence intensity and decay time are also dependent on Yb 3+ concentration and the presence of Yb 2+. The results trace the major directions to optimised scintillators in terms of their efficiency and lifetime.

Systematics of 4f electron energies relative to host bands by resonant photoemission of rare earth doped optical materials

Relative energies of 4f n electronic states and crystal band states are important for a fundamental understanding of rare-earth-doped optical materials and a practical understanding of each material's potential performance in specific applications. With this motivation, the 4f n ground state binding energies of rare earth ions have been studied in the gallium garnets using resonant photoemission spectroscopy and compared with the aluminum and iron garnets. The 4d–4f photoemission resonance was used to separate and identify the 4f n and valence band components of the spectra, and theoretical 4f photoemission spectra were fit to experimental results to accurately determine electron binding energies. A two-parameter empirical model was used to successfully describe the relative energies of the 4f n ground states in these materials. The success of this empirical model indicates that measurements on as few as two different rare earth ions in a host are sufficient to predict the energies of all rare earth ions in that host. This analysis shows that systematic shifts in the relative energies of 4f n states and crystal band states between different garnets arise entirely from shifts of the band states, while each rare earth ion maintains the same absolute binding energy for all garnets studied. These results suggest that further studies of additional host compounds using both photoemission and optical spectroscopy will rapidly lead to a broader picture of the host crystal's effect on 4f electron binding energies.

Time resolved spectroscopy of laser output of Nd 3+ doped calcium, niobium, gallium garnet

Stimulated emission experiments in the 4 F 3 2 → 4 I 11 2 transition of Nd 3+ in Ca 3(GaNb) 3O 12 show that two laser lines are emitted simultaneously and both independently. These experiments show the behaviour of the laser emission from two distinguishable subsets of Nd 3+ sites. This behaviour has been modeled using a four-level spectral rate-equation laser model, assuming the existence of two kinds of Nd 3+ populations with different emission spectra and a homogeneous line broadening at each site. The model explains the measured laser spectrum as well as the time delay between the emission of both laser lines.

Spectral-domain analysis of dispersion characteristics of open coupled microstrip lines on YIG/GGG structures

This paper is to study coupled microstrip lines on layered yttrium iron garnet/gadolinium gallium garnet (YIG/GGG) structures. The problem is formulated using the spectral-domain technique, and the spectral Galerkin's method is utilized to compute the dispersion characteristics. Numerical results are presented for various values of structural and physical parameters such as widths of strips, thicknesses of YIG and GGG, separation between the strips, and applied DC magnetic field.

Femtosecond solid-state lasers using Nd^3+-doped mixed scandium garnets

The mode-locking features of a series of Nd3+-doped solid solutions of aluminum and gallium garnets are investigated, and the influence of multiline gain spectra on mode-locking performance is discussed. With an additive-pulse nonlinear Michelson interferometer used to mode lock the laser passively, pulses as short as 260 fs are obtained. The effect of interferometer detuning on the pulse characteristics is studied.

Deformation of single crystal sheets with a heterogeneous chemical composition

,Deformation of single crystal sheets, used as substrates for epitaxial structures, reduces the yield of suitable products [1]. In this work, we examine low-dislocation single crystal sheets which are deformed mainly as a result of the presence of point-type defects in their volume. This type of defect can be caused both by chemical heterogeneity of the composition in respect of the main components of the solid solution of the compound in its homogeneity region as well as by the nonuniform distribution of impurities in the volume of the single crystal. Analysis of deformation was carried out in the dimensionless forms so that the results can be used for a wide range of materials with the examined type of structural heterogeneity. Calculations were also carried out for typical parameters of the structure of the specific material, i.e,, gadolinium---gallium garnet.

Ultrashort pulses of stimulated emission by Nd3+-doped (4F3/2 →4I11/2 channel) anisotropic fluorides, acentric dispersed silicates, and gallium garnets

Etude des impulsions breves (picoseconde) d'emission stimulee ― dans le regime du mode-locking passif, a 300 K. Emission stimulee obtenue par pompage optique. Mesure de la duree des impulsions breves par une camera electro-optique. Distribution energetique des impulsions etudiee par un analyseur a multicanaux. Description detaillee de l'appareillage. Resultats

Spectral and luminescence properties of Cr^3+ and Nd^3+ ions in gallium garnet crystals

The effective peak stimulated-emission cross section of chromium-doped gadolinium–scandium–gallium garnets (GSGG) has been determined to be 8.5 × 10−21 cm2 at room temperature. The values of the energy-gap ΔE(2E − 4T2) chromium fluorescence lifetime and the chromium → neodymium energy-transfer parameter CDA(Cr–Nd) are determined for several gallium garnets. Temperature-dependent absorption and luminescence spectra of neodymium-doped GGG and GSGG are reported and discussed in the context of their use as laser materials.