YGG Crystal Research Articles

Growth, spectroscopy and laser operation of in-band pumped Ho3+-doped Yttrium Gallium Garnet

We report on the crystal growth of a 2.86 at.% Ho:YGG crystal, its structural and spectroscopic characterization, as well as on its first laser operation near 2.1 µm under in-band pumping by a Tm-fiber laser.

Optical properties and surface blistering visualization on multiple-energy He-implanted Yb:YGG crystal by annealing treatment

In this work, multiple-energy (400 keV, 450 keV, 500 keV) He ions implantation is proposed on Ytterbium doped YGG crystal. The choice of multiple-energy could widen the barrier layer by He ions accumulation at the end of the trajectory. Prism coupling and end-face coupling are used to obtain the optical properties in the waveguide region. The damage displacement profile and energy loss profile are simulated by SRIM 2010. The comparison between substrate and waveguide region on the micro-luminescence properties and Raman characteristics of Yb:YGG crystal are investigated also. The sequence annealing treatment results indicate that the sample surface break to pieces when the annealing temperature up to 600 °C, which provide direct evidence for the formation of He-bubble in He-implanted Yb:YGG crystal. Therefore, the results of this work provide reference value on YGG film fabrication by using multiple-energy He ion implantation.

Refractive index enhanced well-type waveguide in Nd:YGG crystal fabricated by swift Kr8+-ion irradiation

In this work, we introduced a Nd:YGG single mode planar waveguide fabricated by swift heavy ion irradiation. The initial Kr8+ ions beam energy was 2.1 GeV, after passing through the Al foil the beam energy came to 30 MeV. The implantation fluence was 2×1012 ions/cm2. A well region with the refractive index increment in near the surface was obtained after ion irradiation. This index increment was attributed to the ion-induced electronic damage. The characterization of the optical planar waveguide in Nd:YGG crystal was tested by prism coupling and end face coupling method. The micro-luminescence and Raman properties of our ion-irradiation Nd:YGG crystal were investigated. This work has reference value for integrated optical devices on Nd:YGG crystal.

The formation and optical properties of planar waveguide in laser crystal Nd:YGG by carbon ion implantation

As one kind of prominent laser crystal, Nd:Y3Ga5O12 (Nd:YGG) crystal has outstanding performance on laser excitation at multi-wavelength which have shown promising applications in optical communication field. In addition, Nd:YGG crystal has potential applications in medical field due to its ability of emit the laser at 1110nm. Optical waveguide structure with high quality could improve the efficiency of laser emission. In this work, we fabricated the optical planar waveguide on Nd:YGG crystal by medium mass ion implantation which was convinced an effective method to realize a waveguide structure with superior optical properties. The sample is implanted by C ions at energy of 5.0MeV with the fluence of 1×1015ions/cm2. We researched the optical propagation properties in the Nd:YGG waveguide by end-face coupling and prism coupling method. The Nd ions fluorescent properties are obtained by a confocal micro-luminescence measurement. The fluorescent properties of Nd ions obtained good reservation after C ion implantation. Our work has reference value for the application of Nd:YGG crystal in the field of optical communication.

Third-order nonlinearity and passive Q-switching of Cr⁴⁺:YGG garnet crystal.

We demonstrate the third-order nonlinear optical properties of Cr(4+):Y(3)Ga(5)O(12) (Cr(4+):YGG) and Q-switched lasers with Cr(4+):YGG as the saturable absorber for the first time to our knowledge. The third-order nonlinear properties, including the optical Kerr nonlinearity and saturable absorption, were systematically measured and analyzed in detail by using a Z-scan technique. The measured data show that Cr(4+):YGG has a large nonlinear refractive index, ground-state absorption cross section, and excited-state absorption cross section in contrast to Cr(4+):Y(3)Al(5)O(12) (Cr(4+):YAG). With a Nd:YGG crystal as the gain medium and a Cr(4+):YGG crystal as the saturable absorber, the passively Q-switched laser was performed. The shortest pulse width and largest pulse energy were achieved at the absorbed pump power of 8 W with the values of 9.1 ns and 26.1 μJ, respectively, corresponding to the average output power of 0.87 W and peak power of 2.9 kW. The results indicate that Cr(4+):YGG is an available and promising optical switcher for pulsed lasers.

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.

Planar Nd:YGG waveguide fabrication by multiple energy He ion implantation

Rare-earth garnet single-crystals are promising candidates for optical applications. Previous reports showed that they have controllability and good reservation of Nd ions fluorescent properties in the ion implanted waveguide. Thus, we studied the optical and fluorescent properties of the Nd:YGG waveguide structure formed by multi-energy He ion implantation. The fabrication and characterization of the optical planar waveguide in Nd:YGG crystal by using multi-energy He ion implantation was presented. The thermal stability of our ion-implanted Nd:YGG crystal was investigated. The guided-mode and annealing properties at the wavelength of 633nm were investigated through prism-coupling and end-face coupling measurements, and the fluorescent properties were investigated by a confocal micro-luminescence experiment. This work could supply an operation reference for integrated optical devices.

Development of a single crystal with a high index of refraction

Time-of-flight Positron emission tomography (TOF-PET) is one of the next-generation medical imaging methods, which requires scintillators with a very short decay time. However, the shortest scintillation decay times are typically 20–30ns, and these values are not sufficient for TOF-PET. Cherenkov counters are used in high energy physics and they are expected to be applied in medical imaging due to their short decay time. Here, high-refractive index materials are necessary for Cherenkov radiators to reach a high light output. We measured refractive indices of Gd3Ga5O12 (GGG), Y3Ga5O12 (YGG) and Lu3Ga5O12 (LuGG) crystals grown by a micro-pulling-down (μ-PD) method. The GGG, YGG and LuGG crystals were found to have refractive indices of ~2.5, ~2.3 and ~2.3 at 400nm, respectively. Then we grew a 40mm diameter GGG crystal by the Czochralski method, and the emission decay times of the GGG crystals irradiated with muons and gamma rays were 10±1ns and 10±2ns, respectively, using a photomultiplier tube (Hamamatsu R6231-100). Cherenkov light of the GGG crystal could be observed for the gamma-ray irradiation.

Characteristics of Nd:YGG Laser Operating at 4F3/2–4I9/2

The laser properties of the Nd:YGG crystal are investigated. The absorption spectrum from 500 to 900 nm and emission spectrum from 850 to 1400nm of Nd:YGG are measured. As much as 1.35 W output power of fundamental laser operating at 935 and 938 nm with a slope efficiency of 15.7% and 105 mW output power of frequency doubled blue laser are successfully obtained.

Spin Hamiltonian parameters and structural disorder analysis for Cr 3+ ion in YGG crystals

A new crystalline lattice distortion model has been proposed, on the basis of it, the relations between spin Hamiltonian parameters and crystal micro structure have been established. By taking into account slight magnetic interactions, including spin–spin (SS), spin-other-orbit (SOO), and orbit–orbit (OO) interactions, the local structure of Cr 3+ ion in YGG crystal has been studied using complete diagonalization method (CDM). The studies show that the local structure in the YGG:Cr 3+ crystal is of the compressed trigonal distortion. The ligand oxygen plane moved 0.0138 nm toward Cr 3+ ion along C 3-axis. Accordingly, the SH parameters in YGG:Cr 3+ crystal are explained successfully.

Complex oxides: Electron excitations and their relaxation

The luminescence excitation spectra and the electron excitation relaxation features of Al 2O 3, YAP, YAG, and YGG crystals are discussed from the viewpoint of the specificity caused by the complexity of the unit cell. The branching of relaxation is observed between the usual channel, characteristic of the simple wide-band insulators, and the one connected with the nonbonding states appearing in complex oxides. A model describing such branching is proposed. For comparison, the luminescent features of a CaWO 4 crystal containing clearly separable oxyanion structures (in contrast to the crystals mentioned) are studied.

A study of the stress dependence of zero-field splitting for YGG: Mn 2+ crystal

The stress dependence of zero-field splitting for Mn 2+ ion in trigonal site of YGG crystal has been reasonably explained by calculating the spin-lattice coupling coefficients G 44 within the framework of cubic symmetry approximation. On this basis, the zero-field splittings for Mn 2+ ion in the trigonal site of YGG and YAG crystals can also be interpreted in terms of the distinctive trigonal distortions.