YAG Crystal Research Articles

Influence of Cr3+ doping on the spectroscopies and laser performance of Cr,Nd:YAG crystal operated at 1.06 μm

We present a high-quality Cr,Nd:YAG crystal with 1.0 at. % Cr3 + and 1.1 at. % Nd3 + grown successfully by the Czochralski method. Spectroscopy results indicate that codoped Cr3 + ions are advantageous for improving pumping efficiency. The maximum average power of 20.24 W operated at 40 Hz and 1.06 μm is obtained on the Cr,Nd:YAG crystal, with electrical-to-optical and slope efficiencies that correspond to 3.00% and 3.77%. Meanwhile, the maximum average power of only 13.32 W is obtained on the Nd:YAG crystal, with the electrical-to-optical and slope efficiencies of 1.97% and 2.47%, respectively. In addition, the laser beam quality of the Cr,Nd:YAG crystal is comparative with that of the Nd:YAG crystal. Therefore, the Cr,Nd:YAG is a promising laser crystal with higher laser performance and stronger radiation-resistant ability than the Nd:YAG crystal. Thus, the Cr,Nd:YAG crystal can be applied to high-power systems and radiant environments.

Amplification of higher order Poincaré sphere beams through Nd:YLF and Nd:YAG crystals

Scalar and vector orbital angular momentum modes, generally described by the higher order Poincare sphere (HOPS), have found many applications to date, but limited to low-power levels. It has thus become topical to consider amplification of such structured light modes. Here, we employ recently developed characterisation tools for HOPS beams to study their purity through birefringent and non-birefringent amplifiers in a master oscillator power amplifier configuration. We outline a general theory for the problem that considers both vector and gain perspectives, and confirm the theory by experiment.

All-fiber-integrated Yb:YAG-derived silica fiber laser generating 6 W output power.

A Yb:YAG-derived silica fiber was fabricated by a molten-core fabrication method, in which a Yb:YAG crystal was used as the core material and a silica tube was used as the cladding material. The fiber's transmission loss was measured to be 0.49 dB/m at 1.55 µm, using a cut-back method. The fiber microstructure image showed that the cladding region was a uniform glass structure, while the core structure was amorphous. An all-fiber-integrated cladding-pumped laser based on Yb:YAG-derived silica fiber was demonstrated. With an incident pump power of 28 W, an output power of 6 W was obtained at 1.06 μm, with a slope efficiency of 21.7%.

A novel solid-solution garnet Yb:YAG-MnASG with enhanced spectral properties

A novel solid-solution garnet Yb3+ doped Y3Al5O12Mn3Al2(SiO4)3 (Yb:YAG-MnASG) has been designed and grown for the first time. The polycrystalline materials, crystal growth, crystal structures, absorption and emission spectra, energy level schema, fluorescence lifetime and laser performance parameters were investigated in detail. Owing to the inhomogeneity in the local environment of Yb3+ caused by the cationic substitutions of Mn2+ for Y3+, Si4+ for Al3+ and high crystal-field strengths caused by distorted host sites, both of the absorption and emission spectral bandwidth of Yb:YAG-MnASG crystal are broadened compared with Yb:YAG. The maximal full width at half maximum (FWHM) of absorption spectra around 940 nm and emission spectra around 1030 nm for Yb:YAG-MnASG crystal are almost 1.2 and 2.5 times larger than those of Yb:YAG crystal, respectively. The results reveal that the novel solid-solution garnet Yb:YAG-MnASG is an excellent candidate for ultrafast pulse laser crystal.

An efficient 1052 nm Nd:LaMgB5O10 laser: a promising master oscillator for Nd:glass amplifiers

The laser operation of a new neodymium-doped pentaborate crystal, Nd:LaMgB5O10, lasing at 1052 nm wavelength was demonstrated. With 14.76 W absorbed power of diode-pumping near 808 nm, more than 5.37 W of output power was achieved with a slope efficiency of 41.4%. In the passively Q-switched operation with a Cr4+:YAG crystal, an average output power of 1.98 W with a pulse repetition frequency of 54.8 kHz and a pulse width of 28.5 ns was achieved. The spectroscopic and lasing performance of Nd: LaMgB5O10 indicate that this medium has great potential for application as injection seeding light sources for Nd:glass lasers.

Electron spin dynamics in Ce3+ : YAG crystals: Hyperfine interaction of 4f and 5d electrons

The electron spin dynamics of $\mathrm{C}{\mathrm{e}}^{3+}$ ions in YAG crystals is studied by time-resolved photoluminescence spectroscopy with an alternating left and right circularly polarized continuous-wave laser modulation technique. The electron spin relaxation due to hyperfine interaction with randomly oriented nuclear spins can be efficiently suppressed by a weak external longitudinal magnetic field. The suppression of the hyperfine-induced spin relaxation makes the electron spin polarization increase from 0.001 to 0.016 for the lowest $4f$ state, and from 0.08 to 0.32 for the lowest $5d$ state. The suppression magnetic fields for the $4f$ electrons are several times weaker than that for the $5d$ electrons, dependent on the crystal orientation. The dispersion of the local hyperfine field distribution $\mathrm{\ensuremath{\Delta}}B$ is isotropic and equal to 4.0 mT for the $5d$ electrons, and anisotropic for the $4f$ electrons with $\mathrm{\ensuremath{\Delta}}{B}_{[001]}=0.8\phantom{\rule{0.16em}{0ex}}\mathrm{mT},\mathrm{\ensuremath{\Delta}}{B}_{[110]}=1.1\phantom{\rule{0.16em}{0ex}}\mathrm{mT},\mathrm{\ensuremath{\Delta}}{B}_{[1\overline{1}0]}=2.4\phantom{\rule{0.16em}{0ex}}\mathrm{mT}$. The hyperfine coupling strength for the $4f$ electrons is \ensuremath{\sim}4 times weaker than that for the $5d$ electrons.

Effects of Cr4+ ions on forming Ince–Gaussian modes in passively Q-switched microchip solid-state lasers

The effects of Cr4+ ions on forming Ince–Gaussian (IG) laser modes in a tilted pumped Cr4+:YAG passively Q-switched (PQS) Nd:YAG microchip lasers has been studied experimentally and theoretically. The formation of Cr4+-ion domains in Cr4+:YAG crystal has been proposed based on the spatial distribution of Cr4+ ions in Cr4+:YAG crystal. The spatial modulation effect of Cr4+-ion domains on selecting a transverse mode has been investigated based on their periodic distribution and nonlinear absorption of the Cr4+ saturable absorber. The formation of IG modes in the Nd:YAG/Cr4+:YAG PQS microchip laser under tilted pumping has been demonstrated theoretically with the spatial modulation of the Cr4+-ion domains in Cr4+:YAG crystal and the inversion population distribution, by taking account of the thermal lens effect. The IG modes selected theoretically in the Nd:YAG/Cr4+:YAG PQS microchip laser are in good agreement with experimentally obtained IG modes. This work provides a theoretical model of the selection of IG modes with Cr4+-ion domains in a tilted beam pumped Nd:YAG/Cr4+:YAG PQS microchip laser to produce efficient, stable and controllable IG laser modes.

The characteristics of high-quality Yb:YAG single crystal fibers grown by a LHPG method and the effects of their discoloration.

Single crystal fibers (SCFs), especially ytterbium (Yb) doped crystal fibers, have great potential in the field of high-power lasers. Colorless Yb:YAG single crystal fibers were fabricated using a laser heated pedestal growth (LHPG) method with a diameter fluctuation of less than 2% and a length to diameter ratio greater than 320 : 1. An abnormal color issue exists with respect to Yb:YAG crystals. The origin of coloration was studied via density functional theory, single-crystal X-ray diffraction, XPS and Raman spectroscopy and it was confirmed that the cyan coloration of Yb:YAG crystals is due to oxygen vacancies. Yb:YAG SCFs prepared via the LHPG method could avoid this type of defect due to the large specific surface area and melt convection caused by surface tension. The fundamental properties of the cyan Yb:YAG crystal source rod and colorless Yb:YAG SCFs were systematically investigated. The colorless Yb:YAG SCFs have higher infrared transmittance and thermal conductivity. The distributions of Yb3+ along the radial and axial directions were also measured. Meanwhile we demonstrated the propagation loss and a fiber laser using the colorless Yb:YAG SCFs, obtaining a minimum loss coefficient of 0.008 dB cm−1 and a maximum continuous-wave (CW) output power of 3.62 W. The colorless Yb:YAG SCFs with good thermal conductivity, low propagation loss, wide transparency and uniform ion distribution show promise for acting as the host material in single-mode lasers.

空气导热作用下Nd∶YAG晶体温场特性

空气导热作用下Nd∶YAG晶体温场特性

基于Nd∶YAG/Cr∶YAG复合晶体结构的被动调Q固体微片激光器

基于Nd∶YAG/Cr∶YAG复合晶体结构的被动调Q固体微片激光器

利用Cr 4+∶YAG晶体的各向异性提高输出激光消光比的实验研究

利用Cr ⁴⁺∶YAG晶体的各向异性提高输出激光消光比的实验研究

基于共掺杂Dy-Tb∶YAG晶体的全固态黄光激光特性研究

基于共掺杂Dy-Tb∶YAG晶体的全固态黄光激光特性研究

Prospective scintillation electron detectors for S(T)EM based on garnet film scintillators.

The performance of a scintillation electron detector for a scanning electron microscope and/or a scanning transmission electron microscope (S(T)EM) based on new epitaxial garnet film scintillators was explored. The LuGAGG:Ce and LuGAGG:Ce,Mg film scintillators with chemical formula (Ce0.01 Lu0.27 Gd0.74 )3-w Mgw (Ga2.48 Al2.46 )O12 were prepared and their cathodoluminescence (CL) and optical properties were studied and compared with the properties of current standard bulk single crystal YAG:Ce and YAP:Ce scintillators. More specifically, CL decay characteristics, CL emission spectra, CL intensities, optical absorption coefficients, and the refractive indices of the mentioned scintillators were measured. Furthermore, electron interaction volumes with absorbed energy distributions, photomultiplier (PMT) photocathode matchings, modulation transfer functions (MTF), and the photon transport efficiencies of scintillation detectors with the mentioned scintillators were calculated. A CL decay time for the LuGAGG:Ce,Mg film scintillator as low as 28 ns with an afterglow of only 0.02% at 1 μs after the e-beam excitation was observed. As determined from calculated MTFs, the scintillation detectors with the new film scintillators lose contrast transfer ability above 0.6 lp/pixel, while the currently commonly used YAG:Ce single crystal scintillators already do so above 0.1 lp/pixel. It was also calculated that the new studied film scintillators have an 8% higher photon transfer efficiency, even for a simple disk shape compared with the standard bulk single crystal YAG:Ce scintillator. The studied LuGAGG:Ce,Mg epitaxial garnet film scintillators were evaluated as prospective fast scintillators for electron detectors, not only in S(T)EM but also in other e-beam devices.

Improvement of single pulse energy and laser efficiency by co-doping Cr3+ ions into the Er:YAG crystal

We demonstrated an improvement of laser performance by co-doping Cr3+ into Er:YAG crystal grown by the Czochralski method. The result of X-ray rocking curve suggested that the crystal had high crystalline quality. Two strong absorption bands centered at 450 and 596 nm indicated the Cr,Er:YAG crystal was more suitable for xenon lamp pumping. A maximum single pulse energy of 1.52 J was obtained on the Cr,Er:YAG crystal operated at 5 Hz and 2.94 μm, corresponding to the slope efficiency and electrical-to-optical efficiency of 1.80% and 1.28%, but those of the Er:YAG crystal were only 0.99 J, 1.31% and 0.83%, respectively. Therefore, the Cr,Er:YAG crystal may be a potentially mid-infrared radiation-resistant laser material with higher single pulse energy and efficiency.

Specklegram temperature sensor based on femtosecond laser inscribed depressed cladding waveguides in Nd:YAG crystal

In this paper, waveguide specklegram sensor (WSS) in Nd:YAG crystal for temperature sensing based on the average intensity variation of speckle patterns has been demonstrated. The temperature sensing resolution of the WSS has been identified as high as 0.05 °C. WSS in diverse-guiding geometries with different dynamic range for the temperature sensing has been obtained. In addition, the WSS own a much more sensitive performance to temperature variation when the laser with shorter wavelength and higher power is utilized. Benefit from the compact structure, WSS can be integrated in to a lab-on-chip system offering real-time monitoring of temperature.

Anomalous passive Q-switching induced by Cr4+:YAG: with pulse repetition rate approaching up to 1 MHz

Anomalous passive Q-switching behavior was demonstrated in an Yb:KLu(WO4)2 laser, with a Cr4+:YAG crystal plate acting as saturable absorber whose initial transmission amounted to 99.3%. In stable Q-switched operation realized under high output coupling of 80%, 1.83 W of average output power was produced at a pulse repetition rate of 0.97 MHz, far beyond the upper limit imposed by the recovery time of the saturable absorber. The largest pulse energy, shortest pulse duration, and highest peak power were, respectively, 1.89 µJ, 39 ns, and 48.5 W. The high-repetition-rate passive Q-switching performance shows a close similarity to some Yb-ion lasers passively Q-switched by 2D saturable absorbers.

Enhanced optical linearity and nonlinearity of Nd:YAG crystal embedded with Ag nanoparticles by prior Zn ion implantation

Nonlinear optical properties of nanocomposites exhibit wide nonlinear optical applications, but the nonlinear coefficient is not sufficiently high that it limits the potential application. Thus, we improve the nonlinear optical response of Nd:YAG by dual implantation with Zn and Ag ions to induce the formation of Ag nanoparticles (NPs) in the surface of a crystal. And the structural and optical properties of the NPs embedded in the Nd:YAG have been investigated. The surface plasmon resonance (SPR) absorption of Ag NPs in Nd:YAG crystal shows ~3 times enhancement with a narrower spatial distribution of NPs. Meanwhile, third-order nonlinear coefficients of the crystal embedded with NPs increase to 8 orders of magnitude larger than that of pure Nd:YAG due to the SPR effect. Furthermore, annealing can further modify SPR and nonlinear optical properties owing to improved crystalline structure. The present work provides an alternative route for enhancing the nonlinear optical properties and potential application in optical devices.

Nanodefects in YAG:Ce phosphors

Since the mid-1990s, phosphors have played a key role in emerging solidstate white-lighting technologies that are based on combining a near-UV or blue solid-state light source with downconversion to longer wavelengths. Almost all of them used phosphorescreted a crystalline oxide, nitride, or oxynitride host that is appropriately doped with Gd, Ce or Eu. Activation of phosphors by rare earth elements, leads to the formation of defects in the lattice and due to the change in the luminescent properties. This paper presents the new original model of energy transfer in the YAG crystals, which is a good description of the possible luminescence transitions in crystals. The morphology, spectra and kinetics characteristics of the luminescence of industrial phosphor excited by electron and laser radiation were investigated. The obtained theoretical and practical data are good agreement with each other, and thus are of great interest for understanding the nature of luminescence.

High-Pulse-Energy Passively Q-Switched 1,123 nm Laser with a Nd:GdYAG Mixed Garnet as Laser Medium

We demonstrate a diode-pumped passively Q-switched Nd:GdYAG mixed garnet laser at 1,123 nm. A Cr4+:YAG crystal with an initial transmission of 97% is used as the saturable absorber. The maximum average output power is 1.05 W at an absorbed pumping power of 8.12 W. A single-pulse energy can reach up to 78.9 μJ, with a corresponding pulse repetition rate of 13.3 kHz.

An Intracavity-Triggered Passively-Switched Nd:YVO4 Laser

We demonstrate an intracavity-triggered passively Q-switched Nd:YVO4 laser within a diode-end-pumped configuration. We employ a Cr4+:YAG saturable absorber as the passive Q switch and an Nd:LiYF4 (YLF) laser as the laser triggering of the Q-switched laser. Since we use the same Cr4+:YAG crystal and output coupler with the Nd:YVO4 laser, the Cr4+:YAG Q switch is triggered inside the Nd:YLF laser cavity. As a result, the timing jitter in standard deviation of Nd:YVO4 laser can be reduced to 16 ns.