We report an efficient high-power self-frequency-doubling (SFD) Nd:GdCOB laser. The maximum output power is $3.01\mathrm{W}$ at a wavelength of $545\mathrm{nm}$ with an optical efficiency of 20.7%, which, to our knowledge, is the highest SFD laser output power and efficiency yet obtained. By optimizing the configuration and cut orientation of the Nd:GdCOB crystals, a SFD laser at a wavelength of about $530\mathrm{nm}$ was achieved with a maximum output power of $1.32\mathrm{W}$. We propose that these SFD lasers will have promise in applications such as laser displays, medical treatment, spectroscopic analysis, etc.

Ammonium sulfate has been widely used as a control agent in the preparation of yttrium-aluminium-garnet (YAG) transparent ceramics, however, research of its application in the preparation in transparent ceramic yttria has not been intensively studied. Neodymium–doped yttria (Nd:Y₂O₃) nanopowders with controlled morphology and size were synthesized via a urea precipitation method using ammonium sulfate as the additive. The effect of ammonium sulfate was intensively studied throughout the preparation process. Morphology of precursors was found to be evidently affected by the [(NH₄)₂SO₄]/[Nd:Y₂O₃] ratio (measured by weight). Uniform spheres of Nd:Y₂O₃ precursor were obtained without the addition of ammonium sulfate. With increasing amounts of ammonium sulfate added, the scale of the Nd:Y₂O₃ precursors diminished which results in the aggregation of the Nd:Y₂O₃ precursor. Aggregates of coral like particles after precipitation and uniform well dispersed particles after calcinations were obtained as the dosage of ammonium sulfate reached 20 wt%. It was considered to be the optimum state for the preparation of highly sinterable Nd:Y₂O₃ nanopowders. Ammonium sulfate was proved to be a regulator that could mediate the nucleation and growth of the precursor as well as its decomposition behaviour. Results of this paper can contribute to the controllable synthesis of transparent ceramic yttria.

Laser-diode (LD) pumped self-frequency doubling (SFD) Nd:GdCa₄O(BO₃)₃ (Nd:GdCOB) miniature laser was demonstrated. The output power as high as 1.35 W was achieved which is over than five times than previous values for Nd:LnCa₄O(BO₃)₃ (Ln = Y or Gd) SFD lasers and becomes the highest continuous-wave output power in this field to our knowledge. The maximum optical conversion efficiency is 17%. By comparison, we found that the cutting direction along its optimal phase-matching direction out of the principal planes is the determining factor resulting in this watt-level efficient output power. Different with previous studies, the emission wavelength is centered at about 545 nm. We believed that this efficient laser will become the most competitive one in the existing commercial green lasers, especially in the laser display, medical treatment and spectroscopic analysis etc.

In this work, using large-sized single crystals of high optical quality, the optical properties of Ba₂TiSi₂O₈ were systematically investigated, including transmission spectra, refractive indices and nonlinear absorption properties. The crystal exhibits a high transmittance (>84%) over a wide wavelength range from 340 to 2500 nm. The refractive indices in the range from 0.31256 to 1.01398 μm were measured, and Sellmeier’s equations were fitted by the least squares method. The nonlinear absorption properties were studied by using the open-aperture Z-scan technique, with a nonlinear absorption coefficient measured to be on the order of 0.257 cm/GW at the peak power density of 16.4 GW/cm². Such high transmittance and wide transparency indicate that optical devices using the Ba₂TiSi₂O₈crystal can be applied over a wide wavelength range. Furthermore, the small nonlinear absorption observed in Ba₂TiSi₂O₈ will effectively increase the optical conversion efficiency, decreasing the generation of laser damage of the optical device.

The full matrix of electro-elastic constants of sillenite-type crystals Bi₁₂TiO₂₀ (BTO) and Bi₁₂SiO₂₀ (BSO) were determined by the resonance method, with d₁₄ and k₁₄ being on the order of 40–48 pC/N and 31%–36%, respectively. In addition, double-rotated orientation dependence of d₃₃ was investigated, with the maximum values of 25–28 pC/N being achieved in ZXtl45°/54°-cut samples. The electrical resistivity of BSO was found to be two orders higher than that of BTO, being on the order of 7 × 10⁵ Ω cm at 500 °C. The temperature dependence of dielectric and piezoelectric properties were investigated. BSO exhibited a high thermal stability in the temperature range of 25–500 °C, while BTO showed a variation of ~3% in the range of 25–350 °C. The high values of d₁₄ and k₁₄, together with the good thermal stability, make BTO and BSO crystals potential candidates for electromechanical applications in medium temperature range.

Deep-UV nonlinear optical material KBe₂BO₃F₂ (KBBF), fabricated by flux and hydrothermal methods, are studied by single crystal and powder X-ray diffraction (XRD) and neutron diffraction (NPD). Based on the single crystal diffraction data, the standard R32 structure is confirmed for flux grown KBBF, while the Rc structure is identified for the hydrothermally grown KBBF. No clear evidence of hydrogen bonding is found in the crystals by single crystal neutron diffraction. From powder XRD and neutron diffraction, the hydrothermally grown KBBF under investigation is found to be a mixture of two components consisting of 19.8 wt% of the R32 structure and 80.2 wt% of the Rc structure. No phase changes as a function of temperature up to 775 °C are observed for both samples from temperature dependent powder XRD data. However, a large anisotropic thermal expansion of the lattice is shown in the temperature dependent data.