[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

Nonlinear Optical Crystals: A Complete Survey

The control of luminous radiation has extremely important implications for modern and future technologies as well as in medicine. In this Review, we detail chemical structures and their relevant photophysical features for various groups of materials, including organic dyes such as metalloporphyrins and metallophthalocyanines (and derivatives), other common organic materials, mixed metal complexes and clusters, fullerenes, dendrimeric nanocomposites, polymeric materials (organic and/or inorganic), inorganic semiconductors, and other nanoscopic materials, utilized or potentially useful for the realization of devices able to filter in a smart way an external radiation. The concept of smart is referred to the characteristic of those materials that are capable to filter the radiation in a dynamic way without the need of an ancillary system for the activation of the required transmission change. In particular, this Review gives emphasis to the nonlinear optical properties of photoactive materials for the functi...

Nonlinear Optical Materials for the Smart Filtering of Optical Radiation.

Cryogenically cooled solid-state lasers promise a revolution in power scalability while maintaining a good beam quality because of significant improvements in efficiency and thermo-optic properties. This is particularly true for Yb lasers because of their relatively low quantum defect and relatively broadband absorption even at cryogenic temperatures. Thermo-optic properties of host materials, including thermal conductivity, thermal expansion, and refractive index at low temperature, are reviewed and data presented for YAG (ceramic and single crystal), GGG, GdVO4, and Y2O3. Spectroscopic properties of Yb:YAG and Yb:LiYF4 (YLF) including absorption cross sections, emission cross sections, and fluorescence lifetimes at cryogenic temperatures are characterized. Recent experiments have pushed the power from an end-pumped cryogenically cooled Yb:YAG laser to 455-W continuous-wave output power from 640-W incident pump power at an of M2 1.4.

Cryogenic Yb $^{3+}$ -Doped Solid-State Lasers

In the past few years, Ni(OH)2 has been found to be an effective cocatalyst for photocatalytic hydrogen evolution. Herein, we report that it can also be used to enhance the photoreduction of CO2 into chemical fuels. Vertically aligned Ni(OH) 2 nanosheets are deposited onto electrospinning TiO2 nanofibers via simple wet-chemical precipitation to manufacture TiO2/Ni(OH) 2 hybrid photocatalysts. The TiO2 nanofibers can direct the ordered growth of Ni(OH) 2 nanosheets, which have a thickness of 20 nm and uniformly cover the surface of the TiO2 substrate. The TiO2/Ni(OH) 2 hierarchical composite displays remarkably improved photocatalytic CO2 reduction activity compared to that displayed by pristine TiO2 fibers. The bare TiO2 can only produce methane and carbon monoxide (1.13 and 0.76 μmol h−1 g−1, respectively) upon CO2 photoreduction. After loading 0.5 wt% Ni(OH) 2, the methane yield increases to 2.20 μmol h−1 g−1, meanwhile the CO yield is unchanged. Interestingly, alcohols (methanol and ethanol) also appear as products, in addition to CH4 and CO, over the TiO2/Ni(OH) 2 hybrid, and the maximum yield is reached with 15 wt% Ni(OH) 2 loading (0.58 and 0.37 μmol h−1 g−1 for methanol and ethanol, respectively). This can be ascribed to an enhanced charge separation efficiency and higher CO2 capture capacity due to the presence of Ni(OH) 2. These results demonstrate that Ni(OH) 2 can not only improve the total CO2 conversion efficiency, but can also alter the product selectivity upon photocatalysis. This work opens a new pathway for achieving high-efficiency photocatalytic CO2 reduction with Ni(OH) 2 as a cocatalyst.

Hierarchical TiO2/Ni(OH)2 composite fibers with enhanced photocatalytic CO2 reduction performance

Characterization and Adsorption Mechanism of ZrO 2 Mesoporous Fibers for Health-Hazardous Fluoride Removal

The thermal conductivities of Nd:YAG, M(Y,Gd)VO4 crystals were measured at 298 K. The value of Nd:GdVO4 crystal along direction was 11.4 W/mK, which was higher than that of YAG crystal measured to be 10.7 W/mK. The principal refractive indices of Nd:GdVO4 crystal in the temperature range from 20 °C to 170 °C were determined by auto-collimation method. Based on the measured values of refractive indices, the Sellmeier equation and expression of temperature dependence of refractive indices have been obtained. The measured results show that the birefringence Δn is 0.22007 at 20 °C and temperature coefficient of birefringence is 4.33 × 10−6/°C for 1.064 μm. These results prove that the GdVO4 crystal is a laser crystal with excellent thermal and birefringence properties. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Thermal conductivity and refractive indices of Nd:GdVO4 crystals

Electrospun SiO2-MgO hybrid fibers for heavy metal removal: Characterization and adsorption study of Pb(II) and Cu(II).

Nd:YVO 4 crystal has been grown by Czochralski method. The data of thermal expansion and specific heat have been measured. The thermal expansion coefficients along a- and c-axis are α 1 = 2.2 × 10 -6 /K, and α 3 = 8.4 × 10 -6 /K respectively. The specific heat is 24.6 cal/mol K at 330 K. The large anisotropy along c- and a-axis of thermal expansion coefficients is explained by the structure of YVO 4 crystal. 921 mW output laser at 1.06 μm has been obtained with a 3 mm × 3 mm × 1 mm crystal sample when pumped by 1840 mW cw laser diode, and the slope efficiency is 55.5%.

Thermal and Laser Properties of Nd:YVO4 Crystal

A diode-laser-array end-pumped efficient CW Nd:GdVO4 laser at 1.06 μm has been developed. A low-order-mode output power of 14.3 W was obtained at the maximum available pump power of 26 W, giving an optical conversion efficiency of 55% and an average slope efficiency of 62%. The laser output beam quality factor at full pump power was determined to be M2<1.8. It is also shown that only lightly doped Nd:GdVO4 crystals are suitable for high-power end-pumped lasers.

Luyi Zhu

Papers

Characterization and Adsorption Mechanism of ZrO 2 Mesoporous Fibers for Health-Hazardous Fluoride Removal

Thermal conductivity and refractive indices of Nd:GdVO4 crystals

Electrospun SiO2-MgO hybrid fibers for heavy metal removal: Characterization and adsorption study of Pb(II) and Cu(II).

Thermal and Laser Properties of Nd:YVO4 Crystal

Diode-laser-array end-pumped 14.3-W CW Nd:GdVO4 solid-state laser at 1.06 μm