Orthorhombic PbCO3, known as natural crystal cerussite, is presented as a new Stimulated Raman Scattering (SRS)‐active crystal. With picosecond laser pumping high‐order Raman‐induced χ(3) generation is observed. All registered Stokes and anti‐Stokes sidebands in the visible and near‐IR are identified and attributed to the SRS‐promoting phonon mode A1g of the carbonate group, with ωSRS ≈ 1054 cm−1. The first Stokes steady‐state Raman gain coefficient in the visible spectral range is estimated as well to a value not less than 4.6 cm·GW−1. 相似文献
In single crystals of the beryllium silicate Be2SiO4 with trigonal symmetry , known also as the mineral phenakite, χ(3)‐nonlinear lasing by stimulated Raman scattering (SRS) is investigated. All observed Stokes and anti‐Stokes lasing components are identified and ascribed to a single SRS‐promoting vibration mode with ωSRS ≈876 cm−1. With picosecond single‐wavelength pumping at one micrometer the generation of an octave‐spanning Stokes and anti‐Stokes comb is observed. 相似文献
The non‐centrosymmetric polar tetragonal (P 41) barium antimony tartrate trihydrate, Ba[Sb2((+)C4H2O6)2]·3H2O, was found to be an attractive novel semi‐organic crystal manifesting numerous χ (2)‐ and χ (3)‐nonlinear optical interactions. In particular, with picosecond single‐ and dual‐wavelength pumping SHG and THG via cascaded parametric four‐wave processes were observed. High‐order Stokes and anti‐Stokes lasing related to two SRS‐promoting vibration modes of the crystal, with ωSRS1 ≈ 575 cm?1 and ωSRS2 ≈ 2940 cm?1, takes place. Basing on a spontaneous Raman investigation an assignment of the two SRS‐active vibration modes is discussed.
Hexagonal Ca5(PO4)3F, known as natural crystal fluorapatite and oldest host‐crystal for Ln3+‐lasant ions, is presented as a Raman‐active material. High‐order Raman‐induced χ(3)‐nonlinear processes are discovered in natural crystals of fluorapatite under picosecond pumping at 1.064 μm and 0.532 μm wavelength. A multitude of Stokes and anti‐Stokes components is generated in the ultraviolet, visible and near‐infrared spectral region by stimulated Raman scattering (SRS) and Raman four‐wave mixing (FWHM), resulting in a frequency comb with a width of 520 THz. The spectral lines are identified and attributed to the ν1(Ag) vibration mode of the tetrahedral [PO4] units which is related to a Raman shift of ωSRS ≈ 965 cm−1. The first Stokes steady‐state Raman gain coefficient in the near‐infrared spectral range is estimated to be >0.38 cm·GW−1. Finally, a short review of SRS‐promoting vibration modes and observed χ(3)‐ nonlinear interactions in all known SRS‐active natural crystals (minerals) is given.
In single crystals of orthorhombic YAlO3, widely known as a host‐matrix for Ln3+‐lasant ions, many‐phonon stimulated Raman scattering interactions as well as different manifestations of cascaded and cross‐cascaded nonlinear χ(3)↔χ(3) processes are initiated by picosecond laser pulses. The scientific and applicative potential of YAlO3 crystals is considerably expanded by the demonstration of its SRS properties. In particular, the studies revealed the manifestation of eight χ(3)‐active vibrational modes. The corresponding Stokes and anti‐Stokes lines have been assigned and the steady‐state Raman gain coefficients related to the strongest phonon mode have been estimated. In addition, a short review presents the stimulated emission channels of its Ln3+‐ions together with some χ(3)‐nonlinear laser properties of crystals belonging to the binary Y2O3‐Al2O3 system. 相似文献
Fundamental understandings of surface chemistry and catalysis of solid catalysts are of great importance for the developments of efficient catalysts and corresponding catalytic processes, but have been remaining as a challenge due to the complex nature of heterogeneous catalysis. Model catalysts approach based on catalytic materials with uniform and well-defined surface structures is an effective strategy. Single crystals-based model catalysts have been successfully used for surface chemistry studies of solid catalysts, but encounter the so-called “materials gap” and “pressure gap” when applied for catalysis studies of solid catalysts. Recently catalytic nanocrystals with uniform and well-defined surface structures have emerged as a novel type of model catalysts whose surface chemistry and catalysis can be studied under the same operational reaction condition as working powder catalysts, and they are recognized as a novel type of model catalysts that can bridge the “materials gap” and “pressure gap” between single crystals-based model catalysts and powder catalysts. Herein we review recent progress of surface chemistry and catalysis of important oxide catalysts including CeO2, TiO2 and Cu2O acquired by model catalysts from single crystals to nanocrystals with an aim at summarizing the commonalities and discussing the differences among model catalysts with complexities at different levels. Firstly, the complex nature of surface chemistry and catalysis of solid catalysts is briefly introduced. In the following sections, the model catalysts approach is described and surface chemistry and catalysis of CeO2, TiO2 and Cu2O single crystal and nanocrystal model catalysts are reviewed. Finally, concluding remarks and future prospects are given on a comprehensive approach of model catalysts from single crystals to nanocrystals for the investigations of surface chemistry and catalysis of powder catalysts approaching the working conditions as closely as possible. 相似文献
