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We have demonstrated the output characteristics of optical parametric amplification (OPA) seeded by a supercontinuum (SC) generated in deionized water excited by 1064 nm. The SC spectrum (from 426 to 943 nm) overlaps well with the tuning range of a 355 nm pumped OPA for both the signal and idler. The tunable range covers from 430 to 2035 nm, with a maximum overall energy conversion efficiency of 32% in the OPA stage. A FWHM bandwidth of 54 nm near the degeneracy point from 658 to 760 nm can be generated by using a collinear OPA. Chirping of the SC pulses is also investigated with the OPA technique. The time delay between the 430 nm component and the 567 nm component of the generated SC due to chirp is measured to be -10.72 ps, increasing almost linearly with the wavelength. [c] 2010 Optical Society of America OCIS codes: 190.4410, 320.6629, 320.0320, 010.7340.

In the presence of the ligand N,N-bis(3-pyrazolamide)-1,2-hexahydrobenzene (H2dpyh), three diverse fascinating structures were constructed from different polyoxometalate (POM) anions and CuII/CoII ions: {Cu8(μ2-OH)2(dpyh)4[CrMo6(OH)5O19](H2O)8}·2[CrMo6(OH)6O18]·4H2O (1), {Co(H2dpyh)[β-Mo8O26]0.5(H2O)} (2) and {Co3(H2dpyh)2[TeMo6O24](H2O)6} (3). Complexes 1–3 were characterized through single crystal X-ray diffraction, IR spectra and powder X-ray diffraction. Single-crystal analysis shows that complexes 1–3 contain internal flexible metal–pyrazole loops and different POMs, which exhibit 1D chain or 2D layer networks, respectively. Directed by the coordination modes of the POM anions and central metals, the shape and size of these metal–pyrazole loops can be tuned, which further influence the final structures and catalytic properties of complexes 1–3. The catalytic activity of these POM-based complexes toward the oxidation of thioether derivatives has been investigated, which proved the effect of metal–pyrazole loops and their final structures on the catalysis of the title complexes as heterogeneous catalysts. [ABSTRACT FROM AUTHOR]

We report the optical parametric properties of cesium lithium borate (CLBO) crystals pumped by LTV radiation of the fourth-harmonic generation at 266 nm and the third-harmonic generation at 355 nm of a picosecond Nd:YAG laser. A special optical design was used to avoid damage to the optical elements by the UV-pumped beam at 266 nm. The optical parametric generator (OPG)/optical parametric amplifier (OPA) of the 266-nm-pumped CLBO covers the tuning range from 347 nm in the UV to 1137 nm in the near IR. The 355-nm-pumped CLBO OPG/OPA, on the other hand, is tunable from 447 to 1725 nm. The experimental tuning curves for each CLBO OPG/OPA were measured and compared with the theoretical tuning curves. With a double-pass OPG configuration and a pumping intensity of ~6 GW/[cm.sup.2], the maximum conversion efficiency, including both the signal and the idler, was ~11% for the 266-nm-pumped CLBO and is greater than 16% for the 355-nm-pumped CLBO without taking into account the surface losses from the uncoated elements. The bandwidth of this double-pass CLBO OPG at various wavelengths was measured and compared with other optical parametric systems. Because of the small angular dispersion of CLBO, the bandwidth of the OPG and OPA systems is exceptionally narrow, especially for the 266-nm-pumped system. Without the use of any dispersion element, the bandwidth of the 266-nm-pumped system can be as narrow as 0.22 nm at wavelengths far from the degenerate point. Comparison between the experimental bandwidth and the theoretical calculation shows that the bandwidth of the UV-pumped CLBO OPG/OPA is limited mainly by the divergence of the pump beam. OCIS codes: 190.4410, 190.4360, 190.4400.

We report a 10-Hz, highly efficient, widely tunable (from the visible to the IR), broadband femtosecond optical parametric generator and optical parametric amplifier (OPA) in BBO, LBO, and CBO crystals pumped by the frequency-doubled output of a regeneratively amplified Ti:sapphire laser at 400 nm. The output of the system is continuously tunable from 440 nm to 2.5 [[micro]meter] with a maximum overall efficiency of [approximately]25% at 670 nm and an optical conversion efficiency of more than 36% in the OPA stage. The effects of the seed beam energy, the type of the crystal and the crystal length, and the pumping energy of the output of the OPA, such as the optical efficiency, the bandwidth, the pulse duration, and the group velocity mismatch between the signal and the idler and between the seeder and the pump, are investigated. The results provide useful information for optimization of the design of the system.