Optical absorption of measured at . Polarized spectra in the ultraviolet limit: , solid curve and , dashed curve. The extrapolated straight lines are used to determine the ultraviolet UV edges. The infrared spectra are unpolarized and the absorption scale is arbitrary above . In the abbreviated formulas W means and Mo means .
Ordinary and extraordinary refractive indices of measured at . The symbols are the experimental points and the curves are the fits to the Sellmeier law with parameters summarized in the inset.
Polarized Raman spectra of . (solid line), (dashed line), and (gray line). For a tetragonal crystal the and axes are equivalent.
polarized optical absorption spectra of (a) and excitation spectra of (b).
photoluminescence spectrum of .
cross sections of . Absorption cross sections (a). Emission cross sections (b). The -polarized photoluminescence (PL) recorded with is included for comparison (squares). Gain cross sections for (c).
fluorescence lifetime obtained by extrapolation to zero pinhole diameter of the decay time constants measured at room temperature.
Cavity configurations used in the cw (a) and mode-locked (b) regimes of the laser.
Single-pass absorption of the thick vs incident pump power measured without lasing (open symbols) and under laser operation (filled symbols) for polarization (a) and polarization (b) and several output coupler transmissions : 1% (circles), 3% (squares), and 5% (triangles).
Output power vs absorbed pump power at of the cw laser for (a) and (b) polarizations using several output coupler transmissions : 1% (circles), 3% (squares), and 5% (triangles). The linear fits shown give the slope efficiencies obtained for each value.
Output power vs incident pump power at for the cw laser using a double-pass pump configuration with the thick sample and several output couplers, (circles), 3% (squares), and 5% (triangles).
Wavelength tunability under single-pass Ti:sapphire laser pumping of the thick sample for and the two polarizations.
Autocorrelation trace with the corresponding fit assuming -pulse shape (a) and spectrum (b) of the femtosecond laser with .
Growth conditions and composition of crystals grown by the TSSG method.
FI ( and ) parameters and calculated SOM CFPs (, , , , , and ) used to calculate the and energy levels of in the and sites of NaLuW. The experimentally determined Yb energy levels are given in parentheses. All energies are relative to the level for the corresponding site. Parameters and energies are given in . Overlap between Yb-ligand (oxygen) orbital wave functions: , effective charge for oxygen: .
Absorption and emission cross sections of in tetragonal double tungstates.
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