Determination of the phase of the complex nonlinear refractive index by transient two-wave mixing in saturable absorbers.

The ratio of the imaginary part to the real part of the complex nonlinear refractive index has been measured by transient two-wave mixing in acridine-orange-doped fluorophosphate glass, fluorescein-doped boric-acid glass, and ruby at argon-ion wavelengths. The method enables the individual signs of the components of the nonlinear index to be obtained. A simple theory based on a single homogeneously broadened absorption from the ground state agrees with measurements of the phase of the nonlinear index in acridine but not in fluorescein, where our data suggest that excited-state absorption plays an important role.

High-power narrow-linewidth Er(3+)-doped fiber laser.

We describe a high-power Er(3+) laser that produces 56 +/- 2 and 96 +/- 5 mW of power at room and liquid-nitrogen temperatures, respectively. Slope efficiencies of 10 +/- 1% and 14 +/- 1% with corresponding thresholds of 44 +/- 4 and 6.8 +/- 0.

Intensity ratios of (2)D(5/2,3/2)?(2)S doublets in the two-photon absorption spectrum of Rb and Cs.

Absorption ratios of doublets arising from n(2)D(5/2,3/2)? n'(2)S transitions in Rb (n = 5-9, n' = 5) and Cs (n = 7-13, n' = 6) were measured by Doppler-free two-photon spectroscopy using a thermionic ion detector. The observed ratios agree with calculated values for transitions to the higher levels but differ significantly for levels n = 5 in Rb and n =7, 8 in Cs. These experiments also provide new lower bounds for the ionization potentials of Rb(2) (3.