Deep and shallow trap contributions to the ionic current in the thermal-electric field poling in soda-lime glasses.

In this paper, we investigate the contribution of deep and shallow trapped ions on the second-order nonlinearity during typical poling procedures in soda-lime glass. The zero-electric field potential barriers of each contribution were estimated. The shallow traps, measured through the electrical ionic current, was determined as ~0.34 eV; while deep trap activation energy, measured by means of the thermal/electric field activated luminescence, was estimated ~3.8 eV. The traps show different dependence on its thermal energy onset for different applied electric field. The ionic current is linearly dependent on the electric field. The luminescence has a minimum electric field ~3.6 kV/cm and thermal energy ~31 meV (~87 degrees C) to occur. The average ionic jump lengths for both processes are also estimated, and the deep trap length is about ten times shorter than the shallow trap one. Samples poled at the border of the luminescence onset parameters revealed that the higher its contributions the more stable the induced second order nonlinearity.

Fourfold output power enhancement and threshold reduction through thermal effects in an Er(3+)/Yb(3+)-codoped optical fiber laser excited at 1.064 mum.

Thermally induced output power enhancement and threshold reduction in an Er(3+)/Yb(3+) -codoped optical fiber laser at 1.54mum pumped by 1.064-mu;m cw radiation is demonstrated. Steady fourfold output power increase and threshold decrease were achieved by heating of the Yb(3+) -sensitized Er(3+) -doped fiber laser medium in the temperature range 23-150 degrees C degrees . The laser efficiency thermal behavior is assigned to the temperature-dependent effective absorption cross section of the ytterbium sensitizer through the so-called multiphonon-assisted anti-Stokes excitation process.

Two-photon-resonant photoinduced second-harmonic generation in Er(3+)-doped germano-aluminosilicate optical fibers pumped at 1.319 microm.

The growth of a two-photon-resonant photoinduced second-harmonic signal at 660 nm in Er(3+)-doped GeO(2)-Al(2)O(3)-SiO(2) single-mode optical fibers pumped by a Nd:YAG laser at 1.319 microm is reported. Defect states in the band gap are optically excited through a resonant two-photon absorption process connecting the (4)I(15/2)-(4)F(9/2) energy levels of the erbium ions present in the fiber core. As a result a periodic X((2)) grating is formed, and efficient second-harmonic generation takes place. For erbium-free GeO(2)-doped silica test fibers no second-harmonic signal has been detected, even after hours of seeded preparation process.

Nondegenerate two-wave mixing in GdAIO(3):Cr(3+).

We have measured the nearly degenerate two-wave mixing in GdAlO(3):Cr(3+) crystals. In contrast to that in other chromium-doped materials, the signal in this sample arises from a mixed phase absorption grating where the absorption contribution is intensity dependent. The real (n(2)') and the imaginary (n(2)'') parts of the nonlinear index of refraction, the saturation intensity, and the excited-state lifetime are determined. The ratio r = n(2)''/n(2)' changes linearly with the intensity. Owing to saturation, the grating presents anharmonicities that give rise to self-diffracted beams (forward four-wave mixing). For comparison, results are also presented for ruby and alexandrite.