Cooperative, or energy-transfer, upconversion reduces the population of the I13/2 manifold in Er:YAG, increasing the laser threshold, but not, in theory, the slope efficiency [1]. We have measured the cooperative upconversion parameter in Er:YAG using the z-scan technique as a function of Er concentration (0.5% to 5%) with the sample at room temperature (298 K) and 80 K. The value we obtain at ...

An analytical expression for the Z-scan signal from two-level atoms which show a saturable dispersive and absorptive nonlinearity is derived. An approximate solution is obtained for the normalized transmittance and compared with numerical calculations. 2004 Elsevier B.V. All rights reserved.

We report a sensitive single-beam technique for measuring both the nonlinear refractive index and nonlinear absorption coefficient for a wide variety of materials. We describe the experimental details and present a comprehensive theoretical analysis including cases where nonlinear refraction is accompanied by nonlinear absorption. In these experiments, the transmittance of a sample is measured ...

A novel porphyrin derivative bearing one D-π-A-π-D pyrimidine chromophore at the periphery was designed, prepared, and studied using the Z-scan technique, the results showing that this compound exhibits enhanced nonlinear optical (NLO) absorption, refraction and optical limiting responses. The significant NLO properties can be ascribed to an effective combination of distinct nonlinear mechanisms.

Application of a parallel-projection inversion technique to z-scan spectra of multiply charged xenon and krypton ions, obtained by non-resonant field ionization of neutral targets, has for the first time permitted the direct observation of intensity-dependent ionization probabilities. These ionization efficiency curves have highlighted the presence of structure in the tunnelling regime, previou...

The concentration dependence of energy transfer upconversion in Nd:YAG is investigated via the z-scan technique. The ETU coefficient is determined to increase from 35×10 -18 cm 3 /s to 90×10 -18 cm 3 /s when the concentration increases from 0.3 at.% to 1.1 at.%. OCIS codes: (190.7220) Upconversion; (140.3530) Lasers, neodymium; (300.6460) Spectroscopy, saturation.

Efforts are being made to develop a new type of CT system that can scan volumes over a large range within a short time with thin slice images. One of the most promising approaches is the combination of helical scanning with multi-slice CT, which involves several detector arrays stacked in the z direction. However, the algorithm for image reconstruction remains one of the biggest problems in mul...

We report the measurement of Kerr nonlinearity of thin films of GaN by using the eclipsing Z-scan technique. The measurement was performed using 100 fs pulses at 800 nm. We measured a pure refractive signal, whose associated nonlinear Kerr coefficient was n2 = (−7.3 ± 0.4)× 10−14 cm2 W−1.