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We report measurements of the nonlinear refractive index, n 2 , and the nonlinear absorption coefficient, ␣ 2 , of Pb͑PO 3 ͒ 2 -WO 3 glasses. The measurements were performed using 100 fs ͑17 ps͒ laser pulses at 800 nm ͑1064 nm͒. Positive values of n 2 ϳ 10 −19 m 2 / W and negligible ␣ 2 were measured. The results show that the nonlinearity is faster than 100 fs and it is observed an increase of n 2 with the increasing of the WO 3 amount in the samples. The Boling, Glass, and Owyoung model, based on the semiclassical harmonic oscillator model, was used to predict the values of n 2 , with basis on the values of the linear refractive index of the samples.

The authors report experimental results on the optical limiting behavior of a bismuth oxide-based glass by exciting the samples with nanosecond laser pulses at 532 and 598 nm. The results show that two-photon and free-carrier absorption processes contribute for the nonlinear absorption. Values for ␤, the two-photon absorption coefficient, and e , the absorption cross section due to free carriers, were determined. The values of ␤ and e are dependent on the amount of bismuth oxide in the glass composition. © 2006 American Institute of Physics. ͓DOI: 10.1063/1.2393161͔ Presently, there is an increasing effort in integrating alloptical devices in more complex structures that allow controlling light signals through amplification, modulation, and switching. Besides these characteristics, limiting the amplitude of a light signal is extremely relevant because optical elements have to be protected against overillumination. 1 Approaches to achieve this are based on the use of active and passive devices. Active devices rely on feedback loops, which control an aperture allowing that a greater or smaller amount of light pass through it, regulating the incoming light flux. Due to the electronic circuits required to drive such systems, they are in general too slow to follow the steep intensity variation of a nanosecond or a picosecond light pulse. On the other hand, passive devices that exploit the nonlinear ͑NL͒ optical susceptibility of a given substance to the incoming light field are more appropriate systems because the NL response may be ultrafast.There are different mechanisms that allow operating passive optical limiters such as NL refraction, 2 induced scattering, 3 free-carrier absorption ͑FCA͒, 4 reverse saturable absorption, 5 and two-photon absorption ͑TPA͒. 6 There is also the possibility of improving the performance of an optical limiter by combining some of the above mentioned processes in a single device, 7,8 as well as by exploiting material's nonlinearity in a multipass configuration. 9 In any case, the NL properties of the material used determine the performance of the device.In this work, we report on the optical limiting behavior of oxide-based glasses. The samples were fabricated following the procedure described in Ref. 10. The glasses were synthesized by melting and quenching the powdered starting materials: bismuth oxide ͑Bi 2 O 3 ͒, zinc oxide ͑ZnO͒, and boron oxide ͑B 2 O 3 ͒. The concentration of Bi 2 O 3 was varied in the ternary system ͑Bi 2 O 3 -ZnO-B 2 O 3 ͒ and the glass compositions studied in this work were ͑in mol %͒ as follows: 25.0 Bi 2 O 3 -37.5 ZnO-37.5 B 2 O 3 ͑sample BZH2͒ and 12.5 Bi 2 O 3 -43.75 ZnO-43.75 B 2 O 3 ͑sample BZH7͒. The samples with a thickness L = 1.0 mm were excited either by the second harmonic ͑SH͒ of a Q-switched Nd:YAG ͑yttrium aluminum garnet͒ laser ͑7 ns, 5 Hz͒ or at 598 nm, obtained from a homemade dye laser pumped by the SH of the same Nd:YAG laser. To control the incident intensity on the sample, the laser beam was made to pass through a halfwave plate combined...

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