Four-photon absorption cross-section measurements in UV fused silica at 473 nm.

With the use of I- and z-scan techniques, the four-photon absorption cross section in a UV fused silica sample has been measured to be σ4=(1.0±0.5)×10-115 cm8 s3 at 473 nm. This value is more than an order of magnitude lower than that known for other optical materials (KBr, KI, NaCl, TeO2, and GeS2).

Dynamic photolytical actinometry of the vacuum-ultraviolet radiation produced by multichannel surface discharges of submicrosecond duration.

Absolute measurements of the vacuum-ultraviolet (VUV) radiation power produced by a planar broadband optical source of submicrosecond light pulse duration are carried out in the transient regime of formation of a photodissociation (bleaching) wave in a photodecomposing absorptive medium. The source is based on a multichannel surface discharge initiated in ArN(2) gas mixtures on the area of approximately 0.1 m(2). The energetic characteristics of the produced VUV radiation are determined on the basis of spatially and temporally resolved observations of the pulsed photolysis of XeF(2) vapors. It is shown that the photon flux intensity produced by the source within the spectral range of 120-200 nm reaches 1.1 x 10(23) photonscm(2) s corresponding to the effective brightness temperature of discharge plasma of 20 kK and to the intrinsic efficiency of the discharge VUV emission of 3.2%. Numerical simulations of the photolysis process show a rather weak sensitivity of the results to the fraction of discharge radiation emitted into the line spectrum, as well as to the angular distribution of emitted radiation. The spectral band of measurements can be selected according to the choice of parent photodecomposing particles.

Transport of broadband arbitrary radiation through a bleaching medium.

A novel analytical treatment of the transport of broadband radiation arbitrarily directed through a bleaching medium is presented. The emphasis is on the principle features of photodecomposition (bleaching) wave formation. Considering radiation from a uniform planar source with stable radiative characteristics and media with a uniform initial distribution of the absorptive component, we show that this problem has an asymptotic stationary solution for a wave propagating through a medium characterized by a photodecomposition spectrum without any portion in which the absorption cross section continually runs down to zero.