Volume 89, Issue 5, 01 March 2001
Index of content:
- LASERS, OPTICS, AND OPTOELECTRONICS (PACS 42)
89(2001); http://dx.doi.org/10.1063/1.1341207View Description Hide Description
A single 5 ns laser pulse is experimentally shown to self-focus in electrically biased Systematic measurements have been conducted in order to characterize the physics of fast photorefractive self-focusing. The influence of the externally applied electric field, the incident energy density, the input beam waist and polarization state are reported.
89(2001); http://dx.doi.org/10.1063/1.1342197View Description Hide Description
The field-dependence of the charge photogeneration efficiency reduces the holographic contrast in an organic photorefractive composite. In this article, the Braun model for field-dependent photogeneration efficiency is incorporated into the standard model of photorefractivity. Using this formalism, the effect on the space-charge field, and thereby holographic index contrast, is calculated directly without the need for empirically found parameters. The dependence of the space-charge field on experimental geometry is also analyzed. A powerful description of the effective space-charge field is thus derived and is experimentally verified. This analysis is then used to compare the observed holographic contrast to that predicted from transmission ellipsometrymeasurements.
89(2001); http://dx.doi.org/10.1063/1.1344216View Description Hide Description
Optical properties of codoped silicasol-gel samples have been studied after the gel to glass transition. Different upconversion emissions have been observed under near infrared excitation at about 1 μm. The ions are excited by means of energy transfer processes from ions. The temporal evolution of the blue-green upconversion emissions coming from ions and their dependence on the excitation intensity at about 1 μm has been studied. The experimental results are in good agreement with a cooperative resonant energy transfer mechanism from ions. An efficient backtransfer process is observed from ions towards ions. The upconversion efficiency, which is limited by this backtransfer process, has been obtained and compared with other upconversion results in similar matrix.