Sol-Gel Processed Inorganic and Organically Modified Composites for Nonlinear Optics and Photonics
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SOL-GEL PROCESSED INORGANIC AND ORGANICALLY MODIFIED COMPOSITES FOR NONLINEAR OPTICS AND PHOTONICS PARAS N. PRASAD* *Photonics Research Laboratory, Department of Chemistry, New York at Buffalo, Buffalo, N.Y. 14214
State University of
ABSTRACT The newly emerging field of Nonlinear Optics and Photonics offers tremendous opportunities for material scientists. In this paper, chemical processing using the sol-gel method is described for the preparation of new composite materials of both a silica glass and a V O2 gel with a w conjugated polymer poly-p-phenylene vinylene up to 5d% by weight. The composite films show highly improved optical quality with large third-order nonlinear optical coefficients, the latter from the conjugated polymer. Optical waveguiding through the film has been achieved. Nonlinear optical studies using femtosecond degenerate four wave mixing and power dependent waveguide coupling have been successfully performed. Also, to investigate the use of such films for optical recording, a two-dimensional grating structure has successfully been produced. INTRODUCTION Photonics has been labelled by many as the technology for the 21st century. It is a multidisciplinary field which has captured the imaginations of scientists and engineers worldwide. In my view, this field offers tremendous opportunities for materials scientists. Chemical processing can provide new ceramic composite materials with multifunctionalities needed for photonics applications. In this article I hope to highlight this point. Photonics describes the technology in which a photon is used to transmit, process and store information with an obvious gain in speed, bandwidth and density of information processing. The technology, therefore, deals with high density optical data storage, optical processing of information and image analysis. In addition, there is a need for devices to provide sensor protection against laser threat. Some of the needed operational functions are frequency conversion, light modulation and optical switching. For these functions one needs nonlinear optics which describes processes occurring under the influence of a laser pulse. The resulting polarization in the medium can be written in the form of a power series expansion in the electric field strength as [L1 X(1)-g
, X(2):
+
(+
(1)
The term X the linear susceptibility, describes the linear optical effect such as absorption, refraction, etc. under ordinary light intensities and is related to the refractive index of the medium as 1 + 4X
= n
2
(2)
The terms X(2) and X(3) called second and third order nonlinear susceptibilities, respectively, quantify the second and third order nonlinear optical processes. For all optical processing of information, the important nonlinear process is third order, the manifestations of which are third-harmonic generation and intensity dependence of refractive index. It is the latter which provides the method of light control by light and can be Mat. Res. Soc. Symp. Proc. Vol. 180. @1990 Materials Research Society
742
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