Polysilane-Based Thin Films with High Photosensitivity
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Polysilane-Based Thin Films with High Photosensitivity K. Simmons-Potter,*† G. M. Jamison, ‡ B. G. Potter, Jr., ‡ W. J. Thomes, Jr. † and C. C. Phifer† †
Laser, Optics and Remote Sensing Department, Sandia National Laboratories, Albuquerque, NM 87185-1423, U.S.A. ‡ Materials Chemistry Department, Sandia National Laboratories, Albuquerque, NM 87185-1411, U.S.A.
ABSTRACT The present work investigates the intrinsic photosensitivity of a family of poly(alkyl)(aryl)silanes and poly(hydridophenyl)silane for use in the development of photoimprinted waveguide devices. Limited testing of passive optical behavior (e.g. absorption, refractive index) and photosensitive response was performed for these materials in thin film form. It was determined that the materials exhibited dramatic photobleaching under 248 nm (KrF excimer laser) exposure. Based on a KramersKronig analysis of the absorption changes, refractive index changes on the order of – 0.1 are estimated. Confirmation of this calculation has been provided via ellipsometry which estimates refractive index changes at 632 nm of -0.14 ± 0.01. In addition, embedded strips have been photoimprinted into the material to confirm waveguiding capacity of the films. Possible sources of photosensitivity in this material and its potential for application in various device configurations will be discussed. INTRODUCTION Fiber-based photosensitive Bragg gratings have found utility in the telecommunications sector and as an essential element in remote sensing devices. A materials-based understanding of the origins of photosensitivity, defined here as a photoinduced stable (permanent) change in the material’s refractive index, has grown from the ability to fabricate such devices. Efforts to expand the use of photoimprinted optical devices into integrated photonic architectures require the optimization of photo-induced refractive index changes while providing enhanced materials and process compatibility with the dissimilar materials structures characteristic of photonic integrated circuitry. Pursuit of broadly tailorable materials structures and physical properties to achieve these goals has spurred the evaluation of both engineered inorganic materials with strong photosensitivity1-3 and of the photosensitive response of select organic and molecular hybrid materials. In our research, we have specifically sought to evaluate materials whose UV response was enhanced over that of inorganic glasses. In the present work we examine the family of poly(organosilanes),4,5 whose hybrid organic-inorganic Q12.5.1 Downloaded from https://www.cambridge.org/core. Columbia University Libraries, on 17 Aug 2017 at 16:02:12, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1557/PROC-726-Q12.5
molecular composition has been identified as having an inherently high response to UV irradiation. The large UV-induced absorption change that accompanies polysilane photodegradation is anticipated to correspond to a large change in refractive index.6 Mo
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