Highly sensitive optical waveguide detection of photo reactions and all-optical switching by guided mode organic thin films
1998
Kyoichi Sttaki
All-optical switching and spatial light modulator has attracted much interest especially in the fields of optical data communication and optical parallel data processing. However, no practical devices have been developed except for some prototypes because no materials and device structures with faster and larger photoresponses than liquid-crystal switch have been developed. It is important for optical parallel data processing to select active materials and measure the photoresponsive properties as much as to construct some devices.
In chapter 2, the extinction coefficients of specific ion-pair charge-transfer(IPCT) complexes between polymeric 4,4''
bipyridinium and tetrakis[3, 5-bis(trifluoromethyl) phenyUborate film were estimated by highly sensitive optical waveguide detection system. The thickness of these films estimated from these coefficients almost coincided with that by the ellipsometry.
Highly sensitive polarized absorption measurement by this system was made to analyze the specific orientation of photogenerated radicals in Langmuir-Blodgett films of two amphiphilic IPCT complexes.
In chapter 3, a novel all optical device was proposed based on photo-induced changes of real and/or imaginary-parts of
complex refractive-index in a composite thin film of silver and polymer containing photoresponsive dye. Highly reversible parallel intensity modulation was achieved by using metal phtalocyanines with a rise time less than 20 ns. Tha fall time depend on the dye and the thickness of a polymer film containing it; 3 p s for copper phthalocyanine and 500 p s for zinc phthalocyanine.
In chapter 4, very fast switching and modulation of a reading beam was achieved at the incident-angle of guided-wave mode using photochromic spiropyran-doped polystyrene films by a ns pulsed UV or visible laser as a writing beam. Upon UV irradiation, the reflectance increased by more than l0 times. Both switching ON and OFF were achieved in less than 20 ns. No applied power was required to hold the switched state. An image was also written to the probe beam by inadiation through a patt€rn.
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