Waveguide Fabrications of 4-(4-Dimethylaminostyryl)-1-Methylpyridinium Tosylate (DAST) Crystal(Special Issue on Recent Progress in Organic Molecular Electronics)

概要

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Organic nonlinear optical crystal 4-(p-dimethylaminostyryl)-1-methylpridinium tosylate (DAST) has a larger electro-optic (EO) coefficient than that of LiNbO_3 crystal. Thus, DAST is a promising material for EO switching device. To use its large EO coefficient effectively, a waveguide structure is desirable. We have successfully fabricated two types of DAST crystal optical channel waveguide. One is a serially grafted waveguide combining a DAST and a transparent polymer by using the combination of standard photoprocess and reactive ion-etching (RIE). Because DAST has large optical loss, parts of the waveguide should be composed of transparent polymer with a serially grafted structure with DAST. This structure reduced not only a propagation loss but also input/output losses. This serially graft waveguide fabrication technique for active organic crystal is available to many types of crystals with device function. The other is a channel waveguide made by a photo-bleaching technique. The cladding part of DAST waveguide was photo-bleached by irradiation of UV light. Under and over cladding layer were composed with UV-cured resin that did not dissolve the DAST crystal. This technique is very convenient for making DAST waveguide because of its simple procedure to make core-cladding structure of DAST compared to standard photo-process and RIE.
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2002-06-01