Development of highly efficient polymeric frequency doubler using novel fabrication technique of domain inversion.

点击翻译按钮获取中文摘要

Recently organic nonlinear optical (NLO) materials have been extensively investigated because of their large second-order nonlinear optical coefficients and ultra fast response in the field of optoelectronics. A conversion efficiency of frequency doubler is proportional to the optical density of fundamental beam. The waveguide geometry has advantages for nonlinear optical (NLO) applications, because of the high power density that can be achieved over a long propagation length and utilization of diagonal tensor components. In order to obtain a highly efficient second harmonic generation (SHG), the materials match the phase velocity over the long propagation distance for light at fundamental and harmonic waves. By carefully adjusting the waveguide thickness the dispersion of the medium allows different mode at the two wavelengths to have the same effective refractive index n_<eff>, which is called as modal dispersion phase-matching (PM). The effective refractive index of waveguide critically depends on the waveguide dimensions. Therefore fabrication tolerance of waveguide dimension to fulfilll phase-matching condition is limited to less than a few nm. Furthermore optical-field overlap must be large between the propagating waveguide modes to improve a conversion efficiency. In general, it is difficult to obtain large dimension tolerance, together with high overlap integral for modal dispersion phase-matching. Here we report that five-layr organic waveguides prepared by Langmuir-Blodgett techniques exhibit high overlap integral as well as large fabrication tolerance of thickness up to 56 nm. This large fabrication tolerance for phase-matching is 8.6 times larger than that of conventional three layr waveguide.