Second-order nonlinearity of nonpoled polymeric thin films doped with pyrylium salts with blue window characteristics

Abstract

A novel nonlinear organic ionic material, or pyrylium salt dye, is synthesized and doped in the polymer matrix. These guest-host-type polymer films, which have no absorption in the blue-wavelength region, have second harmonic generation (SHG) activities without the electric-field poling process. The nonlinear optical coefficient d33 is estimated as 1.10 pm/V at a 15 wt % of dye concentration. The nonlinearity is stable at room temperature and at 120 °C. The SHG device is fabricated using the nonpoled polymer film, and Cerenkov-type phase-matched SHG is observed.