Stable and large second harmonic generation in sol-gel-processed poled silica waveguides doped with organic azo dye

Sol-gel-processed silica films doped with organic azo dye, Disperse Red 1 (DR1) in a higher concentration of 21.7 wt%, were prepared at a higher baking temperature with corona poling of higher voltage than in other reports to obtain stable and large second harmonic generation (SHG) and film strength. A large effective SHG coefficient of 75 pm/V was measured for the film of 0.2-µm thickness at a fundamental wavelength of 1064 nm, and the value was unvaried for 700 h with no relaxation. Moreover, a waveguide SHG device of four-layer structure with DR1-doped sol-gel film as a top layer was fabricated for the first time, and Cherenkov-type phase-matched SHG was observed successfully.