FABRICATION OF FERROELECTRIC-DOMAIN-INVERTED GRATINGS FOR LINBO3 2ND-HARMONIC GENERATION DEVICES BY VOLTAGE APPLICATION

To realize a compact short-wavelength coherent light source, developme nt of an LiNbO3 waveguide quasi-phase matched second harmonic generati on devices is expected. To realize these devices, fabrication of the d omain-inverted grating is important. The authors discuss the fabricati on of a grating with a period of about 3 mu m near the surface of the z-cut LiNbO3 crystal (with a thickness of 0.5 mm) by applying voltage. As the periodic electrode structure, the ladder electrode and the cor rugation electrode were investigated. The distribution of the z compon ent of the electric field induced under the periodic electrode was com puted theoretically so that the structure of the periodic electrode ef fective for the grating fabrication was determined. From the experimen tal investigation, it was found that the domain inversion was more lik ely to occur on the Ct side and the application of the current limited pulse voltage (similar to 10 kV, width of 1 similar to 40 ms) was eff ective and that a domain-inverted grating could be fabricated almost u niformly under the entire electrode if the current-limiting value and the pulsewidth were adequate. When a ladder electrode (electrode linew idth/period similar to 0.2) is used in vacuum and when a corrugation e lectrode was used in insulation oil, suitable structures can be fabric ated for the device, which is uniform in the waveguide cross section a nd the inverted width to the uninverted width was close to one to one under the periodic electrode.