BURIED OPTICAL WAVE-GUIDE POLARIZER BY TITANIUM INDIFFUSION AND PROTON-EXCHANGE IN LINBO3

Buried optical waveguide polarizers on LiNbO3 have been realized by titanium indiffusion, followed by proton-exchange and annealing. The proton-exchange process decreases the ordinary refractive index and so modifies the index profile of the titanium indiffused waveguide. The measured intensity profile is in good agreement with calculation. An aluminium film absorbs the surface TM mode on z-cut LiNbO3, leaving a buried nearly symmetric TE mode with lower optical loss than surface guided TE mode. The extinction ratio obtained is estimated to be greater than 50 dB / cm at 0.633-mu-m.