Laser direct writing of waveguide structures in LiNbO₃.

A laser microfabrication technique based on the decomposition of organometallic inks using visible light is described that eliminates the problems of conventional techniques and allows the rapid design and fabrication of waveguide structures in LiNbO3. Several waveguide structures including straight guides and branches have been fabricated and characterized. The narrowest guides were 5 μm wide and supported one to two modes, depending on the initial ink thickness. Single-mode waveguides at 1.3 μm have a propagation loss of 0.7 dB/cm and fiber-waveguide coupling loss of 2 dB. These measurements compare favorably with Ti-indiffused guides formed by conventional techniques. By adding a second step to the process, namely, the laser patterning of gold electrodes, it was possible to fabricate active waveguide devices.