Design and Fabrication of Lithium Niobate Blue-Laser Waveguide Devices

Blue laser can now be successfully integrated on a chip because of the great advance on semiconductor fabrication technology. Devices for potential application at this wavelength can thus be realized. Among them, optical communication system at blue laser wavelength is quite unique for both military and commercial uses. The study of devices in this system is then becoming important.
In this thesis, optical waveguides and electrooptic(EO) modulators at blue laser wavelength, instead of commonly used 1.55µm are studied. Lithium niobate was used as waveguide material because of its durability, optical transparency, large electrooptic coefficients, and strong nonlinearity. Moreover, the problems of narrower single mode waveguide width, more serious lithium outdiffusion, and stronger photorefractive effect are carefully studied and solved.
Single-mode waveguides were first fabricated to obtain appropriate process parameters. Then, Mach-Zehnder modulators are fabricated for studying EO modulation. Upon comparison, it is found that the linewidth of single mode waveguide is wider than that simulated using the index extrapolated from the long-wavelength model. The lithium niobate Mach-Zehnder modulator was modulated at blue laser region, and is found to have a halfwave voltage of 9V and an extinction ratio of 8.5dB. To our knowledge, those are the first reported data, so far.