Theory and design of an integrated optical sensor based on a Mach-Zehnder interferometer

In this work the feasibility of a high sensitivity integrated gas sensor based on Mach-Zehnder Interferometer on LiNbO3 substrate has been studied. The device is designed in order to perform the Differential Optical Absorption Spectroscopy (DOAS) analysis, through the Fourier Spectroscopy Techniques. The spectral range attainable is expected to span between 0.4 and 4.0 gm. Computer simulations have evaluated the performance of the device, indicating that a spectral resolution between 0.1 nm and 0.3 nm can be envisaged on 20 nm spectral windows. This can allow, in principle, a sensitivity for gas traces in the "p.p.b." range. High Energy Ion Implantation was successfully used to obtain integrated single-mode optical waveguides on LiNbO3. The same technique will be used for the Mach-Zehnder Interferometer fabrication.