Elastooptical properties of SiON layers in an integrated optical interferometer used as a pressure sensor

This work presents the design and realization of an integrated optical pressure sensor, which is based on the photoelastic birefringence of thin SiO₂ and SiON layers. The advantage of this well known and controlled silicon technology is that optical and electronic circuits as well as micromechanics can be integrated on the same substrate. The sensor is made of a monomode striploaded Mach-Zehnder interferometer, which is placed on a silicon membrane as the pressure sensitive region. The detector is integrated into the silicon substrate, because a wavelength below 1 μm(He-Ne laser source: 632.8 nm) is used. Experimental and theoretical results of the sensor response are presented that demonstrate that efficient sensors can be designed and fabricated and that the TM-polarization gives the higher sensitivity