Development of a VO2/Si Optical Modulator with Co-Integrated Micro Heater

We present the development of an optical modulator utilizing the large change in optical transmission of a vanadium dioxide (VO2) nano layer on a Silicon (Si) waveguide due to a thermally induced first-order phase transformation. The design includes co-integrated Au microstructures that induce the phase transformation in the VO2 nano layer through local Joule heating. A fabrication process is developed comprising electron-beam lithography, cryogenic reactive ion etching and high-temperature VO2 sputtering. The critical electrical current required to induce the VO2 phase transformation is investigated by finite element simulations of the local temperature profile and electrical resistance measurements on test samples. Simulations of optical transmission are performed to evaluate the extinction ratio (ER) for different geometrical dimensions of the VO2 nano layer and an intermediate resist layer. Optical modulation is demonstrated by optical transmission experiments using substrate heating.