Mechanical tuning of optical race-track ring resonators

This paper presents the fabrication and mechanical characterization of electrostatically actuated micro bimorphs integrated with race-track ring resonators, for optical tuning applications. The bimorphs, having an upward deflection in the off-state, are integrated by surface micromachining techniques with race-track ring resonators fabricated on Silicon On Insulator (SOI) wafers. Using electrostatic actuation, these bimorphs are pulled into the evanescent field of the ring resonator thereby modulating the propagation properties. Pull-in voltages of the bimorphs have been measured statically and the effect of electrostatic spring softening (ESS) on the resonance frequency has been measured dynamically. The resonance wavelength of the optical ring resonator could be tuned by 50 pm by applying an 8.5 V DC voltage to a 40 μm long bimorph, bringing it into close proximity of the ring resonator waveguide. To the best of our knowledge, this is the first experimental demonstration of tuning of race track ring resonators by integrated, electrostatically actuated bimorphs.