title: Analysis of silicon-on-insulator slot waveguide ring resonators targeting high Q-factors.
abstract: Vertical slot waveguide micro-ring resonators in silicon photonics have already been demonstrated in previous works and applied to several schemes, including sensing and hybrid nonlinear optics. Their performances, first quantified by the reachable Q-factors, are still perceived to be restrained by larger intrinsic propagation losses than those suffered by simple Si wire waveguides. In this Letter, the optical loss mechanisms of slot waveguide micro-ring resonators are thoroughly investigated with a special focus on the coupler loss contribution that turns out to be the key obstacle to achieving high Q-factors. By engineering the coupler design, slotted ring resonators with a 50 μm radius are experienced with a loaded Q-factor up to 10 times improvement from Q=3,000 to Q=30,600. The intrinsic losses due to the light propagation in the bent slot ring itself are proved to be as low as 1.32±0.87  dB/cm at λ=1,550  nm. These investigations of slot ring resonators open high performance potentials for on-chip nonlinear optical processing or sensing in hybrid silicon photonics.
authors.forename: Weiwei
authors.initials: W
authors.lastname: Zhang
authors.forename: Samuel
authors.initials: S
authors.lastname: Serna
authors.forename: Xavier
authors.initials: X
authors.lastname: Le Roux
authors.forename: Carlos
authors.initials: C
authors.lastname: Alonso-Ramos
authors.forename: Laurent
authors.initials: L
authors.lastname: Vivien
authors.forename: Eric
authors.initials: E
authors.lastname: Cassan