L.J. Kauppinen

Tuning a racetrack ring resonator by an integrated dielectric MEMS cantilever

The principle, fabrication and characterization of a dielectric MEMS cantilever located a few 100 nm above a racetrack ring resonator are presented. After fabrication of the resonators on silicon-on-insulator (SOI) wafers in a foundry process, the cantilevers were integrated by surface micromachining techniques. Off-state deflections of the cantilevers have been optimized to appropriately position them near the evanescent field of the resonator. Using electrostatic actuation, moving the cantilevers into this evanescent field, the propagation properties of the ring waveguide are modulated. We demonstrate 122 pm tuning of the resonance wavelength of the optical ring resonator (in the optical C-band) without change of the optical quality factor, on application of 9 V to a 40 µm long cantilever. This compact integrated device can be used for tuning/switching a specific wavelength, with very little energy for operation and negligible cross talk with surrounding devices.

Micromechanically tuned ring resonator in silicon on insulator

Monolithic integration of a micromechanical cantilever with an optical ring resonator in silicon on insulator is demonstrated. The ring is tuned over a 120 pm wavelength range by applying 9 V, without affecting its Q-factor.

Optimisation study of micro cantilevers for switching of photonic band gap crystals

We propose to use electrostatically actuated micro bimorph cantilevers with tips for nanometric perturbations in the evanescent field of various resonators and photonic band gap crystals (PBG) using a self aligning technology. Since in PBG and in other high optical index contrast structures the interaction of evanescent field with mechanical elements start to play a role typically with a distance <400 nanometers, the required cantilever strokes for switching c an be accordingly small. This allows for fabrication of relative stiff cantilevers with resonance frequencies in the MHz range. In this contribution we describe the technology for such devices, the optimization studies of the cantilever designs and measurements of mechano-optical interactions using an AFM based cantilever.

Mechano-optical wavelength tuning in a photonic crystal microcavity with sub-1 V drive voltage.

A micro-bimorph cantilever with self-aligned nanotips is monolithically integrated with a photonic crystal based device using optical and deep UV lithography techniques. Upon electrostatic actuation, the dielectric nanotips perturb the optical field, providing electromechano-optical modulation of light. Static tuning of the optical transmission spectra by more than 600 pm is measured with a sub-1 V drive voltage, resulting in a modulation as high as 21 dB. The observed strong electromechano-optical effect may find application in power efficient devices for optical communication networks, such as wavelength routing elements.

Focused ion beam milled on-chip resonator nanostructures for applications in rare-earth-ion-doped Al 2 O 3 active waveguides

Reflection gratings on Al2O3 channel waveguides were defined by focused ion beam milling. Fabry-Perot microcavities were fabricated and improved performance upon annealing was demonstrated, making them viable candidates as resonators for on-chip waveguide lasers.

Proceedings of the First International Workshop on FIB for Photonics : Eindhoven, the Netherlands, 13-14 June 2008: collocated with the 14th European Conference on Integrated Optics (ECIO 2008)

We report our recent results on an optimization study of focused ion beam (FIB) nano-structuring of Bragg gratings in

On-chip bulk-index concentration and direct, label-free protein sensing utilizing an optical grated-waveguide cavity

Al_2O_3

Fabrication of integrated bimorphs with self aligned tips for optical switching in 2-D photonic crystal waveguides

channel waveguides. By optimizing FIB milling parameters such as ion current, dwell time, loop repetitions, scanning strategy, and applying a top metal layer for reducing charging effects and improving sidewall definition, reflection gratings with smooth and uniform sidewalls were achieved.Focused ion beam (FIB) milling can be used as a tool to fabricate structures with sub-micrometer details. The slab material can be silicon, for example, which can then be used as a mould for nano-imprint lithography, or in silicon on insulator (SOI) layer configuration suitable for photonic applications. In the latter, additional effort has to be taken to prevent high FIB induced losses, due to ion implantation and material crystal damage. Perfectly vertical sidewalls are, in principle, required for photonic crystal applications to guarantee low-loss propagation; sidewall angles of 5 degrees can already induce a 8 dB/mm propagation loss. We report on optimization of the sidewall angle (FIB) fabricated submicron diameter holes. Our best case results show that sidewall angles as small as 1.5 degree are possible in Si membranes and 5 degree for (bulk) Si and SOI by applying larger doses and using a spiral scan method.