The performance of a recently demonstrated silicon nitride slot-waveguide microring resonator biochemical sensor is
analyzed. The slot-waveguide sensor is optically modeled by using finite element method, full-vectorial and semi-vectorial
finite-difference beam propagation methods. Numerical calculations are discussed and compared to the sensor
experimental performance. This study includes homogeneous sensing -by using different aqueous solutions-, surface
sensing -due to both, surface etching and biomolecular layer adhesion-, and power coupling characteristics of the
microring sensor. It is found that all of the aforementioned numerical methods provide good agreement with the
experimental homogeneous sensitivity, surface etching sensitivity and power transmission coefficient at the resonator
coupling. The analysis of the surface sensitivity due to biomolecular layer adhesion suggests biomolecule polymerization
on the surface of the actual device. These results demonstrate the suitability of the proposed numerical optical models
and indicate that the slot-waveguide microring device can be fully wetted with aqueous analytes, which is desirable for
sensing and optofluidic applications at the nanoscale.
A novel ultrasensitive integrated nanomechanical optical sensor is proposed and analyzed. The photonic device consists
of a silicon nitride disk resonator formed by a horizontal slot-waveguide acting as a circular cantilever. The device
sensitivity results from the product of the sensitivities of the slot-waveguide and the disk resonator. A deflection
sensitivity of 11.5 nm-1 is predicted, representing an enhancement of 4 orders of magnitude as compared to state-of-the-art
microcantilever sensors.
We present an approach for systematic high-speed characterization of VCSELs and discuss both its potential benefits and problems. We show how the VCSEL dynamics, under certain conditions, can be well described by a small number of key parameters that can be extracted from measurements and used for further optimization. The calibrated small signal modulation responses of the laser are measured and fitted to an analytical transfer function allowing the estimation of the resonance frequency, damping factor and parasitic cut-off at different bias points. From this data the relative importance of different bandwidth limiting effects due to damping, thermal heating and parasitics can be deducted. We illustrate the approach on 850nm datacom VCSELs using either ion implantation, selective oxidation or semi-insulating regrowth for current confinement. The bandwidth ofthe implanted device appears to be limited by parasitics effects to 3.3GHz. Due to a much smaller injection diameter, the oxidized VCSEL reaches 10GHz, being mainly limited by the high damping. Finally the regrown VCSEL operates up to 5GHz, limited by the parasitics
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