Matthew D. Stephens

Direct imaging of transient interference in a single-mode waveguide using near-field scanning optical microscopy

Near-field scanning optical microscopy was used to image transient interference between the guided mode and a leaky mode induced in a single-mode waveguide due to a localized adlayer. The observed field response in the adlayer region as well as the period and decay length of the subsequent interference are in good agreement with beam propagation calculations. The transient interference impacts the element spacing in local evanescent array coupled sensors.

Evanescent field response to immunoassay layer thickness on planar waveguides.

The response of a compact photonic immunoassay biosensor based on a planar waveguide to variation in antigen (C-reactive protein) concentration as well as waveguide ridge height has been investigated. Near-field scanning optical microscope measurements indicate 1.7%nm and 3.3%nm top surface optical intensity modulation due to changes in effective adlayer thickness on waveguides with 16.5 and 10 nm ridge heights, respectively. Beam propagation method simulations are in good agreement with the experimental sensitivities as well as the observation of leaky mode interference both within and after the adlayer region.

Novel local evanescent field detection waveguide multianalyte biosensor

A novel waveguide sensor capable of sensing multiple analytes directly and in real time with label-free, local detection has been investigated. Numerical simulations agree with analytical calculations of the sensor sensitivity. The waveguide parameters including detector to core distance, adlayer length, and surface roughness have been extensively analyzed. Initial experimental realization efforts are summarized.

Characterization of a 90° waveguide bend using near-field scanning optical microscopy

Multiple modes are directly imaged in a silicon nitride waveguide bend using near-field scanning optical microscopy (NSOM). The observations are in good agreement with modal calculations using conformal index transformation.

Initial demonstration of a local, evanescent, array coupled biosensor concept

A concept for a novel, compact, immunoassay biosensor that can simultaneously sense multiple analytes simultaneously is being investigated. The dielectric planar waveguide sensor relies on modulation of the local evanescent field coupled into an array detector. Proof of concept experiments carried out using near-field scanning optical microscopy (NSOM) on a 17 nm thick pseudo-adlayer demonstrated high sensitivity with an optical SNR of approximately 55:1. The measured results agree with numerical simulations

A Waveguide Biosensors Local Evanescent Field Response to an Immunoassay Complex

A compact photonic immunoassay biosensor that can simultaneously sense multiple analytes has been implemented. NSOM results indicate 8% modulation of the local evanescent field due to an 18 nm biological adlayer on the waveguides surface.