Dominic Lepage

Surface plasmon assisted photoluminescence in GaAs–AlGaAs quantum well microstructures

Surface plasmon resonance has been investigated in a quantum well (QW) GaAs microstructure the photoluminescence (PL) of which is coupled via a submicrometer period grating with surface plasmons (SPs) propagating at SiO2–Au-dielectric interfaces. Introduction of the SiO2 layer allowed to increase both the propagation length and the penetration depth of SPs and, consequently, achieve their enhanced interaction with the QW PL signal. For a QW GaAs–Al0.5Ga0.5As microstructure emitting at 822nm, a modulated PL emission has been observed in agreement with the calculated resonance conditions expected for such a microstructure and the 375nm period grating.

Plasmonic propagations distances for interferometric surface plasmon resonance biosensing

A surface plasmon resonance (SPR) scheme is proposed in which the local phase modulations of the coupled plasmons can interfere and yield phase-sensitive intensity modulations in the measured signal. The result is an increased traceability of the SPR shifts for biosensing applications. The main system limitation is the propagation distance of the coupled plasmon modes. This aspect is therefore studied for thin film microstructures operating in the visible and near-infrared spectral regions. The surface roughness of the substrate layer is examined for different dielectrics and deposition methods. The Au layer, on which the plasmonic modes are propagating and the biosensing occurs, is also examined. The surface roughness and dielectric values for various deposition rates of very thin Au films are measured. We also investigate an interferometric SPR setup where, due to the power flux transfer between plasmon modes, the specific choice of grating coupler can either decrease or increase the plasmon propagation length.

Hyperspectral imaging of diffracted surface plasmons

We present the results of far field measurements of the complete 3D dispersion relation of a surface plasmon resonance (SPR) effect induced by an integrated quantum well nanodevice. The light modulations in the far field, where the surface plasmons are extracted by a grating, has been calculated for a continuum of energies and wavevectors injected by the luminescent substrate. We introduce a novel experimental method for direct mapping of the EM wave dispersion that enables the monitoring of massive amounts of light-scattering related information. The quasi-real time method is applied for tracking, in the E(k) space, the SPR peak surfaces generated by the investigated nanodevice. Those additional dimensions, measured with scalable tracking precision, reveal anisotropic surficial interactions and provide spectroscopic response for SPR.

Experimental evidence for mobile luminescence center mobility on partial dislocations in 4H-SiC using hyperspectral electroluminescence imaging

We report on the formation, motion, and concentration of localized green emission centers along partial dislocations (PDs) bounding recombination-induced stacking faults (RISFs) in 4H-SiC pin diodes. Electroluminescence imaging depicted the motion of these green emitting point defects during forward bias operation along carbon-core PDs that bound the RISFs. Following high temperature annealing, these green emitting point defects did not contract with the PDs, but remained in the final location during the expansion. This implies that the motion of these green emitting point dislocations is enabled through a recombination-enhanced motion, similar to the process for RISF expansion and contraction within SiC.

Surface plasmon effects induced by uncollimated emission of semiconductor microstructures

We investigate the functioning of an innovative monolithically integrated surface plasmon resonance (SPR) device comprising a metal coated SiO2 layer deposited atop a photoluminescence emitting quantum well (QW) wafer. The device takes advantage of the uncollimated and incoherent emission of QW microstructure. This presents a non-trivial problem in our goal to describe quantitatively the functioning of such a device. We discuss the results of our calculations based on a rigorous coupled-wave analysis algorithm and tensorial approach aimed at the full description of surface plasmons (SPs) coupling in QW semiconductor-based SPR architectures designed for biosensing applications. The results indicate that the injected in-plane wavevectors increase the SPs coupling efficiency up to 103 times in comparison to indirect SPs injection. We discuss the general idea of an experimental setup required for collecting the 3D measurement of SPR dispersion relations hω(kx,ky), potentially enabling a much richer picture of surficial biochemical events. Preliminary results indicate that the proposed methodology produces simultaneously the equivalent of 105 to 108 conventional SPR scans achievable with commercial systems.

Miniaturized Quantum Semiconductor Surface Plasmon Resonance Platform for Detection of Biological Molecules

The concept of a portable, inexpensive and semi-automated biosensing platform, or lab-on-a-chip, is a vision shared by many researchers and venture industries. Under this scope, we have investigated the application of optical emission from quantum well (QW) microstructures for monitoring surface phenomena on gold layers remaining in proximity (<300 nm) with QW microstructures. The uncollimated QW radiation excites surface plasmons (SP) and through the surface plasmon resonance (SPR) effect allows for detection of small perturbation in the density surface adsorbates. The SPR technology is already commonly used for biochemical characterization in pharmaceutical industries, but the reduction of the distance between the SP exciting source and the biosensing platform to a few hundreds of nanometers is an innovative approach enabling us to achieve an ultimate miniaturization of the device. We evaluate the signal quality of this nanophotonic QW-SPR device using hyperspectral-imaging technology, and we compare its performance with that of a standard prism-based commercial system. Two standard biochemical agents are employed for this characterization study: bovine serum albumin and inactivated influenza A virus. With an innovative conical method of SPR data collection, we demonstrate that individually collected SPR scan, each in less than 2.2 s, yield a resolution of the detection at 1.5 × 10−6 RIU.

Integrated electrically driven surface plasmon resonance device for biosensing applications.

Compact and portable surface plasmon resonance (SPR) biosensors of high sensitivities can be made through integration of discrete components in a single device. We report on a device comprising a vertical cavity light emitting diode (VLED) integrated with gold-based biosensing nanostructures fabricated atop its surface. Coupling of surface plasmon waves was achieved by the introduction of a spacer SiO2 layer located between the light source and the functionalized Au thin film. The SPR signal was extracted in far field with a Au-based nanograting and detected using a custom designed hyperspectral imager. We discuss the performance of a VLED-based SPR device employed for detection of different concentration saltwater solutions.