Grating-SPR-Self-referenced-IEEE.pdf

This work presents an integrated plasmonic biosensing device consisting of a one-dimensional metallic lamellar grating designed to exploit extraordinary transmission of light toward an underlying silicon photodetector. By means of finite element simulations, the grating parameters have been optimized to maximize the light transmission variation induced by the functionalization of the gold nanostructures. An optimized grating was fabricated using an electron beam process and an optoelectronic test bench suitable for sample tests was developed. A clear difference in the grating transmitted light due to surface functionalization was observed in presence of TM polarized illumination.

2009

We report a compact multi-channel biosensor based on diffraction grating-coupled SPR for the most demanding detection applications in the field or home environments. The sensor utilizes special diffraction grating (referred to as surface plasmon coupler and disperser SPRCD) for coupling light into the surface plasmon and its simultaneous wavelength dispersion through a different diffraction order. This approach combines most of the optical instrumentation on a single SPR chip produced by stamper hot-embossing technique which is fully compatible with mass production. The sensor consists of a disposable cartridge (SPR chip and microfluidics) and a compact SPR instrument with the footprint which includes optical system of SPR sensor, supporting and data acquisition electronics, microfluidics delivering sample into six independent sensing channels in the cartridge, and temperature stabilization. We demonstrate that the sensor is able to measure changes in the refractive index as low as 2x10-7 refractive index units (RIU) and to detect the binding of antibodies to the antigen-coated sensor surface.

IEEE Sensors Journal, 2019

We configure and analyze a nanostructured device that hybridizes grating modes and surface plasmon resonances. The model uses an effective index of refraction that considers the volume fraction of the involved materials, and the propagation depth of the plasmon through the structure. Our geometry is an extruded low-order diffraction grating made of dielectric nano-triangles. Surface plasmon resonances are excited at a metal/dielectric interface, which is separated from the analyte by a high-index dielectric layer. The optical performance of the refractometric sensor is highly competitive in sensitivity and figure of merit (FOM) because of the the ultra-narrow spectral response (below 0.1 nm). Moreover, it is operative within a wide range of the index of refraction (from 1.3 till 1.56), and also works under normal incidence conditions.

Sensors and Actuators B: Chemical, 2012

Surface plasmon resonance platforms based on laser inscribed azo polymer surface relief diffraction gratings were used to detect the binding of organic and biological molecules. Optical sensors were assembled to operate in transmission mode, resulting in a very simple setup. This new approach is observed to present a high sensitivity when compared to other systems, such as SPR-based biosensors using nanoholes. The corrugated surface provides a relatively large surface area and the improved sensitivity to binding events is related to resonant plasmon enhancement on the surface relief grating. It was found that varying the periodicity from 400 to 410 nm does not improve efficiency, however changing the groove depth from 30 to 65 nm, resulted in a twofold increase in sensitivity. An interesting result is that sensors with higher energy surface plasmons present higher sensitivity when compared to lower energy ones. This result can drive further studies toward improved surface plasmon-based sensors.

Applied Optics, 2011

In this study, we investigated the enhanced sensing performance of a localized surface plasmon resonance (LSPR) biosensor by employing metal-dielectric double-layered subwavelength grating structures. The numerical results showed that the LSPR substrate with a dielectric spacer can provide not only a better sensitivity but also a significantly improved reflectance characteristic. While the presence of metallic gratings leads to a broad and shallow reflectance curve inevitably, the dielectric spacer can prevent the propagating surface plasmons from being interfered by the locally enhanced fields excited at the gold gratings, finally resulting in a strong and deep absorption band at resonance. Therefore, the proposed structure could potentially open a new possibility of the enhanced LSPR detection for monitoring biomolecular interactions of low molecular weights.

This paper deals with a new invention of modular surface plasmon resonance (SPR) biosensor device based on wavelength modulation wherein the angle of incidence of the light source is fixed and the shift in wavelength at resonance is monitored. This device is capable of detecting biomolecular binding interactions of different species such as protein and viruses based on changes in the refractive index of the dielectric environment. White light source mounted with a polarizer is used to excite plasmons on the sensor surface which is thin gold film of ~21 µm thickness coated on BK-7 glass. A variable angle reflection sampling system (VARSS) device from Ocean Optics was modified to incorporate the transducer components and sampling accessories. SPR was observed at the angle of incidence of the light fixed at 29°. At this point, plasmon-evanescent wave coupling occurred with highest loss of light intensity observed. Two liquid samples, water (n=1.33) and ethylene glycol (n=1.43) was introduced onto the sensor surface to model changes in wavelength resonance with difference in refractive index of dielectric environment. It was observed that the resonance wavelength for water and ethylene glycol are 590.10 nm and 594.23 nm respectively when reference to air (n=1.00) indicating the workability of the device.

2006

An alternating dielectric multi-layer device was fabricated and tested in the laboratory to show that dielectric mirrors of alternating high/low refractive index materials, based on the design of distributed Bragg reflector (DBR) for vertical cavity surface emission lasers (VCSELs), can be used in designing SPR biochemical sensors. The thickness, number of layers, and other design parameters of the device used were optimized using optical admittance loci analysis. The proof-of-concept device was fabricated with a symmetrical structure using Au/(SiO 2 /TiO 2) 4 /Au. Using a 632 nm-wavelength light source on a BK7 coupling prism, our laboratory tests showed that, under water, there was an 11.5 • shift in resonant peak position towards the critical angle (from 74 • in a conventional single-layer Au film), and a 3.25 times decrease in FWHM (the half-peak width). Our design also resulted in a wider dynamic range of up to a 1.50 refractive index unit (RIU), compared to 1.38 RIU in a conventional single-layer Au film. Using glucose solutions in ddH 2 O, the calculated resolution was 1.28 × 10 −5. The calculated intensity sensitivity was 10 000 a.u./RIU, about twice the improvement over the conventional single-layer Au film.

International Journal of Electronics and Electrical Engineering

A Localized Surface Plasmon Resonance (LSPR) biosensor based on a subwavelength grating structure is studied numerically for detection of bulk refractive change of aqueous environments such as biological buffer solutions. A high grating thickness of 40nm and a short grating period of 50nm are selected to evaluate numerically the effect of the other grating structural parameter i.e. fill factor (f.f) on the sensor performance including dispersion curve, sensitivity, FWHM, MRR and resonance angle. Evaluation shows that corresponding wavelength to the effective resonance of surface plasmons which locating in near infrared (NIR) wavelength range is displaced with f.f value. Also, as shown for some f.f values sensitivity is enhanced slightly whereas FWHM, MRR and resonance angle is increased. Thus with adjusting both of operating wavelength and f.f value, it is possible to get a better performance for the plasmonic sensor.

Biomedical optics express, 2014

A plasmon waveguide resonance (PWR) sensor is designed, fabricated, and tested for self-referenced biosensing. The PWR sensor is able to support two different polarizations, TM and TE. The TM polarization has a large sensitivity to variations in the background refractive index while the TE polarization is more sensitive to the surface properties. The ability of the PWR sensor to simultaneously operate in both TM and TE modes is used to decouple the background index variations (bulk effects) from the changes in adlayer thickness (surface effects) via multimode spectroscopy. To benchmark the performance of the PWR, a conventional surface plasmon resonance (SPR) sensor is fabricated and tested under the same conditions.