Differential Sensing with Replicated Plasmonic Gratings Interrogated in the Optical Switch Configuration

Abstract

A new plasmonic configuration is proposed for application in a sensor and demonstrated for the detection of variations in the bulk refractive index of solutions. The configuration consists of monitoring two diffracted orders resulting from the interaction of a TM-polarized optical beam incident on a grating coupler, operating based on an effect termed the “optical switch”. The two monitored diffracted orders enable differential measurements which cancel the drift and perturbations common to both, leading to an improved detection limit, as demonstrated experimentally. The measured switch pattern associated with the grating coupler is in good agreement with theory. Bulk sensing is demonstrated under intensity interrogation via the sequential injection of solutions comprised of glycerol in water into a fluidic cell. A limit of detection of about 10−6 RIU was achieved. The optical switch configuration is easy to implement and is cost-effective, yielding a highly promising approach for the sensing and the real-time detection of biological species.

SPR sensor based on switch effect for very low hydrogen detection

“…Then, in this configuration with 120 nm gold layer thickness, the sample is a refractive index sensor. Bruhier et al 7 found a detection limit on the refractive index of 2x10 -7 RIU, while E. Laffont et al 8 found a detection limit of 10 -6 RIU with their transducers in the switch configuration. Then, standards of 10 -6 RIU were fixed on our sample to validate their quality.…”

Development of a new plasmonic transducer for the detection of biological species

“…n i and k 0 respectively represent the RI of the sensing medium and the wavenumber of the incident beam. This figure is extracted from [149]. Reprinted with permission from https://doi.org/10.3390/s23031188.…”

“…A DAQ (data acquisition) device (8) and a computer (9) were used to record the measurements. This figure is extracted from[149]. Reprinted with permission from https://doi.org/10.3390/s23031188.…”

“…The solutions were injected through this flow cell by polyetheretherketone (peek) tubings (inlet and outlet), which were fixed to needles of syringes controlled by a pump (11 pico plus elite single syringe) from Harvard Apparatus.A rotation stage holding the flow cell was used to set the angle of incidence at one of the working points, as shown in Figure4.3. As described in our article[149], "the grating inside the flow cell was aligned along the central rotation axis via an xy stage", as shown in Figure4.3. "Both 0 th and −1 st orders power were collected by two 5 × 5 mm² Si-based photodiodes, which were fixed to tracks connected to two other rotation stages with their axes of rotation aligned with those of the rotational stage controlling the cell orientation.…”

Performance of Grating Couplers Used in the Optical Switch Configuration

“…This effect involves a transfer of energy between two orders diffracted by a deep sinusoidal metallic grating, as the angle of incidence is varied over a few degrees about a specific angle of incidence, where the power in both diffracted orders is equal. Sensing based on this effect was demonstrated for the first time by detecting small changes in the bulk refractive index of aqueous [23] and gaseous media [24] with very good performance (in the range of 10 −6 -10 −7 RIU) in terms of limit of detection (LOD). The main advantages of this configuration include the ability to perform differential measurements in real time using a simple interrogation setup and the ability to fabricate the grating couplers cost-effectively.…”