High resolution interrogation of tilted fiber grating SPR sensors from polarization properties measurement

Abstract

The generation of surface plasmon resonances (SPRs) in gold-coated weakly tilted fiber Bragg gratings (TFBGs) strongly depends on the state of polarization of the core guided light. Recently, it was demonstrated that rotating the linear state of polarization of the guided light by 90° with respect to the grating tilt allows to turn the SPR on and off. In this work, we measure the Jones matrix associated to the TFBG transmission properties in order to be able to analyze different polarization-related parameters (i.e. dependency on wavelength of polarization dependent loss and first Stokes parameter). As they contain the information about the SPR, they can be used as a robust and accurate demodulation technique for refractometry purposes. Unlike other methods reported so far, a tight control of the input state of polarization is not required. The maximum error on refractive index measurement has been determined to be ~1 10(-5) refractive index unit (RIU), 5 times better than intensity-based measurements on the same sensors.

Light Polarization-Assisted Sensing with Tilted Fiber Bragg Gratings

“…An unambiguous SPR signature appears in the TFBG amplitude spectrum, as reported in [11,12]. It is strongly sensitive to surrounding refractive index (SRI) changes [12][13][14][15], which yields an implementation of SPRbased (bio-)sensors easy to fabricate and to use.…”

“…It was also demonstrated recently that the differential behavior between two orthogonally polarized TFBG transmitted spectra can be used for demodulation purposes. We showed that narrowband resonant features (also located at wavelengths just below the SPR center) present a wavelength shift that enables refractive index measurements with a resolution better than 10 -5 RIU, achieved through a quality factor of 10 5 and signal-tonoise ratio greater than 50 dB [13,14]. This particular finding was supported by a recent theoretical analysis that showed how the presence of the gold layer shields azimuthally polarized cladding modes from the outside environment while allowing radially polarized ones to tunnel through and excite Plasmons [15].…”

“…The crossing point occurs for the 0 mode -so-called "apolarized" resonance -because it has the same effective refractive index for all the polarization states. This resonance is also characterized by the minimum PDL since it is defined as the absolute value of the difference between the S and P modes [13]. To the right of the 0 mode, the P resonances appear on the short wavelength side of the S ones.…”

EDC-Mediated Oligonucleotide Immobilization on a Long Period Grating Optical Biosensor

“…The most important advantages of this biosensor platform are that it is able to provide biosensing with unique features of label-free, real-time, multiplex, and in-line determination. Various fiber optic biosensors have been presented by employing long period gratings (LPGs) [7,8], tilted fiber gratings (TFGs) [9][10][11] micro fiber Bragg gratings (mFBGs) [12] LPGs in photonic crystal fibers [13] and surface plasmon resonance (SPR) [14].…”

Fabry–Pérot-based surface plasmon resonance sensors

“…The structures of the other types are complex, and hence they have not been widely used, although their ability to offer higher sensitivities has been demonstrated [8,9]. Recently, in order to improve the sensitivity and practicality of SPR sensors and extend their applications, many research works have been focused on devising new configurations and mechanisms while retaining the simplicity of conventional SPR sensors [10,11]. Among them, plasmonic cavities have generally been used to enhance the sensitivity of the SPR sensors [12,13].…”