Interferometric-type optical biosensor based on exposed core microstructured optical fiber

Abstract

In all cases accepted manuscripts should:  link to the formal publication via its DOI  bear a CC-BY-NC-ND license -this is easy to do, click here to find out how  if aggregated with other manuscripts, for example in a repository or other site, be shared in alignment with our hosting policy  not be added to or enhanced in any way to appear more like, or to substitute for, the published journal article Abstract: This work presents a novel biosensor using the multimode interference effect in an exposed core microstructured optical fiber (ECF). In this work biotin molecules are immobilized onto the ECF core surface to serve as the capturing probe for streptavidin, the target molecules.Since each distinct guided mode in the ECF interacts with the surrounding medium differently, the interference between any two specific modes will experience a fringe shift (or phase change) upon a change in the refractive index (RI) of the surrounding medium, or a localized RI change on the surface of the ECF core as a result of a biological binding event. In our experiment, the interferometric sensing platform was realized by splicing a section of ECF with lead-in and leadout single mode fibers (SMFs). An interference pattern is obtained in the transmission spectrum as the result of multiple excited modes (excited and re-collected at the lead-in and lead-out splicing points) propagating in the ECF with different propagation constants. The interference pattern is non-uniform, indicating that there are more than two modes involved. Fast Fourier transform (FFT) is used to separate individual interference patterns that contribute to this complex spectrum and monitor their phase changes upon RI variation of the surrounding medium. In this way multiple RI sensitivities can be realized because each spatial frequency possesses a distinct sensitivity with respect to the surrounding RI. The operation of this device was validated by measuring the phase changes that occur when the sensing platform was subjected to solutions of different RIs or functionalized with different molecules. A biosensor was demonstrated based on this novel platform using biotin as the capturing probe to detect streptavidin with low non-specific adsorption. The proposed platform is reliable, cost-effective, and offers a potential label-free biosensing alternative to the widely used surface plasmon resonance (SPR) technique.

Simultaneous Measurement of Temperature and Refractive Index Using an Exposed Core Microstructured Optical Fiber

“…FFT techniques are widely used for de-multiplexing interference spectra [25,26], which is more precise than other methods of tracking interference spectrum shifts, such as peak tracking or function fitting [27]. The value of the phase () is taken from the complex value at the FFT peak.…”

“…While it is in principle possible to measure both parameters simultaneously using the higher order mode FBG reflections, the sensor had relatively poor sensitivity to RI the order of only 1-5 nm/RIU [1,24]. We have since shown that interferometric based exposed-core fiber sensors can offer high RI sensitivity [25,26], such as 667 nm/RIU in a multimode Mach-Zehnder configuration [25].…”

Quantum noise limited nanoparticle detection with exposed-core fiber

“…The region where the evanescent field propagates determines the interaction volume between the light and the surrounding medium. This accessible interaction volume allowed a wide variety of applications including sensors for biology [18,19]. For example, exposed-core fibers have been used for the detection of fluorescence signals [20,21] and for detection of label-free molecule ensembles in an interferometric configuration [18,19].…”

Direct core structuring of microstructured optical fibers using focused ion beam milling

“…Demonstrated sensing configurations and applications are diverse, including: hydrogen peroxide sensing using Raman scattering [19], fluorescent indicator coatings for detection of aluminum [20] and calcium and cadmium ions [21], absorption spectroscopy of biomolecules [22], and the use of fluorescent labeling techniques for antibodies [23] and proteins [24]. There are also numerous examples of microstructured optical fiber sensing techniques that measure changes in the refractive index of the material filled into the fiber holes [14], such as: techniques based on multimode interferometry [25], multi-core mode-coupling [26], and surface plasmon resonance [27][28][29][30].…”