Highly sensitive optical response of optical fiber long period gratings to nanometer-thick ionic self-assembled multilayers

Abstract

Ionic self-assembled multilayers deposited on long period fiber gratings (LPGs) yield dramatic resonant-wavelength shifts, even with nanometer-thick films. Fine control of the refractive index and the thickness of these films was achieved by altering the relative fraction of the anionic and cationic materials combined with layer-by-layer deposition. We demonstrate the feasibility of this highly controllable deposition technique for fine-tuning grating properties. In addition a variety of biological and chemical sensing agents can easily be incorporated into these films, which makes this an attractive platform for realization of high-performance LPG-based sensors.

Fiber-optic coupler based refractive index sensor and its application to biosensing

“…No effects of the flow of a test solution and laser frequency drifts were observed. This sensitivity is comparable to or better than the published sensitivity values for fiber-optic biosensors, [3][4][5][6][7][8] and can be improved by narrowing a peak-tovalley pitch of a coupler sensor. A temperature stabilization system of a test solution or a temperature-drift compensation scheme is essential to measure a refractive index variation less than 10 −4 .…”

“…Label-free sensing is a suitable technology for meeting these requirements in terms of reducing the test reagents consumed and shortening the experimental procedures, and fiber-optic biosensors 1,2 make it possible to realize a small sensing system. Hence, fiber-optic label-free biosensors based on SPR, 3,4 long period grating, 5,6 and Fabry-Pérot interferometer, 7,8 have been developed. These are basically based on measuring a refractive index change due to the binding of biomolecules.…”

Long Period Gratings in New Generation Optical Fibers

“…Moreover, another major pitfall for bare LPGs is their scarce SRI sensitivity in low index ambient (air, water) while they show maximum sensitivity for SRIs close to the cladding RI, typically around 1.45. In this context, a paradigm shift has been represented by the integration of nano-scale polymer overlays with HRI than the cladding and by the discovery of the modal transition phenomenon (Rees et al, 2002;Del Villar et al, 2005;Z. Wang et al 2005;.…”

Lab-on-fiber optofluidic platform for in situ monitoring of drug release from therapeutic eluting polyelectrolyte multilayers

“…At a fundamental level, core mode LP 0,1 to cladding mode LP 0,n coupling takes place when phase-matching condition, λ resonance = (n eff, core -n eff, cladding )Λ, is satisfied [12], where, λ resonance is the coupling resonance wavelength of the cladding mode, n eff, core and n eff, cladding are respective effective indices of the core and the cladding modes, and Λ is grating period. The dependence of λ resonance on n eff, core and n eff, cladding makes SMF-LPG an excellent candidate for sensitive index transduction platform [13][14][15][16][17][18][19][20][21][22][23]. Compared with other techniques such as absorption spectroscopy, electrochemical methods, and mass spectrometry, the LPG has both the sensitivity and ease for in-line systems integration for label free measurement.…”