The investigation of the behavior of a long period grating sensor with a copper sensitive coating fabricated by layer-by-layer electrostatic adsorption

Fiber optic long period grating sensors with a nanoassembled mesoporous film of SiO_2 nanoparticles

“…Several approaches for depositing coatings of sub-µm thickness onto the surface of LPGs have been examined, such as Langmuir-Blodgett (LB) [4], electrostatic self-assembly (ESA) [5], layer-by-layer (LbL) and dip-coating [2,3] techniques. Such surface modification has enabled sensitive and selective measurements, with reports of demonstrations of specific optical sensors for pH, humidity, and chemical and biological components [8][9][10][11][12][13][14]. The sensitivity of the LPG's resonance bands to changes in the optical properties of the deposited film is largest when the optical thickness of the coating (product of the physical thickness and refractive index) is of the order 300 nm [8].…”

Response of fiber-optic long-period gratings operating near the phase-matching turning point to the deposition of nanostructured coatings

“…It has been shown that the transmission spectrum of an LPG exhibits a high sensitivity to the optical properties of coatings of materials of refractive index higher than that of the cladding when the coating is of thickness of order 200 nm [7,8,9]. This sensitivity has been exploited to demonstrate a range of chemical sensors, for example, pH [10], copper [11] and DNA damaging agents [12]. To date, the studies of the response of LPG transmission spectra to the deposition of nanostructured coatings has focussed on resonance bands corresponding to coupling to the lower order cladding modes, operating at wavelengths below their dispersion turning point.…”

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.…”