Magnetically tunable surface plasmon resonance based on a composite consisting of noble metal nanoparticles and a ferromagnetic thin film

An FBG magnetic sensor for oil flow monitoring in sandstone core

Monitoring the oil movement using a non-contact optical fiber probe during enhanced oil recovery is a novel technique to increase the efficiency of the process by distinguishing the oil position in the reservoir. A partially unclad fiber Bragg grating (FBG) coated with Fe₃O₄ nanoparticles as a magnetic field sensor is experimentally demonstrated. A series of six FBGs reflecting different wavelengths are fixed on the surface of sandstone. Nanofluids containing magnetite nanoparticles and alkaline-surfactant-polymer are injected continuously in two separate steps into the sandstone, which is saturated with 20% oil and 80% brine. The chamber is equipped with a solenoid that acts as a magnetic field generator. The changes in the magnetic field strength depended on the FBG-solenoid distance and the density of localized injected nanoparticles near the FBGs leads to a shift of the reflected wavelength of each single FBG accordingly. The shift is caused by the interference of different propagating modes reflected from the core-cladding and cladding-magnetite layer interfaces. The intensity of the FBG spectra decreases by injecting the nanofluid and vice versa for surfactant injection. The sensor response time of ∼21 s confirms the high reliability and repeatability of the sensing scheme. Movement of oil along the sandstone alters the wavelength shift in the FBG spectra.

Monitoring the oil movement using a non-contact optical fiber probe during enhanced oil recovery is a novel technique to increase the efficiency of the process by distinguishing the oil position in the reservoir.

Magnetic field modulation of photonic bandgap on FeCo/NiO half-shell array

FeCo/NiO half-shell arrays were fabricated based on the periodic monolayer polystyrene spheres. The two-dimensional magnetic periodic arrays form well-defined photonic crystals with pronounced stop bands. Quite interestingly, it is found that the stop bands can be tuned by an external magnetic field. The underlying mechanism is attributed to the controllable dielectric constant of the magnetic FeCo film under an applied magnetic field. The results shown here may open up an avenue for magnetically tunable photonic crystal stop bands, which may be useful for the creation of new magneto-optical devices.