We report the first experimental observation of momentum transfer from a surface plasmon to a single dielectric sphere. Using a photonic force microscope, we measure the plasmon radiation forces on different polystyrene beads as a function of their distance from the metal surface. We show that the force magnitude at resonance is strongly enhanced compared to a nonresonant illumination. Measurements performed as a function of the probe particle size indicate that optical manipulation by plasmon fields has a strong potential for optical sorting.
In this paper we demonstrate the first use of enhanced optical forces and optically induced thermophoretic and convective forces produced by surface plasmon polariton excitation for large-scale ordering and trapping of colloidal aggregations. We identify regimes in which each of these forces dominate the colloidal dynamics and lead to different collective equilibrium states. These include accumulation and organization into hexagonal close-packed colloidal crystals, arrangement into linear colloidal particle chains, and the formation of colloids in a ring formation about the excited region.Peer ReviewedPostprint (published version
We report a simple and compact modal interferometer for applications in refractometry. The device consists of a stub of large-mode-area photonic crystal fiber (PCF) spliced between standard single-mode fibers. In the splice regions the voids of the PCF are fully collapsed, thus allowing the coupling and recombination of PCF core and cladding modes. The device is highly stable over time, has low temperature sensitivity, and is suitable for measuring indices in the 1.330-1.440 range. The measure of the refractive index is carried out by monitoring the shift of the interference pattern.
The authors report a highly sensitive (∼2.8pm∕με) wavelength-encoded strain sensor made from a piece of photonic crystal fiber (PCF) spliced to standard fibers. The authors intentionally collapse the PCF air holes over a short region to enlarge the propagating mode of the lead-in fiber which allows the coupling of only two modes in the PCF. The transmission spectrum of the interferometer is stable and sinusoidal over a broad wavelength range. The sensor exhibits linear response to strain over a large measurement range, its temperature sensitivity is very low, and for its interrogation a battery-operated light emitting diode and a miniature spectrometer are sufficient.
The performance of bi-periodic arrays of gold nano-particles for molecular sensing applications is studied using the Fourier Modal Method (FMM). We show that the electromagnetic coupling between the particles can be optimized to increase their sensitivity to a weak change of the shallow dielectric environment. Especially, arrays whose elementary cell consists of a dimer of two closely packed particles are found to be at least three times more sensitive than single particle arrays.
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