Donato Luna-Moreno

Optical-fiber surface-plasmon resonance sensor with multiple resonance peaks

We report on an optical fiber surface plasmon resonance sensor that exhibits multiple resonance peaks. The sensor is based on a uniform-waist single-mode tapered fiber coated on one side with a thin metal layer. Owing to the asymmetry of the sensor structure, the different hybrid surface plasmon modes supported by the semicircular layer can be excited by the fundamental fiber mode. As a result, the sensor transmission spectrum exhibits several dips that depend on the taper waist diameter. The advantages of a plasmon resonance sensor with multiple dips are discussed.

Refractive index measurement of pure and Er3+-doped ZrO2–SiO2 sol–gel film by using the Brewster angle technique

Abstract The application of the Brewster angle technique and a genetic algorithm for the measurements of refractive index and thickness in tetragonal ZrO 2 :Er 3+ and ZrO 2 –SiO 2 films prepared by the sol–gel process and dip–coating technique annealed at 550°C are reported. A precision higher than 99.5% and 98% in the refractive index and thickness measurements were obtained, respectively. Analysis of the capability to tune the refractive index of high-density blend films by changing the molar concentration of zirconium dioxide, with an increment rate of (0.0052±0.0004)/mol, are also presented.

In-line optical fiber sensors based on cladded multimode tapered fibers

The use of uniform-waist cladded multimode tapered optical fibers is demonstrated for evanescent wave spectroscopy and sensors. The tapering is a simple, low-loss process and consists of stretching the fiber while it is being heated with an oscillating flame torch. As examples, a refractive-index sensor and a hydrogen sensor are demonstrated by use of a conventional graded-index multimode optical fiber. Also, absorbance spectra are measured while the tapers are immersed in an absorbing liquid. It is found experimentally that the uniform waist is the part of the taper that contributes most to the sensor sensitivity. The taper waist diameter may also be used to adjust the sensor dynamic range.

In-line tunable band-edge filter based on a single-mode tapered fiber coated with a dispersive material

We report the use of a single-mode tapered fiber coated with a dispersive material as a tunable band-edge filter. The band-edge wavelength can be adjusted, over a range of /spl sim/500 nm (1150-1650 nm), in a simple way with the taper waist diameter, the interaction length, or with the refractive index of the dispersive material that coats the taper. Moreover, the fabrication procedure is simple and of low cost.

Contrast enhancement of optical coherence tomography images using branched gold nanoparticles

We propose the use of branched gold nanoparticles (B-GNPs) as a contrast agent for optical coherence tomography (OCT) imaging. Our results show that even when the central source of our OCT (1325 nm) is too far from the maximum peak of the plasmon resonance, branched nanoparticles scatter light very efficiently at this wavelength. B-GNPs were tested as a contrast agent in water and agarose-TiO2 tissue phantoms; the estimated increments in contrast were 9.19 dB and 15.07 dB for branched nanoparticles in water with concentrations of 2.2 × 109 NPs/mL and 6.6 × 109 NPs/mL, respectively, while for agarose-TiO2 tissue phantoms the estimated value was 3.17 dB. These results show the promising application of B-GNPs as a contrast agent for tissue imaging using OCT, not only for sources at 1325nm but also at other central wavelengths located between 800 and 1000 nm.

Study on the feasibility of a dry color printing process

A new color printing process is based on the photodissociation of spiropyran complexes accelerated by electron transfer with an organic semiconductor. Good quality prints were obtained using an optimum composition with complexes from three different spiropyrans and variable concentration.

Determination of quality and adulteration of tequila through the use of surface plasmon resonance.

In this work, the surface plasmon resonance (SPR) technique is used to determine the quality or adulteration of tequila beverages. Graphic analyses of the position and width of the SPR curve are related to the complex refractive index of the sample, showing differentiated regions where one can easily and unambiguously identify white, aged, or extra-aged tequilas, and even adulterated or low quality tequilas. The curves generated by aged and extra-aged tequilas, with respect to those obtained from white tequilas, are wider, while the resonant peak shifts towards larger angles. This behavior should be attributed to the aging process. The resonance curve is generated in 20 s, minimizing the variations of the SPR curve parameters due to temperature fluctuations.

Rosin with bromophenol blue® dye as holographic material

Abstract Bromophenol blue ® (BPB) dyed with the rosin and isopropyl alcohol produces a film with a uniform yellow appearance, which can be deposited on glass plates by simple technique. This mixture shows good photosensitivity in the blue light ( λ =457 nm line) employing argon-ion laser and presents high resolution for holographic application. Consequently, it is possible to obtain holographic elements, e.g., gratings.

Detection of aromatic compounds in tequila through the use of surface plasmon resonance.

For an expert nose, the aroma of a beverage is a fingerprint that can be used to certify its authenticity, distinguish between distillation processes, or even identify the raw material used to fabricate it. In this work, we propose a simple, automatic, and repeatable optical method, which can be used as a first and quick test to authenticate tequila samples. This method is based on the measurement of beam intensity changes, using the surface plasmon resonance technique, operating at a fixed angle. We observed that each tequila, depending on the alcohol content and aging process, produces a specific change in measured intensity level.

All-optical switching with fast-response variable-index materials

A high-speed all-optical switch using a fiber optic coupler and a light-sensitive variable-index material is described. The mechanism of index variation with light is discussed, as well as the results of switching with polydialkylsilane and polythiophene for index modulation.