In this paper we discuss results obtained with an in-line Fabry-Perot interferometer (FPI) built by splicing a small section of capillary fiber between two pieces of standard single mode fiber, resulting in a rectangular air cavity. The FPIs were characterized regarding sensitivity to temperature and longitudinal strain. The FPIs were bonded to pieces of Terfenol-D, a magnetostrictive alloy, to be used as magnetic field sensors. Fiber Bragg Gratings were also bonded to Terfenol-D for comparison. The FPI based on capillary optical fiber and Terfenol-D showed a higher sensitivity to an applied magnetic field when compared to an FBG.
The viability of a fiber optic reflection-based Localized Surface Plasmon Resonance (LSPR) sensor using layer-by-layer technique composed by PAMAM-AuNP with and without AuNP-citrate was investigated. The PAMAM-AuNPs and PAMAM-AuNPs/AuNP-citrate layers were deposited on the endface of an optical fiber and the reflected signal was acquired. Deposition time and number of layers were optimized viewing LSPR sensing applications. Results with and without AuNP-citrate were compared. The sensor is being characterized as a refractive index sensor.
Previously, we developed an all-fiber reflection Localized Surface Plasmon Resonance (LSPR) sensor based on specular
reflection and LSPR from Au nanoparticles (NPs). The sensor was characterized with standard refractive index fluids.
We now demonstrate that this sensor can be used in chemical sensing applications by using it to monitor the refractive
index of Carbon dioxide (CO2) with refractive index from n=1.04 to n=1.36. In this experiment, the sensor presented a
resolution of approximately 0.02RIU and a sensitivity of at least -45nm/RIU. These results show that the all-fiber
reflection LSPR sensor is a viable method for chemical sensing.
A high sensitivity optical fiber pressure sensor based on a modal interferometer with high birefringence photonic fiber is
proposed and demonstrated. The sensor dependence with hydrostatic pressure is evaluated both numerically and
experimentally. The measured pressure sensitivity at room temperature is found to be 3.36 nmMPa-1.
Thermal poling is an efficient way to induce optical second-order nonlinearity in different types of glasses, which
typically have macroscopic inversion symmetry. In this paper we present a study on the current dynamics during thermal
poling of glasses and relate these results to the formation dynamics of the depletion region, which is closely linked to the
induced optical second order nonlinearity. Based on a simple theoretical viewpoint, supported by experimental results,
we propose that thermal poling of glasses, and space-charge formation in dielectrics in general, can be viewed as an ionic
RC circuit. This, to some extent modified view on thermal poling in glasses, opens up new opportunities to study and
control the depletion layer dynamics subsequently leading to better control of the thermal poling induced optical second
order nonlinearity in glasses.
Two experimental setups, using the fourth harmonic of a Nd:YAG laser (266 nm), for producing Bragg gratings by the external method are described and their results presented and discussed. The two different setups allow the fabrication of gratings of controlled spectral bandwidth (0.3 to 5 nm) with peak position between 1.3 and 1.6 micrometers . The stability of the system and the possibility of writing type IIA gratings are also discussed.
In this work we use a simple and powerful technique (Heat scan) to characterize frequency doubling gratings in fibers. The technique is based on scanning a small heating element along the fiber, thereby affecting the phase relationship of the involved waves in a controlled way. We present recent measurements of the time evolution of the (chi) (2) grating during the preparation process, and discuss aspects of the grating phase.
It is our aim to examine a few aspects of SHG in fibers which have not been sufficiently discussed in the literature, and concentrate our attention on the preparation process under exposure to UV light and to the problem of the phase of the waves involved. We also describe a simple picture which helps in guiding our efforts to understand the process, discussing a few points not noticed and/or not understood earlier.
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