We present the formation of a singularity in k-space from a periodic metal-dielectric nanostructure. The singularity
originates from the balance between alternating normal and anomalous coupling. By employing the formalism of Dirac
dynamics for relativistic quantum particles, we theoretically describe propagation dynamics of surface plasmon
polaritons and demonstrate a strong diffraction anomaly (conical-like diffraction) near the singular point.
A unique all-fiber tunable filter is based on the combination of a single resonant band long period grating (LPG) and an electro-optic polymer second cladding layer. The single resonant band LPG is fabricated by etching the cladding of a standard 125 μm thick fiber and using either ultraviolet (UV) illumination or electric arc discharge to write the grating. Once a single resonant band has been achieved, a polymer second cladding layer is applied to the LPG. The refractive index of the polymer cladding determines the resonant wavelength of the filter and is tuned by applying an external electric field. The grating fabrication method and type of polymer used for the second cladding affect filter performance, and both must be considered when designing an application specific all-fiber filter.
We propose a new mechanism for fiber optic high temperature sensing based on whispering gallery mode resonance in bent optical fibers. Due to the strong whispering gallery mode resonance in cladding-thinned bent optical fibers, long-period grating-like deep spectral peaks are formed in the wavelength domain. The wavelength shift of the resonance peaks as a function of temperature is investigated. It is demonstrated that the single loop of bend ring in the fibers can be used as a transducer for high temperature sensing without any internal structure.
In this paper, a brief review on ultrasensitive fiber optic sensors and their applications, done recently at Penn State, is presented. Our discussions will mainly focus on two types of highly sensitive fiber optic sensors. One type is based on the combination of single resonant band long period gratings (LPGs) with the second refractive index matched polymer cladding layer. The other one is based on the LPGs fabricated in photonic nanostructured fibers and waveguides. It is found that a significantly increased sensitivity (two order plus) can be achieved by harnessing these approaches, which will benefit a variety of applications, in particular, low concentration chemical/biological agents detection.
Highly luminous polymers have been successfully prepared by copolymerization of various arylene vinylene units. Among the copolymers synthesized, poly(phenylene vinylene) (PPV) and its derivatives have been studied most intensively because they show fairly strong fluorescence and have a wide structural variety. In this paper, light-emitting polymers and traditional organic LED technology are briefly reviewed at first. A novel and unique point source based on the organic LED fabricated on an optical fiber is then proposed. As proof of concept, some preliminary experimental results are shown. Two light-emitting materials needed for our experiments are synthesized. It is illustrated that the unique point OLED source is feasible, which can lead to many practical applications, such as biomedical imaging.
In this paper, a brief review of recent advances on high-temperature distributed fiber optic sensors is presented, which includes (1) background on fiber gratings, (2) in-fiber grating fabrication methods in single crystal sapphire fiber, (3) reflection-type fiber specklegram generated in single crystal sapphire fiber, and (4) preliminary experimental results on high temperature sensing.
In this paper, a unique all-fiber tunable filter based on the combination of single resonant band long period grating (LPG) and harsh environment electro-optic polymer second cladding layer is presented. The single resonant band LPG is used to select the resonant wavelength and the tuning of resonant wavelength is realized by changing the refractive index of electro-optic polymer cladding layer via external electric field. Although the basic operational principle and implementation of this unique tunable filter have been previously reported by authors, this paper is focused on athermal operation design and synthesis of harsh environment electro-optic polymer, which enhances the practicability of proposed tunable filter.
In this paper, a unique all-fiber tunable filter based on the combination of single resonant band long period grating (LPG) and harsh environment electro-optic polymer second cladding layer is presented. The single resonant band LPG is used to select the resonant wavelength and the tuning of resonant wavelength is realized by changing the refractive index of electro-optic polymer cladding layer via external electric field. Although the basic operational principle and implementation of this unique tunable filter have been previously reported by authors, this paper is focused on athermal operation design and synthesis of harsh environment electro-optic polymer, which enhances the practicability of proposed tunable filter.
In this paper, a brief review of recent advances on fabricating in-fiber gratings in single crystal sapphire fiber is presented, which includes (1) backgound on fiber gratings, (2) in-fiber grating fabrication methods in single crystal sapphire fiber, (3) the variation of spectral response of sapphire fiber grating induced by the change of ambient refractive index, and (4) reflection-type fiber specklegram generated in single crystal sapphire fiber. The application of this unique fiber grating to harsh environment, high temperature, distributed fiber optic sensor will also be discussed.
In this paper, we propose an innovative extremely harsh environment (up to 2000°C) distributed temperature sensor by fabricating in-fiber gratings in single crystal sapphire fibers. Temperature is sensed by changing grating optical spectral response. By cascading a set of gratings in the same single crystal sapphire fiber, distributed sensing can be achieved. A quantitative analysis on grating design, fabrication, and performance is presented. Some preliminary experimental results are also reported. Application of this unique in-fiber grating to extremely harsh environment temperature sensor will be performed in the near future.
A unique, all-optic switch based on an innovatively designed planar lightwave circuit (PLC) is presented in this paper. The switching function is achieved by using ultra large birefringence of nematic liquid crystals (NLC) filled at the trench of waveguides. The trench at the crossing forms a waveguide mirror or a matching medium when extraordinary and ordinary refractive indices of NLC are employed, respectively. The major advantages of our unique design are: (1) the limitation that refractive index of liquid crystal must be less than that of waveguide material itself is eliminated so that conventional NCL material such as E7 can be used; (2) it is a self aligned fabrication process that alleviates the tight tolerance of later tilt error; (3) the design is thermally stable. The successful fabrication of this unqiue switch could result in an enabling element for the next generation all-optic networks.
In this paper, some recent advances in long period gratings, including (1) widely tunable single resonant band long period gratings, (2) long period gratings fabricated in single crystal sapphire fibers, and (3) long period gratings fabricated in photonic crystal fibers are presented. The applications of these novel long period grating to next generation ultra high capacity optics communication networks, high temperature distributed fiber optic sensors, and highly sensitive biosensors are discussed. Quantitative analyses and preliminary experimental results are provided.
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