A novel structure of the intrinsic Fabry-Perot interference (IFPI) fiber temperature sensor is presented. The sensor uses two different core diameter fibers and produces a reflective mirror by fusing uncoated bare fibers. This procedure not only solves the problem of controlling thickness and reflectance of the thin film but also provides easier and cheaper technologies for IFPI fiber sensors. Theoretical and experimental aspects of the intrinsic Fabry-Perot cavity are described. Both theoretical and experimental results from this novel structure show good agreement with those from the traditional Fabry-Perot fiber sensor.

A novel structure for the intrinsic Fabry-Perot fiber-optic temperature sensor

We propose a new approach to solve the problem of the propagation of electromagnetic waves in unidimensional media with an arbitrary variation of their dielectric permittivity. This method is deduced from the Maxwell equations with a minimum of approximations and allows a full vectorial description of both the electric and magnetic fields through the direct calculation of their Cartesian coordinates. The problem is then equivalent to the solution of a pair of uncoupled ordinary differential equations. We use a very intuitive, highly accurate, pseudospectral technique to solve these equations. This pseudospectral method is based in a combination of Fourier and polynomial expansions of the solution providing very good precision and excellent stability with a relatively low computational effort. We present a simple model of a photonic crystal as an example of application of this technique to real electromagnetic problems.

/pdf/rigorous-full-vectorial-analysis-of-electromagnetic-wave-3znav2w6pu.pdf

Rigorous Full Vectorial Analysis of Electromagnetic Wave Propagation in 1D

A new trial function is proposed to obtain the propagation constant, the normalized group delay, and the modal dispersion parameter of single-mode graded-core W-type fibers. This function uses only simple elementary functions to approximate the fundamental modal fields. In many cases of study, we show that the present trial function gives a significant improvement over the existing trial functions and is very useful in the analysis of fibers and related devices.

Variational analysis of single-mode graded-core W-fibers

Approximate method for chromatic dispersion estimation of the high-order guided modes, propagating along the core of
the weakly guiding single-cladding optical fiber with an arbitrary graded refractive index profile, is represented. Proposed
method is based on the modified Gaussian approximation, and does not require to equate and find solutions of the
simultaneous integro-differential equations. By applying presented method, chromatic dispersion curves both for the
fundamental and high-order modes were obtained, and compared with exact solutions, corresponding to ideal step index
and non-limited parabolic profiles. In all cases, good accuracy was noticed.

Method for chromatic dispersion estimation of high-order guided modes in graded index single-cladding fibers

The fabrication of polymeric single-mode Gaussian profile optical waveguides is described. We used poly(methyl methacrylate) and a mixture of two intermiscible monomers for the cladding and the core, respectively, of the waveguides. The cores of the waveguides were fabricated by with an argon-ion laser beam. The waveguides had single-mode Gaussian refractive-index profiles. By using such waveguides, we fabricated directional couplers for power coupling to the adjacent waveguides and also parallel waveguide arrays for preventing power coupling to adjacent waveguides for use in interconnect chips. We analyzed the characteristics of these couplers by using the coupled-mode theory and compared the results with those obtained with the beam propagation method. Experimental results showed good correlation with the theoretical values. We designed optical bus arrays for interconnect chips, considering the variation of normalized frequency V, the power penalty, and the dimensions of the waveguides and the separation between them. The number of waveguides in the bus array increased with increasing V. For a known value of V, a waveguide's density increases with a decrease of its dimensions. The theoretical maximum number of waveguides is ~1490/cm and ~846/cm for 2 mum x 2 mum and 4 mum x 4 mum single-mode waveguides, respectively, to satisfy a 1-dB power penalty criterion at bit-error rate of 10(-9). We fabricated interconnect bus arrays with fifteen 4 mum x 4 mum waveguides for a 3-cm coupling length, and the experimental results were verified to be in good agreement with the theoretical values.

Characteristics of polymeric optical passive single-mode waveguiding devices fabricated by an argon-ion laser

A new trial function which extends the generalized Gaussian method for the study of weakly guiding single-mode fibers is presented. This function uses only simple elementary functions to approximate the fundamental modal fields. In many cases of study, we show that the present trial function gives a significant improvement over the existing trial functions, and it is very useful in the analysis of fibers and related devices. >

Extended Gaussian approximation for single-mode graded-index fibers

Some trial fields are proposed for obtaining the propagation characteristics of single-mode inhomogenous planar waveguides, based on the scalar variational principle. A comparison with other trial fields and the exact numerical results shows that the authors' results are more accurate than those obtained by the existing trial fields. The proposed trial fields also agree favorably with the real inhomogeneous index profiles. >

Variational analysis of single-mode inhomogeneous planar optical waveguide

Some new trial functions that extend the Hermite-Gaussian (HG) function are proposed for solving the modal coupling of one planar graded-index waveguide region to another and with the assumption of no reflections, based on the scalar variational principle. In many cases in this work, we show that the present trial functions give a significant improvement over the HG trial function and are very close to the exact numerical results. Since approximate results in a closed form can be derived by variational approach, this analysis is also very useful in the modal-coupling design of the other integrated-optical devices. >

Variational analysis of modal-coupling efficiency between graded-index waveguides

Narrow-band and low-sidelobe all-fiber spectral filters are achievable with directional couplers constructed with W-index and step-index fibers. The sidelobe levels can be reduced significantly by properly weighting the coupling strength along the device. We provide numerical simulations in which the different weighting functions are obtained via a variable intercore separation. With a Gaussian function weighting, -38 dB transfer response sidelobes have been obtained, which is more than 29 dB reduction over the uniform coupling case. Some design rules for obtaining filters with desired bandwidths and coupling lengths are also given. These results can be very useful in the design of high-performance all-fiber filters for wavelength multiplexing. >

Design of high-performance all-fiber spectral filter with weighted coupling

Commercial 316L SS, CoCrMo, and Ti6Al4V alloys have been widely used as implant materials for biomedical applications. However, the inadequate wear resistance and the released metal ions could result in inflammation, cytotoxicity, and shorten the lifespan of surgical implants. To extend the service life and durability of metallic biomaterials, the TiNbTaZrMoV HEA was developed by integrating biocompatibility characteristics with the unique properties of high-entropy alloys (HEAs). Both as-cast TiNbTaZrMo and TiNbTaZrMoV HEAs consisted of dual BCC phases in the dendritic structure: the dendrite region was enriched with Ta, Mo, and Nb, while Zr, Ti, and V were concentrated in the interdendrite region. The homogenized TiNbTaZrMoV HEA possessed a single BCC phase with a homogeneous component distribution. Moreover, the wear resistance of the homogenized TiNbTaZrMoV HEA was superior to the as-cast TiNbTaZrMo and TiNbTaZrMoV HEAs. In terms of electrochemical behaviors, the homogenized TiNbTaZrMoV HEA exhibited superior corrosion resistance compared to the other commercial metallic biomaterials in phosphate-buffered saline solution at 37 °C. The in vitro biocompatibility evaluation revealed that the homogenized TiNbTaZrMoV HEA could support the attachment and proliferation of the MC3T3-E1 cells, presenting good biocompatibility comparable to the Ti6Al4V alloy. This study demonstrated the feasibility of the homogenized TiNbTaZrMoV HEA for orthopedic bioimplant applications. 

Shih-Chieh Chao

Papers

Extended Gaussian approximation for single-mode graded-index fibers

Variational analysis of single-mode inhomogeneous planar optical waveguide

Variational analysis of modal-coupling efficiency between graded-index waveguides

Design of high-performance all-fiber spectral filter with weighted coupling

Biocompatible As-cast and Homogenized TiNbTaZrMoV High Entropy Alloys: Mechanical Properties, Corrosion Resistance and In Vitro Studies