Annamaria Cucinotta

Complex FEM modal solver of optical waveguides with PML boundary conditions

A full-wave modal analysis of two-dimensional, lossy and anisotropic optical waveguides using the finite element method (FEM) is presented. In order to describe the behavior of radiating fields, anisotropic perfectly matched layer boundary conditions are applied for the first time in modal solvers. The approach has been implemented using high order edge elements. The resulting sparse eigenvalue algebraic problem is solved through the Arnoldi method. Application to an antiresonant reflecting optical waveguide is reported.

Tailoring of flattened dispersion in highly nonlinear photonic crystal fibers

The dispersion properties of large-hole photonic crystal fibers (PCFs) are tailored by changing the diameter of the air-holes belonging to the first three rings, in order to obtain fibers with a small effective area and low dispersion values in a wide wavelength range around 1550 nm. Highly nonlinear triangular PCFs with effective area of a few square micrometers, flattened dispersion curve, and zero-dispersion wavelength around 1500 nm have been designed.

Leakage properties of photonic crystal fibers

An analysis of the con.nement losses in photonic crystal fibers due to the finite numbers of air holes is performed by means of the finite element method. The high flexibility of the numerical method allows us to consider fibers with regular lattices, like the triangular and the honeycomb ones, and circular holes, but also fibers with more complicated cross sections like the cobweb fiber. Numerical results show that by increasing the number of air hole rings the attenuation constant decreases. This dependence is very strong for triangular and cobweb fibers, whereas it is very weak for the honeycomb one.

Dispersion properties of square-lattice photonic crystal fibers

In this paper the guiding properties of photonic crystal fibers with a square lattice of air-holes in a silica matrix have been studied for the first time. The dispersion curves of fibers with different hole-to-hole spacing and air-hole diameter have been accurately calculated. Negative values of the dispersion parameter and the dispersion slope have been obtained with a hole-to-hole spacing of 1 microm. A comparison between fibers with square and triangular lattice has been also performed, taking into account the dispersion properties and the effective area in the wavelength range between 1200 nm and 1600 nm.

Characterization of microstructured optical fibers for wideband dispersion compensation

Microstructured optical fibers (MOFs) with small hole-to-hole spacing and large airholes are designed to compensate the anomalous dispersion and the dispersion slope of single-mode fibers. The geometrical parameters that characterize triangular MOFs are chosen to optimize the fiber length and the compensation over a wide wavelength range. A proper design of the photonic crystal fiber geometry allows us to achieve dispersion values of approximately -1700 ps nm(-1) km(-1) at 1550 nm and to compensate the dispersion of standard fibers within +/- 0.5 ps nm(-1) km(-1) over a 100-nm range. The MOF dispersion properties have been studied by means of a numerical simulator for modal analysis based on the finite-element method.

Polarization splitter based on a square-lattice photonic-crystal fiber

A three-core polarization splitter based on a square-lattice photonic-crystal fiber is presented. The component separates the input field into two orthogonally polarized beams that are coupled to the horizontal and vertical output ports. The splitter has been designed through modal and beam propagation analysis by employing high-performance codes based on the finite-element method. Results obtained for a device length of 20 mm show extinction ratios as low as -23 dB with bandwidths as great as 90 nm.

Amplification properties of Er/sup 3+/-doped photonic crystal fibers

The amplification properties of different photonic crystal fibers have been studied by means of a full vector finite-element modal formulation combined with a population and propagation rate equation solver. A honeycomb as well as a cobweb photonic crystal fiber have been considered. The consequences of the defect dimension and the dopant radius on the field intensity distribution as well as the overlap integrals have been analyzed. Results demonstrate that a proper photonic crystal fiber design can be usefully exploited in order to obtain active fibers with superior characteristics compared to standard step index ones. In particular, photonic crystal fibers open up the possibility of a gain medium with highly flexible geometric, dispersion, and amplifying characteristics.

Toward A Highly Specific DNA Biosensor: PNA-Modified Suspended-Core Photonic Crystal Fibers

The feasibility of a biosensor for DNA detection based on suspended-core photonic crystal fibers is investigated. The possibility of functionalization of the hole surface, which allows DNA strand binding, is demonstrated, along with the selective detection of DNA through hybridization of immobilized peptide nucleic acid probes with their full-complementary and mismatched DNA segments.

Perturbation analysis of dispersion properties in photonic crystal fibers through the finite element method

Perturbations to the ideal cross section of photonic crystal fibers (PCFs) are introduced in order to investigate their performance as a function of the structural fluctuations which may occur during fabrication. The effects of the cross-section geometry perturbations on dispersion characteristics like dispersion parameter and differential group delay are presented and discussed. The analysis has been performed through the finite element method which assures high flexibility and high solution accuracy.

Single-mode regime of square-lattice photonic crystal fibers

The modal cutoff of square-lattice photonic crystal fibers with a finite number of air-hole rings has been accurately investigated to our knowledge for the first time. By analyzing the leaky behavior of the second-order mode, we have obtained a phase diagram that describes the regions of single-mode and multimode operation as well as the endlessly single-mode regime. Furthermore, starting from these results, we have obtained the cutoff normalized frequency according to two different formulations of the V parameter previously adopted for fibers with a triangular lattice. A final comparison of the cutoff properties of fibers characterized by a square lattice and a triangular lattice has been carried out.