Beam-quality factor of single-mode gain-guided fiber lasers.

The beam-quality factor M(2) for the fundamental LP01 mode of a step-index fiber is calculated in the presence of gain, in a closed form, as a function of the complex generalized V number. It is shown that the M(2) value of a single-mode gain-guided fiber laser can be arbitrarily large. The results are important for the interpretation of the beam-quality measurements in recent experiments on single-mode gain-guided fiber lasers.

Constrained least squares Fourier modal method for computing scattering from metallic binary gratings.

In a recent article [J. Opt. Soc.

Reliable computation of scattering from metallic binary gratings using Fourier-based modal methods.

Convergence problems in modal methods for TM polarized fields are often attributed to the inaccuracies in computing the modes of a grating. We report that even in the absence of these inaccuracies convergence problems persist. These arise because of the truncation of the infinite set of linear equations resulting from matching the fields at the grating-substrate and grating-superstrate interfaces with a square matrix.

Mode shaping in multicore fibers.

We propose a novel multicore fiber design strategy for obtaining a flat in-phase supermode that optimizes utilization of the active medium inversion in the multiple cores. The spatially flat supermode is achieved by engineering the fiber so that the total mutual coupling between neighboring active cores is equal. Different designs suitable for different fabrication processes, such as stack-and-draw and drilling, are proposed.

Ultra-flattened-dispersion selectively liquid-filled photonic crystal fibers.

We propose a method to control the chromatic dispersion properties of photonic crystal fibers using the selective hole filling technique. The method is based on a single hole-size fiber geometry, and uses an appropriate index-matching liquid to modify the effective size of the filled holes. The dependence of dispersion properties of the fiber on the design parameters such as the refractive index of the liquid, lattice constant and hole diameter are studied numerically.