Stig Eigil Barkou

Silica–air photonic crystal fiber design that permits waveguiding by a true photonic bandgap effect

A theoretical investigation of a novel type of optical fiber is presented. The operation of the fiber relies entirely on wave guidance through the photonic bandgap effect and not on total internal reflection, thereby distinguishing that fiber from all other known fibers, including recently studied photonic crystal fibers. The novel fiber has a central low-index core region and a cladding consisting of a silica background material with air holes situated within a honeycomb lattice structure. We show the existence of photonic bandgaps for the silica-air cladding structure and demonstrate how light can be guided at the central low-index core region for a well-defined frequency that falls inside the photonic bandgap region of the cladding structure.

Highly increased photonic band gaps in silica/air structures

We explore the possibilities of achieving larger out-of-plane band gaps in two-dimensional silica/air photonic crystals with hexagonal symmetry. By modification of the basic hexagonal unit-cell, we demonstrate a new photonic crystal structure, for which the size of the band gaps is increased several times compared to those of simple hexagonal structures. The new structure allows design of silica/air photonic crystals exhibiting complete out-of-plane two-dimensional photonic band gaps for realistic fabrication parameters. We propose a new design of photonic crystal fibers based on the modified hexagonal structure. The advantages of the new design over recently fabricated photonic crystal fibers are discussed, and a calculation of a guided mode, localized at a low-index core region, is presented.

Waveguidance by the photonic bandgap effect in optical fibres

Photonic crystals form a new class of intriguing building blocks to be utilized in future optoelectronics and electromagnetics. One of the most exciting possibilities offered by photonic crystals is the realization of new types of electromagnetic waveguides. In the optical domain, the most mature technology for such photonic bandgap (PBG) waveguides is in optical fibre configurations. These new fibres can be classified in a fundamentally different way to all optical waveguides and possess radically different guiding properties due to PBG guidance, as opposed to guidance by total internal reflection. In this paper we summarize and review our theoretical work demonstrating the underlying physical principles of PBG guiding optical fibres and discuss some of their unique waveguiding properties.

Design of polarization-preserving photonic crystal fibres with elliptical pores

In this paper we discuss a microstructure of air capillaries with an elliptical cross section in a tread of glass, which gives an opportunity for the creation of a polarization-preserving fibre with very small beat length between the fundamental modes of different polarization. It is shown here that the fibre can be designed in such a way that only fundamental modes are guided. However, it is not possible with this process to create a photonic crystal fibre which can guide only one fundamental mode.

Suppression of spontaneous emission for a two-dimensional honeycomb photonic bandgap structure estimated using a new effective-index model

The suppression of spontaneous emission introduced by a two-dimensional honeycomb-rod photonic bandgap structure is evaluated using the plane-wave expansion theory. An analysis of the out-of-plane angle dependency on the photonic bandgaps through the application of a new effective refractive-index model is presented. The in-plane properties for structures characterized by a rod dielectric constant in the range from 1.0 to 15.0, air background, and a filling fraction in the range from 0.07 to 0.4 are analyzed, and a structure with a relative in-plane bandgap of 10% is chosen. The out-of-plane angle analysis is performed for this structure, and it is found that propagation for modes within a narrow frequency interval is inhibited for a solid angle of 2.16 /spl pi/, covering 54% of the spontaneous emission from a narrow-linewidth point source.

Polarization properties of photonic bandgap fibers

We present the first analysis of polarization properties of photonic bandgap fibers. Strong birefringence may be obtained for modest non-uniformities in and around the core region, suggesting the use of photonic bandgap fibers as polarization maintaining components.

Polarization properties of honeycomb-structured photonic bandgap fibres

New polarization properties of photonic bandgap optical fibres are analysed. Exemplified by an analysis of honeycomb-structured photonic bandgap fibres, strong birefringence is found for modest non-uniformities (deviations from the 60° symmetry) in and around the core region. This suggests the application of photonic bandgap fibres as polarization-maintaining optical components.

Two-dimensional Kagome photonic bandgap waveguide

The transverse-magnetic photonic-bandgap-guidance properties are investigated for a planar two-dimensional (2-D) Kagome waveguide configuration using a full-vectorial plane-wave-expansion method. Single-moded well-localized low-index guided modes are found. The localization of the optical modes is investigated with respect to the width of the 2D Kagome waveguide, and the number of modes existing for specific frequencies and waveguide widths is mapped out.

Photonic bandgap fibers

Photonic bandgap fibers are described using a new Kagome cladding structure. These fibers may potentially guide light in low-index regions. Such fibers offer new dispersion properties, and large design flexibility.

Macro-bending loss estimation for air-guiding photonic crystal fibres

Optical fibres operating by the photonic bandgap effect offers an alternative approach to evanescent field waveguides for opticai sensing applications. In addition to this, these photonic crystal fibres provide completely new waveguiding properties, which include different macro-bending loss performance compared to standard optical fibres. A first estimation of these new properties is demonstrated for air-guiding fibre designs by combining accurate vectorial mode analysis and an adaptation of more traditional macro-bending loss theory.