N. Somasiri

Design and characterization of compact single-section passive polarization rotator

In this paper an improved design for a short and low-loss polarization rotator is proposed, consisting of a single-section asymmetrical waveguide butt-coupled between two standard rib waveguides. At a wavelength of 1.55 /spl mu/m, nearly 100% polarization conversion ratio is obtained, with a relatively short (320 /spl mu/m) device length and an extremely low 0.5 dB total insertion loss. The simulation results are obtained using the full vectorial finite-element-based beam propagation, the junction analysis, and the modal solution approaches.

Full vectorial finite element modeling of novel polarization rotators

In this paper, the numerically efficient finite element based full vectorial modal and propagation approaches are used in order to analyze and design single and multiple sectioned passive polarization rotators (PRs). The effects of different waveguide parameters, such as the waveguide width, etching depth, sidewall slant angle and refractive index contrast on the PR performance in terms of polarization conversion efficiency, section length and losses are investigated in detail in order to obtain optimum PR designs. Moreover, a thorough sensitivity study of the fabrication tolerances and the operating wavelength on the performance of the PRs has also been carried out.

Polarization crosstalk in high index contrast planar silica waveguides with slanted sidewalls

Numerically simulated results, by using rigorous full vectorial approaches, indicate the possibility of significant polarization crosstalk in a high index contrast planar silica waveguide, particularly when the sidewalls are not exactly vertical.

Fabrication tolerance study of a compact passive polarization rotator

In this paper, the expected performance of a compact low-loss passive polarization rotator is reported by using rigorous numerical approaches. The effects of waveguide width, slant angle, etch depth, and refractive index variations during its fabrication on the overall polarization conversion and polarization crosstalk are reported. It is also expected that over the 1.53to 1.61-/spl mu/m wavelength range, polarization conversion would be more than 99% and polarization crosstalk would be better than -20 dB.

Polarization crosstalk in high index contrast planar silica waveguides

Polarization crosstalk and the effect of the waveguide sidewall slope angle in a planar silica waveguide with high index contrast is calculated by using rigorous full vectorial numerical approaches.

Birefringence compensation of silica waveguides

A novel method of compensating stress-induced birefringence in silica waveguides by incorporating a layered structure is introduced and analyzed by using a numerically efficient, vectorial H-field finite element-based modal solution approach.

Characterization of high-index contrast Silica guided-wave devices

Modal properties of silica waveguides are presented along with their results on single mode operation, spot-size variations, confinement factor and, modal field profiles for different index contrast value between the core and the claddings. Both dominat and non-dominat field profiles and their transverse variations are also shown. Numerically simulated results also suggests that by using the MM-based design a very compact optical power splitter, of the order of 500 μm in length, can be designed, which is much shorter than conventional directional coupler or Y-junction-based designs.

Rigorous analysis of photonic crystal fibers by using a full vectorial H-field-based finite element method

Modal solutions for photonic crystal fibers with circular air-holes in a hexagonal array are presented, by using a rigorous full-vectorial finite element-based approach. The effective indices, mode field profiles, spot-sizes, modal hybridness, modal birefringence and group velocity dispersion values are presented. The effect of external pressure on photonic crystal fibers is analyzed also by using the powerful finite element method. Modal solutions are obtained for both symmetric and asymmetric air-holes and the effect of pressure on the modal properties and mode degeneration are evaluated, presented and discussed.

Polarization issues in optoelectronic devices and systems

Many integrated optical-based subsystems incorporate optical guided-wave devices and connecting optical waveguides with two-dimensional confinement and a high index contrast. The modes present in such waveguides and devices are not purely of the TE or TM type but hybrid in nature, with all the six components of the electric and magnetic fields being present. Over the last three decades, many semi-analytical and numerical approaches have been developed to study the modes in optical waveguide structures: however, to characterize polarization issues in such systems, a fully vectorial approach is necessary. In that respect the fully vectorial H-field based finite element method (FEM) [1] is one of the most rigorous and versatile of the approaches. The main advantage of the FEM over many other methods is its more accurate representation of the waveguide cross-section. In an optoelectronic system, when modes are hybrid in nature, polarization conversion can take place in the optical system, either unintentionally or deliberately at different waveguide junctions. The least squares boundary residual method [2], which is a fully vectorial and rigorously convergent method, is also used here to characterize optoelectronic systems. The beam propagation method (BPM) is field evolutionary in its approach and a versatile method for the characterization of a z-dependent guided-wave structure. A numerically efficient full-vectorial FEM-based BPM [3] has been developed to characterize z-dependent guided-wave devices. Results for the polarization cross-talk in such systems will be presented, along with their various minimization approaches. Results will also be presented for the design optimization of various compact polarization rotators using cascaded sections with or without a slanted side wall and also with curved waveguide sections.

Polarization issues in optoelectronic systems

In this paper, the numerically efficient finite element based full vectorial modal and propagation approaches are used to design and optimize various photonic components for the manipulation of polarization effects in opto-electronic systems. Designs of directional coupler-based polarization splitters both using a metal cladding and without a metal cladding are presented. It is also shown that a compact polarization splitters both using a metal cladding and without a metal cladding are presented. It is also shown that a compact polarization splitter can be designed by using single section or two-section multimode interference (MMI) guides. In this paper, a novel concept of a single polarization optical waveguide with layered core is introduced and its expected performance is reported, along with its experimental validation. In this paper, the origin of polarization cross-talk and design approaches to minimize its detrimental effects is also presented. Finally, designs of single and multiple sectioned passive polarization rotators using waveguides with slanted side-walls are also presented.