Photonic Crystal Line-defect Waveguides Research Articles

Accurate modeling of line-defect photonic crystal waveguides

An accurate three-dimensional method to calculate the Bloch modes of photonic crystal (PhC) waveguides is proposed. Good agreement with available experimental and numerical data is obtained. The originality of the method lies in the fact that the Bloch modes are seen as the electromagnetic fields associated to the complex poles of an in-plane transversal scattering matrix. In comparison with previous approaches, the computational domain discretized is smaller and a higher accuracy for the losses of PhC waveguides is achieved.

Propagation losses of the fundamental mode in a single line-defect photonic crystal waveguide on an InP membrane

We have investigated light propagation through a single line-defect photonic crystal waveguide on a InP membrane. Modal analysis was performed using the finite-difference time-domain method. The fundamental mode has been found to be very close to the fundamental mode in a “refractive” waveguide but, in this case, it is inherently leaky. The propagation losses of this mode in the complete three-dimensional structure have been computed and measured to determine if its use could be of interest for practical applications. Propagation losses in the range of 0.1 dB/μm have been found numerically and experimentally for the fundamental mode whereas stronger out-of-plane losses have been observed for the other leaky mode within the band gap. The origins of the out-of-plane losses were then investigated and have clarified the inherent lower leakage of the fundamental mode.

Out-of-plane losses of line-defect photonic crystal waveguides

A numerical model is presented for computing the out-of-plane losses of a general class of two-dimensional photonic crystals superimposed. onto a slab confinement structure. The usefulness of this model is demonstrated by calculating the propagation loss of a single-row-defect waveguide composed of hexagonal air holes etched into two different slab structures. The results are interpreted in terms of a simple coupled-mode-theory picture in which loss is due to resonant coupling between the fundamental and certain radiative slab modes. These calculations show that low-loss photonic crystal waveguides should be possible by carefully designing the slab waveguide.

Singlemode lightwave transmission in SOI-type photonic-crystal line-defect waveguides with phase-shifted holes

Singlemode lightwave transmission was observed in novel line-defect photonic-crystal (PC) waveguides. The waveguide structure is constructed by adding phase-shifted holes in an ordinary missing-hole line defect. This device permits a fine singlemode lightwave transmission even though the waveguide structure is fabricated on silicon-on-insulator (SOI) substrate, which seriously promotes off-plane leakage of waveguiding modes.

Photonic crystal line defect waveguide directional coupler

A three-port directional coupler based on photonic crystal line defect waveguides is demonstrated. The directional coupler has only a 21 µm long coupling region. Wavelength-selecting operation around 1.5 µm wavelength was confirmed.

Singlemode transmission within photonic bandgap of width-varied single-line-defect photonic crystal waveguides on SOI substrates

It is demonstrated experimentally that a single missing-hole line defect photonic crystal waveguide fabricated on a silicon-on-insulator substrate can support a single waveguiding mode within the photonic bandgap if the waveguide width is properly tuned.