Photonic Crystal Cavity

Photonic crystal (PhC) membrane cavities have been proposed for realizations of compact optical components in integrated photonics. Functionalities may include lasers, switches, or amplifiers. In this example, the fundamental mode in a L5 PhC membrane cavity is computed. The PhC slab consists of a thin dielectric membrane surrounded by air and perforated by circular pores on a regular, finite, hexagonal grid. For the L5 cavity, 5 pores along a line in the center of the device are omitted. Resonance modes are localized in the place of the missing pores. As the structure has three symmetry planes (x=0, y=0, z=0), the computational domain is chosen as 1/8 of the full structure, with mirror boundary conditions in the symmetry planes.

Parts of the mesh discretizing the L5 cavity geometry (blue: dielectric material, grey & omitted regions: air). The cavity is formed by the missing pores in the upper left part in this image. Light fields at a wavelength which is inside of the band gap of the surrounding finite photonic crystal are localized in the cavity.

The symmetry type of the desired resonances is specified within the project file (project.jcmp):

 Project {
   Electromagnetics {
      TimeHarmonic {
         ResonanceMode {
           FieldComponents = Electric
           MirrorSymmetry=[ElectricSymmetric,MagneticSymmetric,ElectricSymmetric]
           ...
         }
      }
   }
}

From the computed eigenvalue, the resonance wavelength of the computed mode as well as the quality factor (Q factor) of the mode are deduced in the run script run_project.m.

The computed eigenmode can be visualized and post-processed.

Near field intensity of the fundamental mode in a x-y-cross section. (computed with higher numerical accuracy than in project.jcmp)

Near field intensity of the fundamental mode in a x-z-cross section. (computed with higher numerical accuracy than in project.jcmp)