We theoretically investigate the design of cavities in athree-dimensional (3D) inverse woodpile photonic crystal. This class ofcubic diamond-like crystals has a very broad photonic band gap andconsists of two perpendicular arrays of pores with a rectangularstructure. The point defect that acts as a cavity is centred on theintersection of two intersecting perpendicular pores with a radius thatdiffers from the ones in the bulk of the crystal. We have performedsupercell bandstructure calculations with up to 555 unit cells. We findthat up to five isolated and dispersionless bands appear within the 3Dphotonic band gap. For each isolated band, the electric-field energy islocalized in a volume centred on the point defect, hence the pointdefect acts as a 3D photonic band gap cavity. The mode volume of thecavities resonances is as small as 0.8 λ^3 (resonance wavelengthcubed), indicating a strong confinement of the light. By varying theradius of the defect pores we found that only donor-like resonancesappear for smaller defect radius, whereas no acceptor-like resonancesappear for greater defect radius. From a 3D plot of the distribution ofthe electric-field energy density we conclude that peaks of energy foundin sharp edges situated at the point defect, similar to how electronscollect at such features. This is different from what is observed forcavities in non-inverted woodpile structures. Since inverse woodpilecrystals can be fabricated from silicon by CMOS-compatible means, weproject that single cavities and even cavity arrays can be realized, forwavelength ranges compatible with telecommunication windows in the nearinfrared.

http://dx.doi.org/10.1103/PhysRevB.90.115140

L. A. Woldering, A. P. Mosk, and W. L. Vos

2014

09/2014

Phys. Rev. B

90

115140: 1-9

3D photonic band gap, cavity, nanostructure, photonic crystal