Ultra high-Q photonic crystal nanocavity design: The effect of a low-epsilon slab material

TL;DR

This paper investigates how the dielectric constant of the slab material affects the quality factor in photonic crystal nanocavities, comparing silicon and diamond, and presents designs achieving ultra high-Q factors.

Contribution

It provides an analytical framework and design strategies for optimizing high-Q photonic crystal cavities using low-epsilon materials like diamond.

Findings

High Q achieved with silicon and diamond slabs.

Q=2.6×10^5 in double heterostructure design.

Q=1.3×10^6 with optimized local width modulation.

Abstract

We analyze the influence of the dielectric constant of the slab on the quality factor (Q) in slab photonic crystal cavities with a minimized vertical losses model. The higher value of Q in high-epsilon cavity is attributed to the lower mode frequency. The Q ratio in a high-epsilon (silicon) vs. low-epsilon (diamond) slab is examined as a function of mode volume (Vm). The mode volume compensation technique is discussed. Finally, diamond cavity design is addressed. The analytical results are compared to 3D FDTD calculations. In a double heterostructure design, a Q=2.6*10^5 is obtained. The highest Q=1.3*10^6 with Vm=1.77*(lambda/n)^3 in a local width modulation design is derived.