In Slotted Photonic Crystal (SPhCs) devices the light is squeezed, confined and guided through air cuts realized in a Photonic Crystal (PhC) background. This confining mechanism is based on both the total internal reflection (experienced by the field at the discontinuous edges of the slot) and the resonant confinement offered by the periodicity of the Photonic Crystal. Figure 1 shows the SEM picture of a typical slotted PhC waveguide. In this structures light is confined in extremely reduced volumes, hence with a significant intensity. The narrow air features can then be infiltrated with media spanning from gas to biological analytes to nonlinear and/or active material to take advantage of the increased overlap between the electromagnetic field and the material relevant to the specific application.
SPhCs support slow light propagation and in general allow dispersion management of light propagating mainly in air. We also have reported on the design, fabrication and characterization of slotted PhC cavities based on the heterostructure approach. We demonstrate record quality factor of up to 50K for air based cavities and unprecedented detection limit (DL = 7.8e-6 RIU) for an integrated biosensor based on them.
In general, slotted PhC waveguides and cavities are a generic and flexible host for applications requiring highly efficient light-matter interactions.