A
photonic bandgap device has a lattice structure, with a
waveguide formed by a mesh of defects in the lattice, the defects being located discontinuously, but sufficiently close to each other to provide
coupling between overlapping evanescent defect
modes. By changing shape and configuration of the mesh and varying the types of defects, it is easier to control the width and position of the transmission band, in
wavelength terms, compared to a
waveguide formed only from a planar defect, i.e. a
single line of defects. Multiplexers, demultiplexers, filters, switches, combiners, and splitters may be created. Many devices and different types of devices can be integrated onto the same
crystal lattice, with far greater compactness than planar
waveguide technology. The mesh can have a periodic structure of lines of defects, or periodic spacing between defects to reduce loss.