constant (k₀) and propagation direction (?₀ & ?₀) - until a combination is found which drives the determinant of the matrix to zero. Equation has been used to compute bands in various types of doped and undoped photonic crystals. Not surprisingly, doping photonic crystals with defects provides a means for designing photonic passbands, in just the same way that doping semiconductors with chemical impurities provides a means for designing electronic passbands.

For