Density of states in 1D disordered photonic crystals: Analytical solution

A novel analytical approach to the calculation of the density of states of one-dimensional disordered photonic crystals has been developed. It is shown that the problem can be reduced to the solution of a stationary Fokker–Planck equation for the distribution function of a reduced phase variable Ψ which is directly related to the quantity ( d E / d z ) / E where E ( z ) is the electric field of the electromagnetic wave and z the position in the structure. We have obtained an analytical expression for the density of states within and close to the first photonic band gap and have examined various approximations. Our analytical expressions for the density of states are in good agreement with the results of direct numerical calculations.