Density of states of slab photonic crystals and the laser oscillation in photonic crystals

A treatment of the density of states of electromagnetic normal modes of sla b photonic crystals is given to illustrate the thickness dependence of the Q values of the slab modes of arrayed dielectric spheres. The onset of the laser oscillation is then examined for a slab photonic crystal of arrayed c ylinders by simulating active cylinders as having a complex dielectric cons tant of negative imaginary part gamma. It is shown that the divergence of t he transmittivity of light occurs as an indication of the onset of lasing, when the slab is thick enough to give high Q values to the slab modes. The threshold value of gamma is discussed in comparison with a one-dimensional (1-D) multilayer stack of thin films.