Mode density inside an omnidirectional mirror is heavily directional but not small

We show that ominidirectional ref lection is not a sufficient signature of a photonic bandgap. Although dramatic angular redistribution takes place, the mode density of the electromagnetic field is hardly altered within the ominidirectional ref lection range but rather has characteristics typical of a waveguide. The strikingly large polarization anisotropy is due to the huge dielectric contrast but not to a photonic bandgap

Dynamics of two capacitively coupled Josephson junctions in the overdamped limit

The dynamics of two capacitively coupled Josephson junctions are investigated analytically and numerically on the basis of the RSJ-model. The attention is focussed on nearly identical junctions with zero internal capacitance, the so-called overdamped limit. This is a common assumption for high-Tc junctions. Varying one of the control currents the dynamics shows the typical phenomenon of frequency locking and the corresponding devil’s staircase for a relevant range of system parameters and upper bounds for the widths of the locking regions in terms of the control currents are derived. Correspondingly, closer inspection reveals that below a certain value of the coupling capacitance the dynamics takes place on a two-dimensional torus in the phase space. Numerical evidence is found from the calculation of Poincaré sections, and more definitely, from Lyapunov exponents. Using the concept of normal hyperbolicity, a proof of the existence of an attracting two-torus is given. Above this value the torus and the devil’s staircase partially break up and chaotic dynamics appear in between the main steps of the staircase

Spontaneous emission rates inside an omni-directional mirror

Summary form only given. The omnidirectional mirror (ODM), which offers metallic-like reflection properties with much lower losses, was first reported in 1998 by Joannopoulos and coworkers and attracted a lot of attention. The omnidirectional reflection is due to a band of frequencies for which no propagation into the mirror is possible for any angle of incidence. The ODM is a special example of a Bragg mirror; it consists of alternating high and low index layers with almost equal optical thickness grown such that the dielectric contrast changes periodically on the scale of an optical wavelength. ODMs are often referred to as photonic band gap materials, because there is a range of frequencies for which no propagation is possible

Cornell Chronicle Vol. 20, No. 01 (August 25, 1988)

The Cornell Chronicle, a weekly news publication of Cornell University